# NASASpaceFlight.com Forum

## Robotic Spacecraft (Astronomy, Planetary, Earth, Solar/Heliophysics) => Space Science Coverage => Topic started by: Star One on 01/22/2017 07:27 PM

Post by: Star One on 01/22/2017 07:27 PM
Seemed a good idea to have a separate thread for miscellaneous exoplanet discoveries.

Is there a circumbinary planet around NSVS 14256825?

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The cyclic behaviour of (O-C) residuals of eclipse timings in the sdB+M eclipsing binary NSVS 14256825 was previously attributed to one or two Jovian-type circumbinary planets. We report 83 new eclipse timings that not only fill in the gaps in those already published but also extend the time span of the (O-C) diagram by three years. Based on the archival and our new data spanning over more than 17 years we re-examined the up to date system (O-C). The data revealed systematic, quasi-sinusoidal variation deviating from an older linear ephemeris by about 100 s. It also exhibits a maximum in the (O-C) near JD 2,456,400 that was previously unknown. We consider two most credible explanations of the (O-C) variability: the light propagation time due to the presence of an invisible companion in a distant circumbinary orbit, and magnetic cycles reshaping one of the binary components, known as the Applegate or Lanza-Rodono effect. We found that the latter mechanism is unlikely due to the insufficient energy budget of the M-dwarf secondary. In the framework of the third-body hypothesis, we obtained meaningful constraints on the Keplerian parameters of a putative companion and its mass. Our best-fitting model indicates that the observed quasi-periodic (O-C) variability can be explained by the presence of a brown dwarf with the minimal mass of 15 Jupiter masses rather than a planet, orbiting the binary in a moderately elliptical orbit (~ 0.175) with the period of ~ 10 years. Our analysis rules out two planets model proposed earlier.

https://arxiv.org/abs/1701.05211
Post by: Star One on 01/26/2017 06:54 PM
Wolf 1061 unlikely to host habitable worlds.

http://www.centauri-dreams.org/?p=37016

Here's the pre-print.

Characterization of the Wolf 1061 Planetary System

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A critical component of exoplanetary studies is an exhaustive characterization of the host star, from which the planetary properties are frequently derived. Of particular value are the radius, temperature, and luminosity, which are key stellar parameters for studies of transit and habitability science. Here we present the results of new observations of Wolf~1061, known to host three super-Earths. Our observations from the Center for High Angular Resolution Astronomy (CHARA) interferometric array provide a direct stellar radius measurement of 0.3207±0.0088~R⊙, from which we calculate the effective temperature and luminosity using spectral energy distribution models. We obtained seven years of precise, automated photometry that reveals the correct stellar rotation period of 89.3±1.8~days, finds no evidence of photometric transits, and confirms the radial velocity signals are not due to stellar activity. Finally, our stellar properties are used to calculate the extent of the Habitable Zone for the Wolf~1061 system, for which the optimistic boundaries are 0.09--0.23~AU. Our simulations of the planetary orbital dynamics shows that the eccentricity of the Habitable Zone planet oscillates to values as high as ∼0.15 as it exchanges angular momentum with the other planets in the system.

https://arxiv.org/abs/1612.0934
Post by: ikke666 on 01/27/2017 04:59 PM
is there a list of stars that have planets on web?  ::) prefably with the kind of planet (gas giant, earth like,...)
Post by: testguy on 01/27/2017 05:29 PM

http://exoplanet.eu/catalog/
Post by: hop on 01/28/2017 06:00 AM
There's also the NASA Exoplanet archive http://exoplanetarchive.ipac.caltech.edu/
Post by: Star One on 01/28/2017 12:13 PM
Took the Keck observatory seven years of observations to produce this.

A Four Planet System in Orbit, Directly Imaged and Remarkable

http://www.manyworlds.space/index.php/2017/01/24/a-four-planet-system-in-orbit-directly-imaged-and-remarkable/
Post by: ikke666 on 01/28/2017 03:55 PM
thanks for the sites  ;D
Post by: Star One on 02/02/2017 08:38 PM
Water spotted in the atmosphere of nearby hot Jupiter exoplanet

https://www.newscientist.com/article/mg23331111-800-water-spotted-in-the-atmosphere-of-nearby-hot-jupiter-exoplanet/
Post by: Star One on 02/13/2017 07:36 PM
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Washington, DC— An international team of astronomers released the largest-ever compilation of exoplanet-detecting observations made using a technique called the radial velocity method. They demonstrated how these observations can be used to hunt for planets by detecting more than 100 potential exoplanets, including one orbiting the fourth-closest star to our own Solar System, which is about 8.1 light years away from Earth. The paper is published in The Astronomical Journal.
The radial velocity method is one of the most successful techniques for finding and confirming planets. It takes advantage of the fact that in addition to a planet being influenced by the gravity of the star it orbits, the planet’s gravity also affects the star. Astronomers are able to use sophisticated tools to detect the tiny wobble the planet induces as its gravity tugs on the star.
The virtual mountain of data released to the public in this paper was gathered as part of a two-decade radial velocity planet-hunting program that uses a spectrometer called HIRES, mounted on the 10-meter Keck-I telescope of the W.M. Keck Observatory atop Mauna Kea in Hawaii. The compilation includes almost 61,000 individual measurements made of more than 1,600 stars. By making the data public, the team is offering unprecedented access to one of the best exoplanet searches in the world.
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One of these probable planets is around a star called GJ 411, also known as Lalande 21185. It is the fourth-closest star to our own Sun and is only about 40 percent the mass of the Sun. The planet has a very short orbital period of just under 10 days, so it is no Earth-twin. However, the inferred planet, GJ 411b, continues a trend that has been seen in the overall population of detected exoplanets: the smallest planets are found around the smallest stars.

https://carnegiescience.edu/news/team-makes-planet-hunting-group-effort-finds-more-100-candidates#
Post by: Star One on 02/15/2017 07:11 PM
Planet-Induced Stellar Pulsations in HAT-P-2's Eccentric System

J. de Wit, N.K. Lewis, H.A. Knutson, J. Fuller, V. Antoci, B.J. Fulton, G. Laughlin, D. Deming, A. Shporer, K. Batygin, N.B. Cowan, E. Agol, A.S. Burrows, J.J. Fortney, J. Langton, A.P. Showman
(Submitted on 13 Feb 2017)

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Extrasolar planets on eccentric short-period orbits provide a laboratory in which to study radiative and tidal interactions between a planet and its host star under extreme forcing conditions. Studying such systems probes how the planet's atmosphere redistributes the time-varying heat flux from its host and how the host star responds to transient tidal distortion. Here, we report the insights into the planet-star interactions in HAT-P-2's eccentric planetary system gained from the analysis of 350 hr of 4.5 micron observations with the Spitzer Space Telescope. The observations show no sign of orbit-to-orbit variability nor of orbital evolution of the eccentric planetary companion, HAT-P-2 b. The extensive coverage allows us to better differentiate instrumental systematics from the transient heating of HAT-P-2 b's 4.5 micron photosphere and yields the detection of stellar pulsations with an amplitude of approximately 40 ppm. These pulsation modes correspond to exact harmonics of the planet's orbital frequency, indicative of a tidal origin. Transient tidal effects can excite pulsation modes in the envelope of a star, but, to date, such pulsations had only been detected in highly eccentric stellar binaries. Current stellar models are unable to reproduce HAT-P-2's pulsations, suggesting that our understanding of the interactions at play in this system is incomplete.

https://arxiv.org/abs/1702.03797

We need your help on a brand new astronomy project – Backyard Worlds: Planet 9
In this project you’ll be searching through images from NASA’s Wide-field Infrared Survey Explorer (WISE) mission, hunting for objects such as brown dwarfs and low-mass stars in our Solar System’s neighbourhood. You may find an object closer than Proxima Centauri (the closest star to the Sun) or even discover the Sun’s hypothesized ninth planet, which models suggest might appear in these images!
Start hunting right now at www.backyardworlds.org.
Post by: Mongo62 on 02/28/2017 07:23 PM
Towards Detection of Exoplanetary Rings Via Transit Photometry: Methodology and a Possible Candidate (https://arxiv.org/abs/1702.08252)

Abstract: Detection of a planetary ring of exoplanets remains as one of the most attractive but challenging goals in the field. We present a methodology of a systematic search for exoplanetary rings via transit photometry of long-period planets. The methodology relies on a precise integration scheme we develop to compute a transit light curve of a ringed planet. We apply the methodology to 89 long-period planet candidates from the Kepler data so as to estimate, and/or set upper limits on, the parameters of possible rings. While a majority of our samples do not have a sufficiently good signal-to-noise ratio for meaningful constraints on ring parameters, we find that six systems with a higher signal-to-noise ratio are inconsistent with the presence of a ring larger than 1.5 times the planetary radius assuming a grazing orbit and a tilted ring. Furthermore, we identify five preliminary candidate systems whose light curves exhibit ring-like features. After removing four false positives due to the contamination from nearby stars, we identify KIC 10403228 as a reasonable candidate for a ringed planet. A systematic parameter fit of its light curve with a ringed planet model indicates two possible solutions corresponding to a Saturn-like planet with a tilted ring. There also remain other two possible scenarios accounting for the data; a circumstellar disk and a hierarchical triple. Due to large uncertain factors, we cannot choose one specific model among the three.
Post by: Star One on 03/10/2017 06:51 PM
Another close by system that may turn out to be suitable for exo-atmosphere observations.

HD 219134: A Nearby System with Multiple Transits

http://www.centauri-dreams.org/?p=37300

Here's the paper.

http://www.nature.com/articles/s41550-017-0056#references
Post by: jebbo on 03/13/2017 05:24 PM
In news other than Trappist-1, this on Kepler-444 is interesting:

https://arxiv.org/abs/1703.03417 (https://arxiv.org/abs/1703.03417)

The masses imply a density around that of water, which is quite remarkable as the planets have been at >600K for about 11 billion years ... so keeping hold of volatiles is quite a feat. Oh, it also implies an origin beyond the ice line

--- Tony
Post by: Bynaus on 03/13/2017 05:36 PM
Only the nominal densities are close to water, the uncertainties are quite high. Within only one standard deviation (68% confidence interval), the densities are between 0.5 g/cm3 and 3.5 g/cm3 (see Table 2), so a rocky composition can certainly not be excluded at this point. Like you say, it would be very surprising if such low-mass planets would have kept their volatiles at 600 K over the 11 Ga age of the system.
Post by: jebbo on 03/13/2017 05:42 PM
Absolutely ... and I'm wary of numbers from Bayesian methods (e.g. see Kass & Rafferty, 1995)

Shame the predicted RV is too low, though I wonder if at magnitude 9, we might get transmission spectroscopy

Edit: added figure from arxiv.org paper
--- Tony
Post by: Star One on 03/13/2017 08:10 PM
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The search for extraterrestrial life is increasingly informed by our knowledge of exoplanets. Within three decades, we may know whether extrasolar life is rare.

Post by: Star One on 03/14/2017 11:10 AM
Mysterious celestial object could be an elusive brown dwarf or a free-floating planet

The object is not part of the AB Doradus moving group, as previous hypothesised.

http://www.ibtimes.co.uk/mysterious-celestial-object-could-be-elusive-brown-dwarf-free-floating-planet-1611441

More details on this topic in this article including the relevant paper.

https://phys.org/news/2017-03-mysterious-isolated-astronomers.html
Post by: Star One on 03/15/2017 08:11 PM
Not an exoplanet but an interesting star instead.

Isotope shift and search for metastable superheavy elements in astrophysical

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Spectral lines belonging to the short-lifetime heavy radioactive elements up to Es (Z=99) have been found in the spectra of the Przybylski's star. We suggest that these unstable elements may be decay products of a "magic" metastable nucleus belonging to the the island of stability where the nuclei have a magic number of neutrons N=184. The laboratory-produced nuclei have a significantly smaller number of neutrons. To identify spectra of the N=184 isotopes of these nuclei and their neutron-reach superheavy decay products in astrophysical data we calculate the isotope shift which should be added to the laboratory - measured wavelenghs. The results for the isotopic shifts in the strongest optical electromagnetic transitions in No, Lr, Nh, Fl,and Z=120 elements are presented.

https://arxiv.org/abs/1703.04250
Post by: Bynaus on 03/17/2017 06:20 AM
Plenty of Earth-mass worlds around nearby red dwarfs (one of them in the HZ, 3.8 pc away).

https://arxiv.org/abs/1703.05386

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The HARPS search for southern extra-solar planets XLI. A dozen planets around the M dwarfs GJ 3138, GJ 3323, GJ 273, GJ 628, and GJ 3293

Context. Low mass stars are currently the best targets for searches for rocky planets in the habitable zone of their host star. Over the last 13 years, precise radial velocities measured with the HARPS spectrograph have identified over a dozen super-Earths and Earth-mass planets (msin i<10Mearth ) around M dwarfs, with a well understood selection function. This well defined sample informs on their frequency of occurrence and on the distribution of their orbital parameters, and therefore already constrains our understanding of planetary formation. The subset of these low-mass planets that were found within the habitable zone of their host star also provide prized targets for future atmospheric biomarkers searches. Aims. We are working to extend this planetary sample to lower masses and longer periods through dense and long-term monitoring of the radial velocity of a small M dwarf sample. Methods. We obtained large numbers of HARPS spectra for the M dwarfs GJ 3138, GJ 3323, GJ 273, GJ 628 and GJ 3293, from which we derived radial velocities (RVs) and spectroscopic activity indicators. We searched them for variabilities, periodicities, Keplerian modulations and correlations, and attribute the radial-velocity variations to combinations of planetary companions and stellar activity. Results. We detect 12 planets, of which 9 are new with masses ranging from 1.17 to 10.5 Mearth . Those planets have relatively short orbital periods (P<40 d), except two of them with periods of 217.6 and 257.8 days. Among these systems, GJ 273 harbor two planets with masses close to the one of the Earth. With a distance of 3.8 parsec only, GJ 273 is the second nearest known planetary system - after Proxima Centauri - with a planet orbiting the circumstellar habitable zone.

I know we already know this from Kepler, but its really astonishing how these red dwarf star systems are all choke full with massive terrestrial-to-neptunian worlds.

GJ 273 - also known as Luyten's Star - is currently located only 1.2 LY away from Procyon. It has a ca. 3 Earth-mass planet which recieves 1.06 times the solar insolation on Earth.
Post by: Star One on 03/28/2017 08:17 PM
Jason Wright investigates Przybylski’s Star.

http://sites.psu.edu/astrowright/2017/03/15/przybylskis-star-i-whats-that/
Post by: CuddlyRocket on 03/31/2017 11:55 AM
Eric Mamajek‏
@EricMamajek

Fig. 7 will make #exoplanet jaws drop https://arxiv.org/abs/1703.10375 "Fulton Gap" clearly separates super-Earths & sub-Neptunes #Kepler #Keck #NASA

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We find evidence for a bimodal distribution of small planet sizes. Sub-Neptunes and super-Earths appear to be two distinct planet classes. Planets tend to prefer radii of either ∼1.3 R⊕ or ∼2.4 R⊕, with relatively few planets having radii of 1.5–2.0 R⊕.
Post by: Star One on 04/04/2017 08:35 PM
Venus 2.0 Discovered In Our Own Backyard

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And now, a team of international astronomers has announced the discovery of an extra-solar body that is similar to another terrestrial planet in our own Solar System. It’s known as Kepler-1649b, a planet that appears to be similar in size and density to Earth and is located in a star system just 219 light-years away. But in terms of its atmosphere, this planet appears to be decidedly more “Venus-like” (i.e. insanely hot!)

The team’s study, titled “Kepler-1649b: An Exo-Venus in the Solar Neighborhood“, was recently published in The Astronomical Journal. Led by Isabel Angelo – of the SETI Institute, NASA Ames Research Center, and UC Berkley – the team included researchers also from SETI and Ames, as well as the NASA Exoplanet Science Institute (NExScl), the Exoplanet Research Institute (iREx), the Center for Astrophysics Research, and other research institutions.

https://www.universetoday.com/134849/venus-2-0-discovered-back-yard/
Post by: Star One on 04/06/2017 08:26 PM
Atmosphere around super-Earth detected

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Astronomers have detected an atmosphere around the super-Earth GJ 1132b. This marks the first detection of an atmosphere around a low-mass super-Earth, in terms of radius and mass the most Earth-like planet around which an atmosphere has yet been detected. Thus, this is a significant step on the path towards the detection of life on an exoplanet. The team, which includes researchers from the Max Planck Institute for Astronomy, used the 2.2-m ESO/MPG telescope in Chile to take images of the planet's host star, GJ 1132, and measured the slight decrease in brightness as the planet and its atmosphere absorbed some of the starlight while passing directly in front of their host star.

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The team used the GROND imager at the 2.2-m ESO/MPG telescope of the European Southern Observatory in Chile to observe the planet simultaneously in seven different wavelength bands. GJ 1132b is a transiting planet: From the perspective of an observer on Earth, it passes directly in front of its star every 1.6 days, blocking some of the star's light.

The size of stars like GJ 1132 is well known from stellar models. From the fraction of starlight blocked by the planet, astronomers can deduce the planet's size—in this case around 1.4 times the size of the Earth. Crucially, the new observations showed the planet to be larger at one of the infrared wavelengths than at the others. This suggests the presence of an atmosphere that is opaque to this specific infrared light (making the planet appear larger) but transparent at all the others. Different possible versions of the atmosphere were then simulated by team members at the University of Cambridge and the Max Planck Institute for Astronomy. According to those models, an atmosphere rich in water and methane would explain the observations very well.

The discovery comes with the usual exoplanet caveats: while somewhat larger than Earth, and with 1.6 times Earth's mass (as determined by earlier measurements), observations to date do not provide sufficient data to decide how similar or dissimilar GJ 1132b is to Earth. Possibilities include a "water world" with an atmosphere of hot steam.

The presence of the atmosphere is a reason for cautious optimism. M dwarfs are the most common types of star, and show high levels of activity; for some set-ups, this activity (in the shape of flares and particle streams) can be expected to blow away nearby planets' atmospheres. GJ 1132b provides a hopeful counterexample of an atmosphere that has endured for billion of years (that is, long enough for us to detect it). Given the great number of M dwarf stars, such atmospheres could mean that the preconditions for life are quite common in the universe.

In any case, the new observations make GJ 1132b a high-priority target for further study by instruments such as the Hubble Space Telescope, ESO's Very Large Telescope, and the James Webb Space Telescope slated for launch in 2018.

https://m.phys.org/news/2017-04-atmosphere-super-earth.html

Stargazing Live viewers find four-planet solar system via crowd-sourcing project

http://mobile.abc.net.au/news/2017-04-06/stargazing-live-four-planets-discovered-in-new-solar-system/8423142
Post by: CuddlyRocket on 04/06/2017 10:20 PM
Stargazing Live viewers find four-planet solar system via crowd-sourcing project

http://mobile.abc.net.au/news/2017-04-06/stargazing-live-four-planets-discovered-in-new-solar-system/8423142

Interesting 3:2 orbital resonances between planets b and c, c and d, and d and e.
Post by: jebbo on 04/07/2017 08:50 AM
Interesting 3:2 orbital resonances between planets b and c, c and d, and d and e.

A very interesting compact system around a late G dwarf, which makes these planets *hot*.  Sadly, no observed TTVs so it will be a while before we know mass/density.

Worth noting this was from the Campaign 12 raw cadence data (the processed data has not yet been released to MAST).  I'm hoping this sets a precedent for future campaigns :-)

This weekend, I'll try and produce a light curve for this one (but my raw cadence code still needs a fair bit of debug).

There are quite a few new candidates from this Exoplanet Explorers search, some in earlier quarters, so once again, the human eyeball has found things missed by the automated pipelines.  Clearly some will be false positives (BGEB contamination is most likely).

Edit: taking much longer than expected as the MAST download of the raw cadence data is glacial.

--- Tony
Post by: CuddlyRocket on 04/17/2017 08:01 AM
Cross-posting from the 'NASA's Trappist-1 Announcement - Feb 22, 2017' thread.

Updated Masses for the TRAPPIST-1 Planets (arXiv) (https://arxiv.org/abs/1704.04290)

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The newly detected TRAPPIST-1 system, with seven low-mass, roughly Earth-sized planets transiting a nearby ultra-cool dwarf, is one of the most important exoplanet discoveries to date. The short baseline of the available discovery observations, however, means that the planetary masses (obtained through measurement of transit timing variations of the planets of the system) are not yet well constrained. The masses reported in the discovery paper were derived using a combination of photometric timing measurements obtained from the ground and from the Spitzer spacecraft, and have uncertainties ranging from 30\% to nearly 100\%, with the mass of the outermost, P=18.8d, planet h remaining unmeasured. Here, we present an analysis that supplements the timing measurements of the discovery paper with 73.6 days of photometry obtained by the K2 Mission. Our analysis refines the orbital parameters for all of the planets in the system. We substantially improve the upper bounds on eccentricity for inner six planets (finding e<0.02 for inner six known members of the system), and we derive masses of 0.79±0.27M⊕, 1.63±0.63M⊕, 0.33±0.15M⊕, 0.24+0.56−0.24M⊕, 0.36±0.12M⊕, 0.566±0.038M⊕, and 0.086±0.084M⊕ for planets b, c, d, e, f, g, and h, respectively.

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Figure 4 indicates that – to within the errors of our determinations – the four most distant planets are consistent with pure water compositions, and in any event, are substantially less dense either Mars or Venus.
Post by: Bynaus on 04/18/2017 06:52 AM
Cross-posting from the 'NASA's Trappist-1 Announcement - Feb 22, 2017' thread.

Updated Masses for the TRAPPIST-1 Planets (arXiv) (https://arxiv.org/abs/1704.04290)

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The newly detected TRAPPIST-1 system, with seven low-mass, roughly Earth-sized planets transiting a nearby ultra-cool dwarf, is one of the most important exoplanet discoveries to date. The short baseline of the available discovery observations, however, means that the planetary masses (obtained through measurement of transit timing variations of the planets of the system) are not yet well constrained. The masses reported in the discovery paper were derived using a combination of photometric timing measurements obtained from the ground and from the Spitzer spacecraft, and have uncertainties ranging from 30\% to nearly 100\%, with the mass of the outermost, P=18.8d, planet h remaining unmeasured. Here, we present an analysis that supplements the timing measurements of the discovery paper with 73.6 days of photometry obtained by the K2 Mission. Our analysis refines the orbital parameters for all of the planets in the system. We substantially improve the upper bounds on eccentricity for inner six planets (finding e<0.02 for inner six known members of the system), and we derive masses of 0.79±0.27M⊕, 1.63±0.63M⊕, 0.33±0.15M⊕, 0.24+0.56−0.24M⊕, 0.36±0.12M⊕, 0.566±0.038M⊕, and 0.086±0.084M⊕ for planets b, c, d, e, f, g, and h, respectively.

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Figure 4 indicates that – to within the errors of our determinations – the four most distant planets are consistent with pure water compositions, and in any event, are substantially less dense either Mars or Venus.

Very interesting, the densities of the planets are now (in g/cm3):

b: 3.4 +- 1.2
c: 7.63 +- 3.02
d: 3.95 +- 1.86
e: <5.71
f: 1.74 +- 0.61
g: 2.18 +- 0.28
h: <2.54

It is quite remarkable that the density drops significantly below the 3-5 range (= Earth-like, rocky planets) for the planets with equilibrium temperatures below 0°C, the freezing point of water (at 1 bar, but its quite possible that these planets have ~1 bar atmospheres). This might suggest the outer planets f,g,h are essentially super-Ganymedes.
Post by: Star One on 04/19/2017 08:54 PM
Newly Discovered Exoplanet May be Best Candidate in Search for Signs of Life

Transiting rocky super-Earth found in habitable zone of quiet red dwarf star

An exoplanet orbiting a red dwarf star 40 light-years from Earth may be the new holder of the title “best place to look for signs of life beyond the Solar System”. Using ESO’s HARPS instrument at La Silla, and other telescopes around the world, an international team of astronomers discovered a “super-Earth” orbiting in the habitable zone around the faint star LHS 1140. This world is a little larger and much more massive than the Earth and has likely retained most of its atmosphere. This, along with the fact that it passes in front of its parent star as it orbits, makes it one of the most exciting future targets for atmospheric studies. The results will appear in the 20 April 2017 issue of the journal Nature.

The newly discovered super-Earth LHS 1140b orbits in the habitable zone around a faint red dwarf star, named LHS 1140, in the constellation of Cetus (The Sea Monster) [1]. Red dwarfs are much smaller and cooler than the Sun and, although LHS 1140b is ten times closer to its star than the Earth is to the Sun, it only receives about half as much sunlight from its star as the Earth and lies in the middle of the habitable zone. The orbit is seen almost edge-on from Earth and as the exoplanet passes in front of the star once per orbit it blocks a little of its light every 25 days.

“This is the most exciting exoplanet I’ve seen in the past decade,” said lead author Jason Dittmann of the Harvard-Smithsonian Center for Astrophysics (Cambridge, USA). “We could hardly hope for a better target to perform one of the biggest quests in science — searching for evidence of life beyond Earth.”

"The present conditions of the red dwarf are particularly favourable — LHS 1140 spins more slowly and emits less high-energy radiation than other similar low-mass stars," explains team member Nicola Astudillo-Defru from Geneva Observatory, Switzerland [2].

For life as we know it to exist, a planet must have liquid surface water and retain an atmosphere. When red dwarf stars are young, they are known to emit radiation that can be damaging for the atmospheres of the planets that orbit them. In this case, the planet's large size means that a magma ocean could have existed on its surface for millions of years. This seething ocean of lava could feed steam into the atmosphere long after the star has calmed to its current, steady glow, replenishing the planet with water.

The discovery was initially made with the MEarth facility, which detected the first telltale, characteristic dips in light as the exoplanet passed in front of the star. ESO’s HARPS instrument, the High Accuracy Radial velocity Planet Searcher, then made crucial follow-up observations which confirmed the presence of the super-Earth. HARPS also helped pin down the orbital period and allowed the exoplanet’s mass and density to be deduced [3].

The astronomers estimate the age of the planet to be at least five billion years. They also deduced that it has a diameter 1.4 times larger than the Earth — almost 18 000 kilometres. But with a mass around seven times greater than the Earth, and hence a much higher density, it implies that the exoplanet is probably made of rock with a dense iron core.

This super-Earth may be the best candidate yet for future observations to study and characterise its atmosphere, if one exists. Two of the European members of the team, Xavier Delfosse and Xavier Bonfils both at the CNRS and IPAG in Grenoble, France, conclude: “The LHS 1140 system might prove to be an even more important target for the future characterisation of planets in the habitable zone than Proxima b or TRAPPIST-1. This has been a remarkable year for exoplanet discoveries!” [4,5].

In particular, observations coming up soon with the NASA/ESA Hubble Space Telescope will be able to assess exactly how much high-energy radiation is showered upon LHS 1140b, so that its capacity to support life can be further constrained.

Further into the future — when new telescopes like ESO’s Extremely Large Telescope are operating — it is likely that we will be able to make detailed observations of the atmospheres of exoplanets, and LHS 1140b is an exceptional candidate for such studies.

http://www.eso.org/public/news/eso1712/?lang
Post by: Star One on 04/20/2017 08:58 PM
This is an excellent article on LHS 1140b including future plans for its study.

Newfound Super-Earth Boosts Search for Alien Life

Planet LHS 1140 b orbits a dim red dwarf star just 40 light-years away, making it a prime target for life-finding telescopes

https://www.scientificamerican.com/article/newfound-super-earth-boosts-search-for-alien-life/
Post by: Star One on 04/26/2017 06:52 PM
Speculations on Habitable Zone Waterworlds

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What to make of Fergus Simpson’s new paper on waterworlds, suggesting that most habitable zone planets are of this type? If such worlds are common, we may find that most planets in the habitable zones of their stars are capable of evolving life, but unlikely to host technological civilizations. An explanation for the so-called ‘Fermi Paradox’? Possibly, but there are all kinds of things that could account for our inability to see other civilizations, most of them covered by Stephen Webb in his If the Universe Is Teeming with Aliens … Where Is Everybody? (2nd ed., Springer 2015), which offers 75 solutions to the problem.

Simpson (University of Barcelona) makes his case in the pages of Monthly Notices of the Royal Astronomical Society, arguing that the balance maintained by a planetary surface with large amounts of both land and water is delicate. The author’s Bayesian statistical analysis suggests that most planets are dominated either by water or land, most likely water. Earth may, then, be something of an outlier, with most planets over 90 percent covered in water.

http://www.centauri-dreams.org/?p=37561
Post by: CuddlyRocket on 04/27/2017 01:53 AM
There seems to be a confusion in terminology prevalent. Is a waterworld a world covered in water, but which, like the Earth, is predominately made of rock and metal; or is a waterworld one which is predominately made of water (ice, actually)?

I think of a waterworld as being the latter, with the former described as an oceanworld. But I could be under a misapprehension! :)
Post by: Star One on 04/27/2017 08:47 AM
There seems to be a confusion in terminology prevalent. Is a waterworld a world covered in water, but which, like the Earth, is predominately made of rock and metal; or is a waterworld one which is predominately made of water (ice, actually)?

I think of a waterworld as being the latter, with the former described as an oceanworld. But I could be under a misapprehension! :)

I think of it as a watery Earth myself as that seemed to be what the article was referencing.
Post by: Star One on 04/27/2017 08:56 PM
Seems a decent summary.

New Planet Discoveries Signal a Shift in the Hunt for Alien Life

http://news.nationalgeographic.com/2017/04/new-planets-life-close-earth-space-science/
Post by: Star One on 04/28/2017 07:10 PM
Planetary Discovery around Ultracool Star

Quote
Small planets may be common around ultracool dwarfs, an idea that previous microlensing discoveries reinforce, along with the work on protoplanetary disks and the seven planets orbiting TRAPPIST-1. As to our expectations regarding planets in the galactic bulge as opposed to the disk, the jury is still out. The planets Spitzer has thus far found in its microlensing campaign for the galactic distribution of planets are all located in the disk. We have two upcoming Spitzer microlensing campaigns, one this year and one next, which should offer additional insights. The key question: Is the galactic bulge deficient in planets?

http://www.centauri-dreams.org/?p=37573

Here is the paper.

https://arxiv.org/abs/1703.08548
Post by: Star One on 05/03/2017 04:50 PM
Astronomers confirm nearby star a good model of our early solar system

http://www.news.iastate.edu/news/2017/05/02/eridani

http://www.centauri-dreams.org/?p=37606
Post by: Star One on 05/10/2017 08:46 PM
Exploring the Planet / Brown Dwarf Boundary

http://www.centauri-dreams.org/?p=37665
Post by: missinglink on 05/10/2017 09:10 PM
Poll:

If & when a future ultra-sensitive spectroscope detects chlorophyll in an exoplanet's atmosphere -- meaning ongoing photosynthesis by abundant plant life -- will NASA (plus maybe other government's space agencies) mount a hugely expensive effort (hundreds of billions of dollars) to send a robotic probe to that planet over a distance of, say, 20 lightyears? Knowing that radio transmission of results won't be received by anyone currently living? And with no guarantee of success?

Yes: Explore & investigate is in our genes, must find out if this is a Second Earth that can be our lifeboat & refuge

No: We will never leave solar system, age of discovery is over
Post by: gospacex on 05/10/2017 09:33 PM
Is it a trick question?

"(hundreds of billions of dollars) to send a robotic probe to that planet over a distance of, say, 20 lightyears" - well, such a probe could reach its destination somewhere in the year 50000, at best. Does not make sense, if you ask me...
Post by: Star One on 05/11/2017 06:20 AM
Is it a trick question?

"(hundreds of billions of dollars) to send a robotic probe to that planet over a distance of, say, 20 lightyears" - well, such a probe could reach its destination somewhere in the year 50000, at best. Does not make sense, if you ask me...
Answer invent a quicker way to get there obviously.
Post by: Torbjorn Larsson, OM on 05/11/2017 11:08 AM
Poll:

If & when a future ultra-sensitive spectroscope detects chlorophyll in an exoplanet's atmosphere -- meaning ongoing photosynthesis by abundant plant life -- will NASA (plus maybe other government's space agencies) mount a hugely expensive effort (hundreds of billions of dollars) to send a robotic probe to that planet over a distance of, say, 20 lightyears? Knowing that radio transmission of results won't be received by anyone currently living? And with no guarantee of success?

Yes: Explore & investigate is in our genes, must find out if this is a Second Earth that can be our lifeboat & refuge

No: We will never leave solar system, age of discovery is over

I'll echo that: Is it a trick question?

Some of the problems:
- Science & technology & societal development is not decided by polls.
- Finding biotic signatures is discovery. The (non)question is how fast this age of discovery will put up larger observatories to find out more. My guess: very quickly.

The lifeboat/refuge/faster probes perspective is Utopia fantasy, as far as I can see. [Admittedly: 1. I am tired of seeing such ideas around discussions containing a smidgen of science. The at odds juxtaposition is like scratching sounds from a window. But never mind that. 2. Something like Starshot may be feasible and complement other methods of discovery. Scaled up such can carry spores or even seeds, but not implant anything like our biosphere - such evolution will end up somewhere else in phylogenetic tree space. It would be a possible life refugia at best. But life is likely common, seeing how fast it emerged on Earth.]

Relativity physics puts a hard limit on economical expansion or 'refuge' (if not refugia) ideas. Whether or not individuals or even worlds would - like any parent - put aside resources for direct colonization is an open question.

[But I am reminded of the xkcd comic where Randall shows that on an exponential scale - the scale of economical growth - colonizing the Oort cloud is the largest effort after the Moon. From the Oort cloud the distance to the next cloud is nothing in relation. So if and when we colonize the resource full innards of Oort objects and put rocket engines on the outside - because orbiting is such a bounded life - I expect we will seed the galaxy. My guess: it will happen. But I do not see any connection with fears of extinction.]

Here is the crucial point as far as I can see: our species will go extinct. Nothing can or should stop that anymore than we can or should stop the death of individuals, assuming we want to continue evolving in order for the process of life to continue. The average lifetime of a mammal species is 1-2 Myrs, and we can see from H. erectus that the Homo lineage is, despite the bushy behavior, no exception. Even colonization won't stop that since speciation is an incipient process as soon as population interbreeding drops under an average of 1 breeding/generation. [A somewhat curious result from population genetics, the population sizes are divided out of the problem.]

Life on the other hand may never go extinct as long as it finds a habitable environment. Our one sample is roughly as old as the habitable environment on Earth, indicating a mature biosphere is hardy. I expect our soon-to-come - give or take a Myr - descendants will remember us fondly in the way we remember our great grandparents. "But they lived then, we live now."
Post by: missinglink on 05/11/2017 08:34 PM
Not a "trick question", just wanted to get an idea how NSF Forum members expect that the relevant organizations -- and the public, which funds them -- will react to detection of life on exoplanets.

Post by: dror on 05/11/2017 09:14 PM
My whole interest in space derives from the hope to see that picture.
Sadly, I don't think the reaction will be as immediate or effective as you have suggested. I do hope, though, that it will encourage more reasonable discussions, put some sense in some people who needs it, and allow for a general increase in funding for research.
We must remember, though, that while an exoplanet may save the human race, it will not save the humans on this planet, and won't save this planet from them.
Post by: Star One on 05/11/2017 09:19 PM
NASA Study Finds Unexpectedly Primitive Atmosphere Around ‘Warm Neptune’

Quote
A study combining observations from NASA’s Hubble and Spitzer space telescopes reveals that the distant planet HAT-P-26b has a primitive atmosphere composed almost entirely of hydrogen and helium. Located about 437 light years away, HAT-P-26b orbits a star roughly twice as old as the sun.

The analysis is one of the most detailed studies to date of a “warm Neptune,” or a planet that is Neptune-sized and close to its star. The researchers determined that HAT-P-26b’s atmosphere is relatively clear of clouds and has a strong water signature, although the planet is not a water world. This is the best measurement of water to date on an exoplanet of this size.

The discovery of an atmosphere with this composition on this exoplanet has implications for how scientists think about the birth and development of planetary systems. Compared to Neptune and Uranus, the planets in our solar system with about the same mass, HAT-P-26b likely formed either closer to its host star or later in the development of its planetary system, or both.

https://www.nasa.gov/feature/goddard/2017/nasa-study-finds-unexpectedly-primitive-atmosphere-around-warm-neptune
Post by: missinglink on 05/12/2017 02:54 PM
We must remember, though, that while an exoplanet may save the human race, it will not save the humans on this planet, and won't save this planet from them.
True, true...

Life on exoplanets may be detected sooner than we think, if this proposal comes to fruition: https://www.nasa.gov/directorates/spacetech/niac/2017_Phase_I_Phase_II/Solar_Gravity_Lens_Mission/

Just imagine, an habitable planet that doesn't need to be terraformed ... because it's already teeming with lush plant life. Send seed ships with human eggs and sperm, make of it a Second Earth. Ethical to do this to another biosphere? I guess not. Anyway, cost is prohibitive and First Earth gets no return on investment after bankrupting itself to stage the mission. So, probably never happen.
Post by: gospacex on 05/12/2017 05:50 PM
We must remember, though, that while an exoplanet may save the human race, it will not save the humans on this planet, and won't save this planet from them.
True, true...

Life on exoplanets may be detected sooner than we think, if this proposal comes to fruition: https://www.nasa.gov/directorates/spacetech/niac/2017_Phase_I_Phase_II/Solar_Gravity_Lens_Mission/

Travel to 550 AU to be able to observe a single target? Because steering this telescope would be... difficult, to say the least.

Quote
Just imagine, an habitable planet that doesn't need to be terraformed ... because it's already teeming with lush plant life. Send seed ships with human eggs and sperm, make of it a Second Earth. Ethical to do this to another biosphere? I guess not.

How about founding "bacteria have rights!" movement? It's sickening to think what massacres some people perpetrate daily, using only toothbrushes!
Post by: Oli on 05/14/2017 03:42 PM
We must remember, though, that while an exoplanet may save the human race, it will not save the humans on this planet, and won't save this planet from them.
True, true...

Life on exoplanets may be detected sooner than we think, if this proposal comes to fruition: https://www.nasa.gov/directorates/spacetech/niac/2017_Phase_I_Phase_II/Solar_Gravity_Lens_Mission/

Travel to 550 AU to be able to observe a single target? Because steering this telescope would be... difficult, to say the least.

If we find a planet with the right atmosphere (i.e. Earth-like), such a mission could certainly be worth it. I'm not aware of any other method that could deliver a 1000x1000px image of an exoplanet other than truly gigantic space telescopes.
Post by: TakeOff on 05/14/2017 06:45 PM
Just imagine, an habitable planet that doesn't need to be terraformed ... because it's already teeming with lush plant life. Send seed ships with human eggs and sperm, make of it a Second Earth. Ethical to do this to another biosphere? I guess not. Anyway, cost is prohibitive and First Earth gets no return on investment after bankrupting itself to stage the mission. So, probably never happen.

That would be unlikely. Even here on Earth we've had about today's oxygen level only 1/10 of the planet's history. And we might've problems with the microbiomes available before we evolved here. I think we are extremely tightly integrated with Earth as it is now and will have to construct our own environment in other places.
Post by: TakeOff on 05/14/2017 06:56 PM
Life on exoplanets may be detected sooner than we think, if this proposal comes to fruition: https://www.nasa.gov/directorates/spacetech/niac/2017_Phase_I_Phase_II/Solar_Gravity_Lens_Mission/

Travel to 550 AU to be able to observe a single target? Because steering this telescope would be... difficult, to say the least.
The LISA space laser interferometer is expected to perform an even greater miracle of precision flying. Solar gravity lensing is one of the "resources" that could be taken advantage of from early almost-interstellar flight. Other opportunities might be huge baseline parallax distance measurements and maybe radio interferometry, besides flying by distant objects and studying the interstellar medium. I think that a single object like an interesting exoplanet or the SMBH could be well worth a dedicated observatory.
Post by: hop on 05/14/2017 07:22 PM
The LISA space laser interferometer is expected to perform an even greater miracle of precision flying.
Precision distance measurement between active spacecraft is not equivalent to precision pointing, so it's a *different* miracle rather than a greater one. But of all the miracles required to make gravitational focus telescope work, pointing probably isn't the biggest.

If we find a planet with the right atmosphere (i.e. Earth-like), such a mission could certainly be worth it. I'm not aware of any other method that could deliver a 1000x1000px image of an exoplanet other than truly gigantic space telescopes.
It's not clear a gravitational focus telescope can actually do this in practice either. See https://arxiv.org/abs/1604.06351

Post by: CuddlyRocket on 05/16/2017 08:30 PM
K2-106, a system containing a metal rich planet and a planet of lower density (arXiv) (https://arxiv.org/pdf/1705.04163.pdf)

Quote
The two planets have similar masses, though very different densities. For K2-106b we derive Mp = 7.69 ± 0.82 M⊕, Rp = 1.52 ± 0.16 R⊕, and a high density of 12.0 +4.8 −3.2 g cm−3. For K2-106c, we find 6.79 ± 2.29 M⊕, Rp = 2.59 ± 0.27 R⊕ and a relatively low density of 2.4 +1.6 −1.1 g cm−3.

The 'Fulton Gap' has been proposed to be used to distinguish between 'super-Earths' and 'sub-Neptunes' - with the former having a radius of 1-1.75 R⊕ and the latter one of 1.75–3.5 R⊕. On that definition, this is an interesting system where the super-Earth is more massive than the sub-Neptune!
Post by: Star One on 05/16/2017 10:10 PM
New 'styrofoam' planet provides tools in search for habitable planets

https://m.phys.org/news/2017-05-styrofoam-planet-tools-habitable-planets.html
Post by: Star One on 05/25/2017 07:15 PM
Newly Found Exoplanet May Have Ring System Dwarfing Saturn’s

If confirmed, the  world’s rings would be some 200 times wider than Saturn’s and could reveal clues to our solar system’s early history

https://www.scientificamerican.com/article/newly-found-exoplanet-may-have-ring-system-dwarfing-saturn-rsquo-s/
Post by: Star One on 05/30/2017 11:28 AM
Astronomers discover 'super-Earth' planet orbiting nearby star

Quote
Abstract
We report the discovery of a super-Earth orbiting at the inner edge of the habitable zone of the star GJ 625 based on the analysis of the radial-velocity (RV) time series from the HARPS-N spectrograph, consisting in 151 HARPS-N measurements taken over 3.5 yr. GJ 625 b is a planet with a minimum mass M sin i of 2.82 ± 0.51 M⊕ with an orbital period of 14.628 ± 0.013 days at a distance of 0.078 AU of its parent star. The host star is the quiet M2 V star GJ 625, located at 6.5 pc from the Sun. We find the presence of a second radial velocity signal in the range 74-85 days that we relate to stellar rotation after analysing the time series of Ca II H&K and Hα spectroscopic indicators, the variations of the FWHM of the CCF and and the APT2 photometric light curves. We find no evidence linking the short period radial velocity signal to any activity proxy.

https://m.phys.org/news/2017-05-astronomers-super-earth-planet-orbiting-nearby.html
Post by: hop on 05/30/2017 09:57 PM
More fuel for the M-dwarf tidal locking debate:

On the Spin States of Habitable Zone Exoplanets Around M Dwarfs:The Effect of a Near-Resonant Companion (https://arxiv.org/abs/1705.09685) Alec M. Vinson, Brad M.S. Hansen

Quote
One longstanding problem for the potential habitability of planets within M dwarf systems is their likelihood to be tidally locked in a synchronously rotating spin state. This problem thus far has largely been addressed only by considering two objects: the star and the planet itself. However, many systems have been found to harbor multiple planets, with some in or very near to mean-motion resonances. The presence of a planetary companion near a mean-motion resonance can induce oscillatory variations in the mean-motion of the planet, which we demonstrate can have significant effects on the spin-state of an otherwise synchronously rotating planet. In particular, we find that a planetary companion near a mean-motion resonance can excite the spin states of planets in the habitable zone of small, cool stars, pushing otherwise synchronously rotating planets into higher amplitude librations of the spin state, or even complete circulation resulting in effective stellar days with full surface coverage on the order of years or decades. This increase in illuminated area can have potentially dramatic influences on climate, and thus on habitability. We also find that the resultant spin state can be very sensitive to initial conditions due to the chaotic nature of the spin state at early times within certain regimes. We apply our model to two hypothetical planetary systems inspired by the K00255 and TRAPPIST-1 systems, which both have Earth-sized planets in mean-motion resonances orbiting cool stars.
Post by: CuddlyRocket on 05/31/2017 12:30 AM
Astronomers discover 'super-Earth' planet orbiting nearby star

Quote
Abstract
We report the discovery of a super-Earth ... with a minimum mass M sin i of 2.82 ± 0.51 M⊕ ...

https://m.phys.org/news/2017-05-astronomers-super-earth-planet-orbiting-nearby.html

The authors have classified this as a super-Earth on the basis that its mass is between that of Earth and Neptune. I get the impression that most astronomers in the field would consider that definition to be overly-broad, with objects at the upper end of that mass range being referred to as mini-Neptunes instead. The authors do note that the term super-Earth "is also used by astronomers to describe planets bigger than Earth but smaller than the so-called "mini-Neptunes" (with a radius between two to four Earth-radii)."

Is there a confusion between definitions of super-Earths/mini-Neptunes based on mass and those based on the radius? Do astronomers using radial velocity techniques, which gives the mass, differ from their colleagues using transit techniques, which gives the radius?

If this object has the same average density as the Earth, its radius (x sin i) would be 1.41 times that of Earth, which is below the super-Earth/mini-Neptune boundary at 1.75 Earth radii based on the so-called 'Fulton Gap'. However, this is above the boundary based on the transition in the mass-radius relation identified by Chen and Kipping. A borderline case!
Post by: Star One on 06/02/2017 07:14 PM
Citizen scientists uncover a cold new world near sun

Quote
A new citizen-science tool released earlier this year to help astronomers pinpoint new worlds lurking in the outer reaches of our solar system has already led to a discovery: a brown dwarf a little more than 100 light years away from the Sun. Just six days after the launch of the Backyard Worlds: Planet 9 website in February, four different users alerted the science team to the curious object, whose presence has since been confirmed via an infrared telescope. Details were recently published in the Astrophysical Journal Letters.

Quote
"It's possible that there is a cold world closer than what we believe to be the closest star to the Sun," Faherty said. "Given enough time, I think our volunteers are going help to complete the map of our solar neighborhood."

https://phys.org/news/2017-06-citizen-scientists-uncover-cold-world.amp
Post by: Star One on 06/05/2017 04:16 PM
Meet KELT-9b, the Hottest Exoplanet Ever Discovered

The exoplanet’s host star blasts it with so much radiation that it will someday evaporate.

Quote
KELT-9b may just be the weirdest exoplanet astronomer Scott Gaudi has ever found. Gaudi, a researcher at The Ohio State University in Columbus, is the lead author of a paper published today in Nature describing the newly discovered hot, gassy exoplanet that is 3 times the size of Jupiter and located 650 light-years away from Earth.

The newly found exoplanet is tidally locked to its host star, meaning one side eternally faces a blast of radiant heat, Gaudi said. The 4300°C temperature of KELT-9b’s “dayside” is only about 1000°C cooler than the surface of our Sun.

If all of KELT-9b were this hot rather than just the dayside, it could be a star. But it still falls short of that classification because it doesn’t heat itself by means of hydrogen fusion. Instead, its heat comes from the intense radiation from its nearby host star, KELT-9.

https://eos.org/articles/meet-kelt-9b-the-hottest-exoplanet-ever-discovered

Weirdly it's in a polar orbit around its star.
Post by: Star One on 06/08/2017 07:19 PM
Relevant to any exoplanets in orbit around them.

Ultraviolet Insights into Red Dwarf Flares

https://www.centauri-dreams.org/?p=37914
Post by: Star One on 06/09/2017 04:51 PM
Planet Formation around TRAPPIST-1

https://www.centauri-dreams.org/?p=37917
Post by: CuddlyRocket on 06/13/2017 02:44 AM
Two new massive planets detected around the star HD 27894 (https://phys.org/news/2017-06-massive-planets-star-hd.html) (Phys.org article).
Three planets around HD 27894 (https://arxiv.org/pdf/1706.00509.pdf) (arXiv paper).

Quote
(Abstract)
Aims. Our new program with HARPS aims to detect mean motion resonant planetary systems around stars which were previously reported to have a single bona fide planet, often based only on sparse radial velocity data.
Methods. Archival and new HARPS radial velocities for the K2V star HD 27894 were combined and fitted with a three-planet self-consistent dynamical model. The best-fit orbit was tested for long-term stability.
Results. We find clear evidence that HD 27894 is hosting at least three massive planets. In addition to the already known Jovian planet with a period Pb ≈ 18 days we discover a Saturn-mass planet with Pc ≈ 36 days, likely in a 2:1 mean motion resonance with the first planet, and a cold massive planet (≈ 5.3 MJup) with a period Pd ≈ 5170 days on a moderately eccentric orbit (ed = 0.39).
Conclusions. HD 27894 is hosting a massive, eccentric giant planet orbiting around a tightly packed inner pair of massive planets likely involved in an asymmetric 2:1 mean motion resonance. HD 27894 may be an important milestone for probing planetary formation and evolution scenarios.
Post by: Star One on 06/13/2017 08:24 AM
I still can't help wonder if there are more planets in the large gap.
Post by: Bynaus on 06/13/2017 08:36 AM
Sounds like a 55 Cancri analogue system. A few gas giants on closely packed orbits, with a large, slightly eccentric jovian at ca. 5 AU. The resonance of the innermost two jovians at 55 Cnc is closer to 3:1, and there are more known planets in the 55 Cnc system (a hot super-Earth and a light-weight gas giant in the "gap"), but the similarities are striking (surprisingly, the authors do not mention that in their paper).
Post by: Star One on 06/13/2017 08:35 PM
New evidence that all stars are born in pairs

Quote
Did our sun have a twin when it was born 4.5 billion years ago?

Almost certainly yes — though not an identical twin. And so did every other sunlike star in the universe, according to a new analysis by a theoretical physicist from the University of California, Berkeley, and a radio astronomer from the Smithsonian Astrophysical Observatory at Harvard University.

Many stars have companions, including our nearest neighbor, Alpha Centauri, a triplet system. Astronomers have long sought an explanation. Are binary and triplet star systems born that way? Did one star capture another? Do binary stars sometimes split up and become single stars?

Astonomers have even searched for a companion to our sun, a star dubbed Nemesis because it was supposed to have kicked an asteroid into Earth’s orbit that collided with our planet and exterminated the dinosaurs. It has never been found.

The new assertion is based on a radio survey of a giant molecular cloud filled with recently formed stars in the constellation Perseus, and a mathematical model that can explain the Perseus observations only if all sunlike stars are born with a companion.

“We are saying, yes, there probably was a Nemesis, a long time ago,” said co-author Steven Stahler, a UC Berkeley research astronomer.

“We ran a series of statistical models to see if we could account for the relative populations of young single stars and binaries of all separations in the Perseus molecular cloud, and the only model that could reproduce the data was one in which all stars form initially as wide binaries. These systems then either shrink or break apart within a million years.”

http://news.berkeley.edu/2017/06/13/new-evidence-that-all-stars-are-born-in-pairs/
Post by: Star One on 06/14/2017 07:46 PM
Mistaken brown dwarf is actually two planets orbiting each other

Quote
Finding massive planets is nothing new these days. But finding them orbiting each other instead of orbiting a star is unprecedented. An object initially thought to be a single brown dwarf is actually a pair of giant worlds. It’s not yet clear how this binary system formed, but the discovery may help redefine the line between planets and brown dwarfs – failed stars with tens of times the mass of Jupiter.

This pair of planets is made up of two balls of gas the size of Jupiter but almost four times more massive, separated by some 600 million kilometres, and slowly circling each other once per century or so. The young couple only emits light at infrared wavelengths, with residual heat from their formation, just 10 million years ago.

Observations with the 10-metre Keck II telescope, by a team led by William Best of the University of Hawaii, uncovered the binary system, with the help of adaptive optics that correct for the blurring effects of Earth’s atmosphere.

https://www.newscientist.com/article/2134712-mistaken-brown-dwarf-is-actually-two-planets-orbiting-each-other
Post by: CuddlyRocket on 06/14/2017 11:51 PM
Quote
But are they really planets? Maybe not. In the past, the dividing line between planets and brown dwarfs was generally placed at 14 Jupiter masses, when nuclear fusion of deuterium in the object’s core sets in.

But Latham argues that the best way to distinguish between the two is not by their mass but by how they form: brown dwarfs result from collapsing clouds of gas and dust, while planets form out of a stellar disk.

I think a lot (most, probably) of astronomers who have an opinion would say that these are not planets because they don't orbit a star or stellar remnant. But they're probably not rogue planets either, because it seems unlikely they were ejected from a stellar system as a binary couple. The problem with Latham's suggestion would seem to be how do you tell the difference between a solo brown dwarf and a solo rogue planet? And is there a minimum size, or is every pebble a brown dwarf? (Though this may not matter in practice as it would probably be difficult to detect anything smaller than a gas giant.)
Post by: clongton on 06/16/2017 12:20 AM
... how do you tell the difference between a solo brown dwarf and a solo rogue planet?

I suspect that would be the core temperature. A brown dwarf would be quite a bit warmer than a rogue planet, even a rocky one with a molten core.
Post by: jebbo on 06/19/2017 09:37 AM
An announcement from the Pale Red Dot team is expected at 11am CET:

Almost certainly to do with their Barnard's Star campaign (which started a couple of months ago)

--- Tony
Post by: Alpha_Centauri on 06/19/2017 10:22 AM
Sounds like it is just announcing the search rather than any discoveries yet.
Post by: jebbo on 06/19/2017 10:40 AM
Yes.  Search started on June 15th. I got the impression from one of the team that they started looking at Barnard's Star earlier, but apparently not.

They will also be looking at Ross 154 (a flare star).  Home to "Glory Station" in Cherryh's Alliance/Union setting.

--- Tony
Post by: Star One on 06/19/2017 10:49 AM
Sounds like it is just announcing the search rather than any discoveries yet.

I was under the impression there has been an ongoing examination of Barnard's star?

Yes.  Search started on June 15th. I got the impression from one of the team that they started looking at Barnard's Star earlier, but apparently not.

They will also be looking at Ross 154 (a flare star).  Home to "Glory Station" in Cherryh's Alliance/Union setting.

--- Tony

Seems a bit pointless to prioritise a flare star in the search.
Post by: Alpha_Centauri on 06/19/2017 10:56 AM
Proxima is a flare star too, many M dwarfs are.  It's the occupational hazard.

Speaking of which they will also be observing Proxima again for further planets.  Data to be released in real-time.
Post by: jebbo on 06/19/2017 11:03 AM
Seems a bit pointless to prioritise a flare star in the search.

Why? The point of this is to find the nearest planets (i.e. that are the most susceptible to follow-up).

Flare stars (well all M dwarfs really) are a bit problematic for habitability, but - depending on the initial water fraction - it is not ruled out.

--- Tony
Post by: Star One on 06/19/2017 11:20 AM
Seems a bit pointless to prioritise a flare star in the search.

Why? The point of this is to find the nearest planets (i.e. that are the most susceptible to follow-up).

Flare stars (well all M dwarfs really) are a bit problematic for habitability, but - depending on the initial water fraction - it is not ruled out.

--- Tony

I assumed obviously mistakenly by the fact that the OP classed it as a flare star that they were indicating that even amongst M dwarfs it's was very active, otherwise why mention it?
Post by: jebbo on 06/19/2017 11:55 AM
I assumed obviously mistakenly by the fact that the OP classed it as a flare star that they were indicating that even amongst M dwarfs it's was very active, otherwise why mention it?

It is more active than most - it is a UV Ceti type star, with major flares every couple of days or so - which I thought worth mentioning, that's all.

Its age is thought to be <1Gyr so it is a fairly young star, but this age is poorly constrained (gyrochronology!), and M dwarfs become less active with age.

And from a different angle, looking at active flare stars will help us understand the effects of flares.

--- Tony
Post by: Star One on 06/19/2017 12:02 PM
As a general point are they going to try and tie down Proxima C which I believe is meant to be a larger planet further out than b?
Post by: jebbo on 06/19/2017 12:25 PM
As a general point are they going to try and tie down Proxima C which I believe is meant to be a larger planet further out than b?

The ESO presser talks about more than one terrestrial sized planet, and there is a linear trend in the Proxima b RV data, so it will help. But whether the campaign will be long enough to confirm a "c" and its period is another question

Edit: there are variations in the 200-300 days and ~40day periods as well. A post is forthcoming on their website.

--- Tony
Post by: Star One on 06/19/2017 08:34 PM
Article on the same.

Pale Red Dot: Campaign 2

https://www.centauri-dreams.org/?p=37964
Post by: CuddlyRocket on 06/20/2017 06:11 AM

NASA Releases Kepler Survey Catalog with Hundreds of New Planet Candidates
Here is the briefing material ... [and] the archived video of the press conference:

Quote
... precise measurements of thousands of planets, [reveals] two distinct groups of small planets ... a clean division in the sizes of rocky, Earth-size planets and gaseous planets smaller than Neptune. Few planets were found between those groupings. ...

“We like to think of this study as classifying planets in the same way that biologists identify new species of animals,” said Benjamin Fulton, doctoral candidate at the University of Hawaii in Manoa, and lead author of the second study. “Finding two distinct groups of exoplanets is like discovering mammals and lizards make up distinct branches of a family tree.”

It seems that nature commonly makes rocky planets up to about 75 percent bigger than Earth. For reasons scientists don't yet understand, about half of those planets take on a small amount of hydrogen and helium that dramatically swells their size, allowing them to "jump the gap" and join the population closer to Neptune’s size.

This is what is being called by some (not Benjamin - though he possibly doesn't object! :) ) the Fulton Gap. He gives an explanation in the video as to why it might arise.
Post by: jebbo on 06/20/2017 10:36 AM
This is what is being called by some (not Benjamin - though he possibly doesn't object! :) ) the Fulton Gap. He gives an explanation in the video as to why it might arise.

The original paper is here https://arxiv.org/abs/1703.10375 (https://arxiv.org/abs/1703.10375), and predates the latest DR25 release.

The gap is also known as the "photoevaporation desert" ;-)

--- Tony

Post by: Alpha_Centauri on 06/20/2017 11:16 AM
The photoevaporation desert and the Fulton gap are separate as far as I know. You can see this in the bottom diagram page 12. The photoevaporation desert is the noticeable lack of Neptunes in the very highest insolations, top left. The Fulton gap is the distinct relatively low occurrence gap marked by the crossing point between the two lines denoting the atmospheric loss and gas poor models (the point being the data did not rule out either cause).
Post by: jebbo on 06/20/2017 12:25 PM
You are quite right! I should have re-read the paper as I clearly misremembered it.  What I should have said was "photoevaporation valley", which has two competing theories on cause.

The joys of getting up at 5:30am with insufficient coffee :-)

--- Tony
Post by: Alpha_Centauri on 06/20/2017 12:52 PM
I would say you are forgiven, but then again no one is allowed to be wrong on the internet.  :P
Post by: Star One on 06/20/2017 07:03 PM
A New Classification Scheme for Kepler Planets

https://www.centauri-dreams.org/?p=37972

This seems to make an indirect case for planet nine being as that's meant to be our missing mini-Neptune.
Post by: Star One on 06/23/2017 08:52 PM
A Partly Cloudy Exoplanet

http://www.skyandtelescope.com/astronomy-news/a-partly-cloudy-exoplanet/
Post by: Star One on 06/27/2017 10:56 AM
Betelgeuse captured by ALMA

Quote
This orange blob shows the nearby star Betelgeuse, as seen by the Atacama Large Millimeter/submillimeter Array (ALMA). This is the first time that ALMA has ever observed the surface of a star and this first attempt has resulted in the highest-resolution image of Betelgeuse available.

Betelgeuse is one of the largest stars currently known — with a radius around 1400 times larger than the Sun’s in the millimeter continuum. About 600 light-years away in the constellation of Orion (The Hunter), the red supergiant burns brightly, causing it to have only a short life expectancy. The star is just about eight million years old, but is already on the verge of becoming a supernova. When that happens, the resulting explosion will be visible from Earth, even in broad daylight.

The star has been observed in many other wavelengths, particularly in the visible, infrared, and ultraviolet. Using ESO’s Very Large Telescope astronomers discovered a vast plume of gas almost as large as our Solar System. Astronomers have also found a gigantic bubble that boils away on Betelgeuse’s surface. These features help to explain how the star is shedding gas and dust at tremendous rates (eso0927, eso1121). In this picture, ALMA observes the hot gas of the lower chromosphere of Betelgeuse at sub-millimeter wavelengths — where localised increased temperatures explain why it is not symmetric. Scientifically, ALMA can help us to understand the extended atmospheres of these hot, blazing stars.
Post by: CuddlyRocket on 06/27/2017 10:23 PM
Betelgeuse captured by ALMA (link to ESO webpage, including images) (http://www.eso.org/public/unitedkingdom/images/potw1726a/)
Title: Re: Exoplanets And Stars Thread
Post by: Star One on 06/28/2017 09:47 AM
Groundbreaking discovery confirms existence of orbiting supermassive black holes

Quote
For the first time ever, astronomers at The University of New Mexico say they've been able to observe and measure the orbital motion between two supermassive black holes hundreds of millions of light years from Earth - a discovery more than a decade in the making.
UNM Department of Physics & Astronomy graduate student Karishma Bansal is the first-author on the paper, 'Constraining the Orbit of the Supermassive Black Hole Binary 0402+379', recently published in The Astrophysical Journal. She, along with UNM Professor Greg Taylor and colleagues at Stanford, the U.S. Naval Observatory and the Gemini Observatory, have been studying the interaction between these black holes for 12 years.
"For a long time, we've been looking into space to try and find a pair of these supermassive black holes orbiting as a result of two galaxies merging," said Taylor. "Even though we've theorized that this should be happening, nobody had ever seen it until now."
In early 2016, an international team of researchers, including a UNM alumnus, working on the LIGO project detected the existence of gravitational waves, confirming Albert Einstein's 100-year-old prediction and astonishing the scientific community. These gravitational waves were the result two stellar mass black holes (~30 solar mass) colliding in space within the Hubble time. Now, thanks to this latest research, scientists will be able to start to understand what leads up to the merger of supermassive black holes that creates ripples in the fabric of space-time and begin to learn more about the evolution of galaxies and the role these black holes play in it.
Using the Very Long Baseline Array (VLBA), a system made up of 10 radio telescopes across the U.S. and operated in Socorro, N.M., researchers have been able to observe several frequencies of radio signals emitted by these supermassive black holes (SMBH). Over time, astronomers have essentially been able to plot their trajectory and confirm them as a visual binary system. In other words, they've observed these black holes in orbit with one another.

Title: Re: Exoplanets And Stars Thread
Post by: Star One on 07/04/2017 04:12 PM
Probability of CME Impact on Exoplanets Orbiting M Dwarfs and Solar-Like Stars

Quote
Solar coronal mass ejections (CMEs) produce adverse space weather effects at Earth. Planets in the close habitable zone of magnetically active M dwarfs may experience more extreme space weather than at Earth, including frequent CME impacts leading to atmospheric erosion and leaving the surface exposed to extreme flare activity. Similar erosion may occur for hot Jupiters with close orbits around solar-like stars. We have developed a model, Forecasting a CME's Altered Trajectory (ForeCAT), which predicts a CME's deflection. We adapt ForeCAT to simulate CME deflections for the mid-type M dwarf V374 Peg and hot Jupiters with solar-type hosts. V374 Peg's strong magnetic fields can trap CMEs at the M dwarfs's Astrospheric Current Sheet, the location of the minimum in the background magnetic field. Solar-type CMEs behave similarly, but have much smaller deflections and do not get trapped at the Astrospheric Current Sheet. The probability of planetary impact decreases with increasing inclination of the planetary orbit with respect to the Astrospheric Current Sheet - 0.5 to 5 CME impacts per day for M dwarf exoplanets, 0.05 to 0.5 CME impacts per day for solar-type hot Jupiters. We determine the minimum planetary magnetic field necessary to shield a planet's atmosphere from the CME impacts. M dwarf exoplanets require values between tens and hundreds of Gauss. Hot Jupiters around a solar-type star, however, require a more reasonable <30 G. These values exceed the magnitude required to shield a planet from the stellar wind, suggesting CMEs may be the key driver of atmospheric losses.

https://arxiv.org/abs/1605.02683
Title: Re: Exoplanets And Stars Thread
Post by: Star One on 07/04/2017 07:24 PM
Isotope shift and search for metastable superheavy elements in astrophysical data

Quote
Spectral lines belonging to the short-lifetime heavy radioactive elements up to Es (Z=99) have been found in the spectra of the Przybylski's star. We suggest that these unstable elements may be decay products of a "magic" metastable nucleus belonging to the the island of stability where the nuclei have a magic number of neutrons N=184. The laboratory-produced nuclei have a significantly smaller number of neutrons. To identify spectra of the N=184 isotopes of these nuclei and their neutron-reach superheavy decay products in astrophysical data we calculate the isotope shift which should be added to the laboratory - measured wavelenghs. The results for the isotopic shifts in the strongest optical electromagnetic transitions in No, Lr, Nh, Fl,and Z=120 elements are presented.

https://arxiv.org/abs/1703.04250
Post by: Star One on 07/06/2017 07:41 PM
A cosmic barbecue: Researchers spot 60 new 'hot Jupiter' candidates

Title: Re: Exoplanets And Stars Thread
Post by: CuddlyRocket on 07/07/2017 05:40 AM
^^ Paper on arXiv (https://arxiv.org/abs/1706.06602)

Interesting new technique for finding exoplanets, relying on an increase in light flux from a stellar system due to the added light reflected from the exoplanets, rather than a decrease due to a transit. The authors note that their technique needs to be validated by corroboration using doppler measurements, but if it is then it could also be used on other databases of light flux.
Title: Re: Exoplanets And Stars Thread
Post by: Star One on 07/07/2017 06:59 AM
^^ Paper on arXiv (https://arxiv.org/abs/1706.06602)

Interesting new technique for finding exoplanets, relying on an increase in light flux from a stellar system due to the added light reflected from the exoplanets, rather than a decrease due to a transit. The authors note that their technique needs to be validated by corroboration using doppler measurements, but if it is then it could also be used on other databases of light flux.
Isn't that paper directly related to the finding of those 60 hot Jupiter candidates covered in the article I posted directly above your post?
Title: Re: Exoplanets And Stars Thread
Post by: Star One on 07/07/2017 03:50 PM
The low-mass content of the massive young star cluster RCW 38

Quote
RCW 38 is a deeply embedded young (~1 Myr), massive star cluster located at a distance of 1.7 kpc. Twice as dense as the Orion Nebula Cluster, orders of magnitude denser than other nearby star forming regions, and rich in massive stars, RCW 38 is an ideal place to look for potential differences in brown dwarf formation efficiency as a function of environment. We present deep, high resolution adaptive optics data of the central ~0.5x0.5 pc^2 obtained with NACO at the Very Large Telescope. Through comparison with evolutionary models we determine masses and extinction for ~480 candidate members, and derive the first Initial Mass Function (IMF) of the cluster extending into the substellar regime. Representing the IMF as a set of power laws in the form dN/dM~M^(-alpha), we derive the slope alpha = 1.60+-0.13 for the mass range 0.5 - 20 MSun which is shallower than the Salpeter slope, but in agreement with results in several other young massive clusters. At the low-mass side, we find alpha = 0.71+-0.11 for masses between 0.02 and 0.5 MSun, or alpha = 0.81+-0.08 for masses between 0.02 and 1 MSun. Our result is in agreement with the values found in other young star-forming regions, revealing no evidence that a combination of high stellar densities and the presence of numerous massive stars affect the formation efficiency of brown dwarfs and very-low mass stars. We estimate that the Milky Way galaxy contains between 25 and 100 billion brown dwarfs (with masses > 0.03 MSun).

https://arxiv.org/abs/1707.00277
Title: Re: Exoplanets And Stars Thread
Post by: CuddlyRocket on 07/09/2017 07:57 PM
^^ Paper on arXiv (https://arxiv.org/abs/1706.06602)

Interesting new technique for finding exoplanets, relying on an increase in light flux from a stellar system due to the added light reflected from the exoplanets, rather than a decrease due to a transit. The authors note that their technique needs to be validated by corroboration using doppler measurements, but if it is then it could also be used on other databases of light flux.
Isn't that paper directly related to the finding of those 60 hot Jupiter candidates covered in the article I posted directly above your post?

Yes. Hence the two up-arrows at the beginning of my post, which is forum-speak for 'refers to previous post'.
Title: Re: Exoplanets And Stars Thread
Post by: Star One on 07/09/2017 07:59 PM
^^ Paper on arXiv (https://arxiv.org/abs/1706.06602)

Interesting new technique for finding exoplanets, relying on an increase in light flux from a stellar system due to the added light reflected from the exoplanets, rather than a decrease due to a transit. The authors note that their technique needs to be validated by corroboration using doppler measurements, but if it is then it could also be used on other databases of light flux.
Isn't that paper directly related to the finding of those 60 hot Jupiter candidates covered in the article I posted directly above your post?

Yes. Hence the two up-arrows at the beginning of my post, which is forum-speak for 'refers to previous post'.

I missed those using Tapatalk hence the post. So sorry about that.
Title: Re: Exoplanets And Stars Thread
Post by: CuddlyRocket on 07/11/2017 04:59 AM
- 2 up-arrows :) -

No problem. I could've just quoted you or spelt things out - but I was being unnecessarily concise, or lazy, or some combination thereof!
Title: Re: Exoplanets And Stars Thread
Post by: Star One on 07/12/2017 09:04 AM
Hidden Stars May Make Planets Appear Smaller

Quote
In the search for planets similar to our own, an important point of comparison is the planet's density. A low density tells scientists a planet is more likely to be gaseous like Jupiter, and a high density is associated with rocky planets like Earth. But a new study suggests some are less dense than previously thought because of a second, hidden star in their systems.

As telescopes stare at particular patches of sky, they can't always differentiate between one star and two. A system of two closely orbiting stars may appear in images as a single point of light, even from sophisticated observatories such as NASA's Kepler space telescope. This can have significant consequences for determining the sizes of planets that orbit just one of these stars, says a forthcoming study in the Astronomical Journal by Elise Furlan of Caltech/IPAC-NExScI in Pasadena, California, and Steve Howell at NASA's Ames Research Center in California's Silicon Valley.

"Our understanding of how many planets are small like Earth, and how many are big like Jupiter, may change as we gain more information about the stars they orbit," Furlan said. "You really have to know the star well to get a good handle on the properties of its planets."

Some of the most well-studied planets outside our solar system -- or exoplanets -- are known to orbit lone stars. We know Kepler-186f, an Earth-size planet in the habitable zone of its star, orbits a star that has no companion (the habitable zone is the distance at which a rocky planet could support liquid water on its surface). TRAPPIST-1, the ultra-cool dwarf star that is home to seven Earth-size planets, does not have a companion either. That means there is no second star complicating the estimation of the planets' diameters, and therefore their densities.

But other stars have a nearby companion, high-resolution imaging has recently revealed. David Ciardi, chief scientist at the NASA Exoplanet Science Institute (NExScI) at Caltech, led a large-scale effort to follow up on stars that Kepler had studied using a variety of ground-based telescopes. This, combined with other research, has confirmed that many of the stars where Kepler found planets have binary companions. In some cases, the diameters of the planets orbiting these stars were calculated without taking the companion star into consideration. That means estimates for their sizes should be smaller, and their densities higher, than their true values.

Previous studies determined that roughly half of all the sun-like stars in our sun's neighborhood have a companion within 10,000 astronomical units (an astronomical unit is equal to the average distance between the sun and Earth, 93 million miles or 150 million kilometers). Based on this, about 15 percent of stars in the Kepler field could have a bright, close companion -- meaning planets around these stars may be less dense than previously thought.

The Transit Problem for Binaries

When a telescope spots a planet crossing in front of its star -- an event called a "transit" -- astronomers measure the resulting apparent decrease in the star's brightness. The amount of light blocked during a transit depends on the size of the planet -- the bigger the planet, the more light it blocks, and the greater the dimming that is observed. Scientists use this information to determine the radius -- half the diameter -- of the planet.

If there are two stars in the system, the telescope measures the combined light of both stars. But a planet orbiting one of these stars will cause just one of them to dim. So, if you don't know that there is a second star, you will underestimate the size of the planet.

For example, if a telescope observes that a star dims by 5 percent, scientists would determine the transiting planet's size relative to that one star. But if a second star adds its light, the planet must be larger to cause the same amount of dimming.

If the planet orbits the brighter star in a binary pair, most of the light in the system comes from that star anyway, so the second star won't have a big effect on the planet's calculated size. But if the planet orbits the fainter star, the larger, primary star contributes more light to the system, and the correction to the calculated planet radius can be large -- it could double, triple or increase even more. This will affect how the planet's orbital distance is calculated, which could impact whether the planet is found to be in the habitable zone.

If the stars are roughly equal in brightness, the "new" radius of the planet is about 40 percent larger than if the light were assumed to come from a single star. Because density is calculated using the cube of the radius, this would mean a nearly three-fold decrease in density. The impact of this correction is most significant for smaller planets because it means a planet that had once been considered rocky could, in fact, be gaseous.

The New Study

In the new study, Furlan and Howell focused on 50 planets in the Kepler observatory's field of view whose masses and radii were previously estimated. These planets all orbit stars that have stellar companions within about 1,700 astronomical units. For 43 of the 50 planets, previous reports of their sizes did not take into account the contribution of light from a second star. That means a revision to their reported sizes is necessary.

In most cases, the change to the planets' reported sizes would be small. Previous research showed that 24 of the 50 planets orbit the bigger, brighter star in a binary pair. Moreover, Furlan and Howell determined that 11 of these planets would be too large to be planets if they orbited the fainter companion star. So, for 35 of the 50 planets, the published sizes will not change substantially.

But for 15 of the planets, they could not determine whether they orbit the fainter or the brighter star in a binary pair. For five of the 15 planets, the stars in question are of roughly equal brightness, so their densities will decrease substantially regardless of which star they orbit.

This effect of companion stars is important for scientists characterizing planets discovered by Kepler, which has found thousands of exoplanets. It will also be significant for NASA's upcoming Transiting Exoplanet Survey Satellite (TESS) mission, which will look for small planets around nearby, bright stars and small, cool stars.

"In further studies, we want to make sure we are observing the type and size of planet we believe we are," Howell said. "Correct planet sizes and densities are critical for future observations of high-value planets by NASA's James Webb Space Telescope. In the big picture, knowing which planets are small and rocky will help us understand how likely we are to find planets the size of our own elsewhere in the galaxy."

https://exoplanets.nasa.gov

https://www.jpl.nasa.gov/news/news.php?release=2017-187&rn=news.xml&rst=6893
Post by: Star One on 07/12/2017 01:17 PM
Eight planetary systems found hosting 20 super-Earth & Neptune-mass companions

Quote
A new treasure trove of planets, ranging from worlds with small masses and short orbital periods of less than 15 days to super-Earth-sized planets that can take up to a year to orbit their star, has been discovered by astronomers using the world’s most successful ground-based planet-finding instrument.

The 20 new worlds have been found around eight bright, Sun-like stars by the HARPS (High Accuracy Radial velocity Planet Searcher) Echelle Spectograph instrument, mounted on the 3.6m telescope at the European Southern Observatory in Chile. HARPS, which has discovered around 200 planets since 2003, is are able to measure the velocity of a star’s wobble incurred by the gravity of orbiting planets with the extreme precision of 1 m/s.

Quote
One of the systems observed was a binary system containing the stars HD 20781 and HD 20782. Although planets have been found in binary systems before, it is still uncertain how disruptive the gravitational tides from two stars can be to planet formation, or whether there could be long-term interactions between the two stars and their planets which make them unstable.

This system, however, is packed with planets. Orbiting around the star HD 201781 are two super-Earths with orbits of 5.3 and 13.9 days and two Neptune-mass planets with orbits of 29 and 86 days. The brighter star of the two, HD 20782, also has a Jupiter-sized world in an eccentric 595-day orbit.

Jason Dittman an astronomer at Harvard University was excited by the planets in the study and, in particular, this binary system. “These planets are really interesting because they have these longer orbital periods, and they complement the planets from transit surveys like Kepler. If we want a complete picture of what sort of planets exist in the universe, then discoveries like these are vital to the story,” he says.

Quote
Dittman believes that HARPS and other radial velocity surveys in general don’t get enough credit for the amount of time and dedication that goes into their observations.“Detecting planets with periods that are several years long takes a long time to do because you want to see the planet go around the star a couple of times.”

He continued, “The dedication and forward-thinking to get data on a star for many years is amazing. It’s great to see these long-running radial velocity programs continue to hit pay-dirt and find some longer period, eccentric systems with which to test our theories.”

https://astronomynow.com/2017/07/12/eight-planetary-systems-found-hosting-20-super-earth-neptune-mass-companions/
Title: Re: Exoplanets And Stars Thread
Post by: Star One on 07/12/2017 07:25 PM
Smallest-ever star discovered by astronomers

Quote
The smallest star yet measured has been discovered by a team of astronomers led by the University of Cambridge. With a size just a sliver larger than that of Saturn, the gravitational pull at its stellar surface is about 300 times stronger than what humans feel on Earth.

The star is likely as small as stars can possibly become, as it has just enough mass to enable the fusion of hydrogen nuclei into helium. If it were any smaller, the pressure at the centre of the star would no longer be sufficient to enable this process to take place. Hydrogen fusion is also what powers the Sun, and scientists are attempting to replicate it as a powerful energy source here on Earth.

These very small and dim stars are also the best possible candidates for detecting Earth-sized planets which can have liquid water on their surfaces, such as TRAPPIST-1, an ultracool dwarf surrounded by seven temperate Earth-sized worlds.

The newly-measured star, called EBLM J0555-57Ab, is located about 600 light-years away. It is part of a binary system, and was identified as it passed in front of its much larger companion, a method which is usually used to detect planets, not stars. Details will be published in the journal Astronomy & Astrophysics.

“Our discovery reveals how small stars can be,” said Alexander Boetticher, the lead author of the study, and a Master’s student at Cambridge’s Cavendish Laboratory and Institute of Astronomy. “Had this star formed with only a slightly lower mass, the fusion reaction of hydrogen in its core could not be sustained, and the star would instead have transformed into a brown dwarf.”

https://astronomynow.com/2017/07/12/smallest-ever-star-discovered-by-astronomers/
Title: Re: Exoplanets And Stars Thread
Post by: Star One on 07/13/2017 07:20 PM
More to Life Than the Habitable Zone

Quote
The teams, both led by researchers at the Harvard-Smithsonian Center for Astrophysics (CfA) in Cambridge, Mass., say the behavior of the star in the TRAPPIST-1 system makes it much less likely than generally thought, that planets there could support life.

The TRAPPIST-1 star, a red dwarf, is much fainter and less massive than the Sun. It is rapidly spinning and generates energetic flares of ultraviolet (UV) radiation.

The first team, a pair of CfA theorists, considered many factors that could affect conditions on the surfaces of planets orbiting red dwarfs. For the TRAPPIST-1 system they looked at how temperature could have an impact on ecology and evolution, plus whether ultraviolet radiation from the central star might erode atmospheres around the seven planets surrounding it. These planets are all much closer to the star than the Earth is to the Sun, and three of them are located well within the habitable zone.

"The concept of a habitable zone is based on planets being in orbits where liquid water could exist," said Manasvi Lingam, a Harvard researcher who led the study. "This is only one factor, however, in determining whether a planet is hospitable for life."

Lingam and his co-author, Harvard professor Avi Loeb, found that planets in the TRAPPIST-1 system would be barraged by UV radiation with an intensity far greater than experienced by Earth.

"Because of the onslaught by the star's radiation, our results suggest the atmosphere on planets in the TRAPPIST-1 system would largely be destroyed," said Loeb. "This would hurt the chances of life forming or persisting."

Lingam and Loeb estimate that the chance of complex life existing on any of the three TRAPPIST-1 planets in the habitable zone is less than 1% of that for life existing on Earth.

In a separate study, another research team from the CfA and the University of Massachusetts in Lowell found that the star in TRAPPIST-1 poses another threat to life on planets surrounding it. Like the Sun, the red dwarf in TRAPPIST-1 is sending a stream of particles outwards into space. However, the pressure applied by the wind from TRAPPIST-1's star on its planets is 1,000 to 100,000 times greater than what the solar wind exerts on the Earth.

The authors argue that the star’s magnetic field will connect to the magnetic fields of any planets in orbit around it, allowing particles from the star’s wind to directly flow onto the planet’s atmosphere. If this flow of particles is strong enough, it could strip the planet's atmosphere and perhaps evaporate it entirely.

https://www.cfa.harvard.edu/news/2017-20
Title: Re: Exoplanets And Stars Thread
Post by: Star One on 07/18/2017 07:40 PM
Why We Need a New Type of SETI Instrument

Quote
The SETI Institute has developed an instrument that, at relatively low cost, could continuously survey the entire night sky for brief laser pulses.  This is completely unlike the optical SETI efforts that have been made in the past, and continue to be made today: experiments that use sensitive photomultiplier detectors, but are limited to one star system at a time.  That’s akin to a radio SETI search able to only monitor a single frequency channel.  Extremely limited.

However, the Institute’s new Laser SETI instrument is not constrained in this way – it can look everywhere simultaneously.  The technology has been prototyped and subjected to preliminary tests, and consists of a robust assembly of straightforward optical and mechanical components.  It can be easily and inexpensively) replicated.

http://www.seti.org/why-we-need-a-new-type-of-seti-instrument
Title: Re: Exoplanets And Stars Thread
Post by: Star One on 07/19/2017 07:04 PM
“Variable and polarized radio emission from the T6 brown dwarf WISEP J112254.73+255021.5”

Quote
But we do see a lot of complicated variability in the radio emission! What I found to be the most exciting was the measurement shown in the lowest panel of the figure above. It shows the level of circular polarization of the radio waves we get from WISE 1122+25. Almost all astronomical objects emit light that is unpolarized in the circular sense — that is, 0% circular polarization. Radio-emitting brown dwarfs are among the rare objects that can produce high levels of circular polarization. The way we quantify things, circular polarization levels can range between +100%, meaning fully right-handed circular polarization, to –100%, for fully left-handed circular polarization.

What’s neat about the VLA data is that the polarization fraction seems to swing back and forth between the two states. We’ve seen brown dwarfs emit radio bursts with both kinds of handedness, but I’m not aware of any data showing these kind of long-lasting, abrupt transitions. And if you get a bit ambitious in the interpretation, you can imagine that maybe this handedness flips back periodically with the rotation of the brown dwarf. Looking at the different pieces of data, we found some evidence for periodicity at 116 minutes. But the whole observation only spanned 162 minutes, so that’s a very tentative idea — you’d want to see multiple flips back and forth all in sequence to be more confident.

But … if you want to get even more ambitious … You might be able to explain that kind of behavior if this object has a magnetic field that has a major axis that’s very misaligned with the rotation axis. With the right viewing geometry and magnetic polar caps that emitted strongly polarized radiation, you can get curves that look similar to the data.

Post by: Star One on 07/19/2017 07:53 PM
Astronomers discover Earth-sized exoplanet with very short orbital period

Quote
An international team of astronomers has detected a new Earth-sized exoplanet in an ultra-short period around its parent star. The alien world, designated EPIC 228813918 b, circles its host every four hours and 20 minutes, which makes it the second-shortest orbital period of a planet known to date. The finding was presented in a paper published July 14 on arXiv.org.

Quote
The newly found planet is slightly smaller than Earth (0.89 Earth radii). However, it's extremely massive – its estimated maximum mass is 0.7 Jupiter masses. The exoplanet orbits an M-dwarf star nearly half the size and mass of our sun every 4.3 hours. The planetary system is located some 310 light years away from the Earth.

Quote
The researchers also managed to determine the chemical composition of EPIC 228813918 b. According to them, the planet has an iron core and a silicate mantle. The minimum iron mass fraction was found to be about 0.52, which is greater than that of Earth, Venus or Mars, but smaller than that of Mercury.

https://phys.org/news/2017-07-astronomers-earth-sized-exoplanet-short-orbital.amp
Title: Re: Exoplanets And Stars Thread
Post by: Bynaus on 07/19/2017 08:26 PM
Quote
However, it's extremely massive – its estimated maximum mass is 0.7 Jupiter masses.

Complete BS (sorry). This is its 3-sigma upper limit mass, based on a full 5 data points... The authors use this figure only to show that the object is in the planetary mass regime (and is not, e.g., a white dwarf). Certainly, one cannot say from that observation alone that "its extremely massive".

Interestingly, they do calculate a minimum density for the planet (>6.4 g/cm3), which is given by the requirement that it orbits its star outside the Roche limit, and from this a minimum iron core fraction of 0.45 (higher than the Earth but lower than Mercury - but again, remember this is a lower limit).
Title: Re: Exoplanets And Stars Thread
Post by: as58 on 07/19/2017 09:12 PM
Complete BS (sorry). This is its 3-sigma upper limit mass, based on a full 5 data points... The authors use this figure only to show that the object is in the planetary mass regime (and is not, e.g., a white dwarf). Certainly, one cannot say from that observation alone that "its extremely massive".

That's some impressive misreporting by phys.org. The mass limit is not mentioned in the abstract, so they must've read the paper. Alas, apparently without understanding much.

edit: Some nitpicking, mass upper limit is based only on the two Keck/HIRES observations, which are much more accurate than Subaru/IRCS radial velocities.
Title: Re: Exoplanets And Stars Thread
Post by: CuddlyRocket on 07/20/2017 03:20 AM
Astronomers discover Earth-sized exoplanet with very short orbital period

From the arXiv paper (https://arxiv.org/abs/1707.04549):

Quote
For a stellar radius of 0.44 R and a radius ratio of ≈ 0.02, we derive a planetary radius of around 1.0 R⊕. For such a planet, we consider a very conservative upper-limit to the mass to be 3 M⊕ (Seager et al. 2007 predict a mass of around 2.7 M⊕ for a 1 R⊕ planet composed of solid iron).
Title: Re: Exoplanets And Stars Thread
Post by: Star One on 07/26/2017 06:33 PM
Gamma-ray burst captured in unprecedented detail

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Data from multiple telescopes used to address long-standing questions about the universe's most powerful explosions

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Gamma-ray bursts are among the most energetic and explosive events in the universe. They are also short-lived, lasting from a few milliseconds to about a minute. This has made it tough for astronomers to observe a gamma-ray burst in detail. Using a wide array of ground- and space-based telescope observations, astronomers constructed one of the most detailed descriptions of a gamma-ray burst to date.

https://www.sciencedaily.com/releases/2017/07/170726132110.htm
Title: Re: Exoplanets And Stars Thread
Post by: hop on 07/26/2017 07:46 PM
Oops. It seems some "validated" planets are more valid than others
Disproval of the validated planets K2-78b, K2-82b, and K2-92b (https://arxiv.org/abs/1707.08007) (accepted for publication in A&A)
Quote
Transiting super-Earths orbiting bright stars in short orbital periods are interesting targets for the study of planetary atmospheres. While selecting super-Earths suitable for further characterization from the ground among a list of confirmed and validated exoplanets detected by K2, we found some suspicious cases that led to us re-assessing the nature of the detected transiting signal. We did a photometric analysis of the K2 light curves and centroid motions of the photometric barycenters. Our study shows that the validated planets K2-78b, K2-82b, and K2-92b are actually not planets but background eclipsing binaries. The eclipsing binaries are inside the Kepler photometric aperture, but outside the ground-based high resolution images used for validation. We advise extreme care on the validation of candidate planets discovered by space missions. It is important that all the assumptions in the validation process are carefully checked. An independent confirmation is mandatory in order to avoid wasting valuable resources on further characterization of non-existent targets.
Post by: Star One on 07/26/2017 09:02 PM
Oops. It seems some "validated" planets are more valid than others
Disproval of the validated planets K2-78b, K2-82b, and K2-92b (https://arxiv.org/abs/1707.08007) (accepted for publication in A&A)
Quote
Transiting super-Earths orbiting bright stars in short orbital periods are interesting targets for the study of planetary atmospheres. While selecting super-Earths suitable for further characterization from the ground among a list of confirmed and validated exoplanets detected by K2, we found some suspicious cases that led to us re-assessing the nature of the detected transiting signal. We did a photometric analysis of the K2 light curves and centroid motions of the photometric barycenters. Our study shows that the validated planets K2-78b, K2-82b, and K2-92b are actually not planets but background eclipsing binaries. The eclipsing binaries are inside the Kepler photometric aperture, but outside the ground-based high resolution images used for validation. We advise extreme care on the validation of candidate planets discovered by space missions. It is important that all the assumptions in the validation process are carefully checked. An independent confirmation is mandatory in order to avoid wasting valuable resources on further characterization of non-existent targets.

Isn't this paper rather stating the obvious and the last Kepler main mission release was done off the back of follow up ground observations.
Title: Re: Exoplanets And Stars Thread
Post by: hop on 07/27/2017 03:13 AM
Isn't this paper rather stating the obvious and the last Kepler main mission release was done off the back of follow up ground observations.
No. Relevant sentence from the abstract
Quote
The eclipsing binaries are inside the Kepler photometric aperture, but outside the ground-based high resolution images used for validation.
In other words, there was strong evidence of the EBs in the Kepler data, but the team that "validated" the planets didn't do the checks that would have caught them, and also didn't detect the EBs in their ground based follow up because they were outside the FOV.

From the discussion
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Our result shows that, though planet validation techniques are useful tools, great care needs to be taken to correctly validate candidate planets discovered by space missions. Crossfield et al. (2016) made a sound statistical study and a careful and detailed ground-based characterization of the targets, including high angular resolution imaging, but they failed to look for possible contaminants a few arcseconds away from the targets. In the cases mentioned above, the contaminants were too far away to be included in the field of view of the high resolution image and they were not considered further in the analysis.  The reliability of a statistical study is only as good as the understanding of the contamination sources. Here we show i) that validation methods applied to these targets by Crossfield et al.  (2016) underestimate the impact of background contaminants and consequently, ii) the planet likelihood estimates are not representative of the true nature of the candidates in these cases.

We insist that this is not the result of a failure of the design of the validation procedure, but the result of an incorrect assessment of the impact on the photometry of neighbouring sources. Our results can be used to improve the performance of planet validation techniques.
(emphasis in the original)

FWIW, the original paper reporting these ex-planets is https://arxiv.org/abs/1607.05263
Title: Re: Exoplanets And Stars Thread
Post by: Alpha_Centauri on 07/27/2017 03:45 AM
Super-Pandora? Candidate Neptune-sized exomoon potentially orbiting Superjovian Kepler-1625b.

HEK VI: On the Dearth of Galilean Analogs in Kepler and the Exomoon Candidate Kepler-1625b I
https://arxiv.org/pdf/1707.08563.pdf
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Finally, we have briefly highlighted our identification of an exomoon candidate in the Kepler-1625 system, for which we have secured a follow-up observation with HST. This candidate has passed a thorough preliminary inspection, but we emphasize again our position that the Kepler data are insufficient to make a conclusive statement about the existence of this moon. Only after the HST observation is made [October 2017] should any claim about this moon’s existence be given much credence.
Title: Re: Exoplanets And Stars Thread
Post by: Star One on 07/27/2017 07:09 AM
So what do they want them to do go through all the data from Kepler again, that will take years and no doubt cost a fair bit of money?
Title: Re: Exoplanets And Stars Thread
Post by: Bynaus on 07/27/2017 07:49 AM
So what do they want them to do go through all the data from Kepler again, that will take years and no doubt cost a fair bit of money?

Who is they and them? The Kepler data are freely available.

Regarding the "super-Pandora", this is an exiting - potential - find. Such systems might be rare (just as Hot Jupiters turned out to be rare), but it would be no surprise that the first exomoon was indeed a somewhat exotic Jovian/Neptunian binary. Looking forward to the results coming from the upcoming HST observation.
Post by: Star One on 07/27/2017 08:12 AM
So what do they want them to do go through all the data from Kepler again, that will take years and no doubt cost a fair bit of money?

Who is they and them? The Kepler data are freely available.

Regarding the "super-Pandora", this is an exiting - potential - find. Such systems might be rare (just as Hot Jupiters turned out to be rare), but it would be no surprise that the first exomoon was indeed a somewhat exotic Jovian/Neptunian binary. Looking forward to the results coming from the upcoming HST observation.

The Kepler team, I assumed it would be obvious that's who I was referring to? After all how many groups are going to have the time and money to go through all that public data, money doesn't grow on trees these days.
Title: Re: Exoplanets And Stars Thread
Post by: Bynaus on 07/27/2017 11:20 AM
So what do they want them to do go through all the data from Kepler again, that will take years and no doubt cost a fair bit of money?

Who is they and them? The Kepler data are freely available.

Regarding the "super-Pandora", this is an exiting - potential - find. Such systems might be rare (just as Hot Jupiters turned out to be rare), but it would be no surprise that the first exomoon was indeed a somewhat exotic Jovian/Neptunian binary. Looking forward to the results coming from the upcoming HST observation.

The Kepler team, I assumed it would be obvious that's who I was referring to? After all how many groups are going to have the time and money to go through all that public data, money doesn't grow on trees these days.

There is no expectation towards the core Kepler team involved here. Its also not like there is a "final word" on the Kepler data, either. Different researchers have been looking at the same data for many years now and the way these data have been reduced (how we go from raw data to exoplanet parameters) has been improved time and again, and will no doubt continue to happen in the future to some extent.

Looking for exomoons is also a completely different thing - and thus requires a different approach and data processing pipline (see the linked paper) - than to look for exoplanets. The funding for this kind of projects using publicly available data depends on the funding background of the individual researcher. In this case, Kipping is both a tenured professor at a university and probably has some external project funding from NSF, NASA or other sources.
Title: Re: Exoplanets And Stars Thread
Post by: Star One on 07/27/2017 11:28 AM
So what do they want them to do go through all the data from Kepler again, that will take years and no doubt cost a fair bit of money?

Who is they and them? The Kepler data are freely available.

Regarding the "super-Pandora", this is an exiting - potential - find. Such systems might be rare (just as Hot Jupiters turned out to be rare), but it would be no surprise that the first exomoon was indeed a somewhat exotic Jovian/Neptunian binary. Looking forward to the results coming from the upcoming HST observation.

The Kepler team, I assumed it would be obvious that's who I was referring to? After all how many groups are going to have the time and money to go through all that public data, money doesn't grow on trees these days.

There is no expectation towards the core Kepler team involved here. Its also not like there is a "final word" on the Kepler data, either. Different researchers have been looking at the same data for many years now and the way these data have been reduced (how we go from raw data to exoplanet parameters) has been improved time and again, and will no doubt continue to happen in the future to some extent.

Looking for exomoons is also a completely different thing - and thus requires a different approach and data processing pipline (see the linked paper) - than to look for exoplanets. The funding for this kind of projects using publicly available data depends on the funding background of the individual researcher. In this case, Kipping is both a tenured professor at a university and probably has some external project funding from NSF, NASA or other sources.

The only way I can see any group reanalysing all the Kepler data is if someone comes up with an algorithm to do all the heavy lifting.
Title: Re: Exoplanets And Stars Thread
Post by: Alpha_Centauri on 07/27/2017 11:31 AM
Lead author on the exomoon paper explains their rationale for publishing now;

https://blogs.scientificamerican.com/observations/are-astronomers-on-the-verge-of-finding-an-exomoon/
Title: Re: Exoplanets And Stars Thread
Post by: LouScheffer on 07/27/2017 01:53 PM
Oops. It seems some "validated" planets are more valid than others
Disproval of the validated planets K2-78b, K2-82b, and K2-92b (https://arxiv.org/abs/1707.08007) (accepted for publication in A&A)
Quote
[...] Our study shows that the validated planets K2-78b, K2-82b, and K2-92b are actually not planets but background eclipsing binaries. The eclipsing binaries are inside the Kepler photometric aperture, but outside the ground-based high resolution images used for validation. We advise extreme care on the validation of candidate planets discovered by space missions. It is important that all the assumptions in the validation process are carefully checked. An independent confirmation is mandatory in order to avoid wasting valuable resources on further characterization of non-existent targets.

OK, they found that 3 out of 104 were really false positives, where only one was expected (statistically), then figured out why so it can be avoided in the future.  Clearly valuable, but it does not change the overall exo-planet statistics much.  If you are trying to do any sort of planetary census, there are much bigger sources of error.  If you are zooming in on one particular star, though, it's worth double checking.
Title: Re: Exoplanets And Stars Thread
Post by: Star One on 07/27/2017 04:15 PM
Posting this mostly because of the seemingly bizarre attitude of the IAU to the naming of this comet, which has resulted in the team who discovered it not being credited.

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Never heard of ASAS-SN? It’s an automated sky survey hunting for supernovae in both hemispheres, with instruments based at Haleakala in Hawaii and Cerro Tololo in Chile. Though the survey targets supernovae, it does on occasion pick up other interesting astronomical phenomena as well. This is the first comet discovery for the ASAS-SN team, as they join the ranks of PanSTARRS, LINEAR and other prolific robotic comet hunters.

Evoking the very name “ASAS-SN” seems to have sparked a minor controversy as well, as the International Astronomical Union (IAU) declined to name the comet after the survey, listing it simply as “C/2017 O1”. Word is, “ASAS-SN” was to close to the word “Assassin” (this is actually controversial?) For our money, we’ll simply keep referring to the comet as “O1 ASAS-SN” as a recognition of the team’s hard work and their terrific discovery.

https://www.universetoday.com/136564/new-comet-c2017-o1-asas-sn-takes-earth-surprise/
Title: Re: Exoplanets And Stars Thread
Post by: hop on 07/27/2017 05:18 PM
OK, they found that 3 out of 104 were really false positives, where only one was expected (statistically), then figured out why so it can be avoided in the future.
It's not clear to me Cabrera et al looked at all 104 of those planets, they were looking at specific planets for followup.
Quote
Clearly valuable, but it does not change the overall exo-planet statistics much.  If you are trying to do any sort of planetary census, there are much bigger sources of error.  If you are zooming in on one particular star, though, it's worth double checking.
It's also important to note that these are K2 planets. K2 data is open to all: Discoveries are made by whoever publishes first and aren't validated by the Kepler team, so this doesn't necessarily have any implication for the main Kepler catalog. My impression is the normal Kepler validation process includes tests that would have flagged these.
Title: Re: Exoplanets And Stars Thread
Post by: Star One on 07/27/2017 05:42 PM
OK, they found that 3 out of 104 were really false positives, where only one was expected (statistically), then figured out why so it can be avoided in the future.
It's not clear to me Cabrera et al looked at all 104 of those planets, they were looking at specific planets for followup.
Quote
Clearly valuable, but it does not change the overall exo-planet statistics much.  If you are trying to do any sort of planetary census, there are much bigger sources of error.  If you are zooming in on one particular star, though, it's worth double checking.
It's also important to note that these are K2 planets. K2 data is open to all: Discoveries are made by whoever publishes first and aren't validated by the Kepler team, so this doesn't necessarily have any implication for the main Kepler catalog. My impression is the normal Kepler validation process includes tests that would have flagged these.

Thanks for clarifying this was for K2, as that makes my posts up thread irrelevant here.
Title: Re: Exoplanets And Stars Thread
Post by: Star One on 07/27/2017 06:50 PM
A Tale of Three Stellar Cities

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Using new observations from ESO’s VLT Survey Telescope, astronomers have discovered three different populations of young stars within the Orion Nebula Cluster. This unexpected discovery adds very valuable new insights for the understanding of how such clusters form. It suggests that star formation might proceed in bursts, where each burst occurs on a much faster time-scale than previously thought.

OmegaCAM — the wide-field optical camera on ESO’s VLT Survey Telescope (VST) — has captured the spectacular Orion Nebula and its associated cluster of young stars in great detail, producing a beautiful new image. This object is one of the closest stellar nurseries for both low and high-mass stars, at a distance of about 1350 light-years [1].

But this is more than just a pretty picture. A team led by ESO astronomer Giacomo Beccari has used these data of unparallelled quality to precisely measure the brightness and colours of all the stars in the Orion Nebula Cluster. These measurements allowed the astronomers to determine the mass and ages of the stars. To their surprise, the data revealed three different sequences of potentially different ages.

“Looking at the data for the first time was one of those ‘Wow!’ moments that happen only once or twice in an astronomer's lifetime,” says Beccari, lead ­author of the paper presenting the results. “The incredible quality of the OmegaCAM images revealed without any doubt that we were seeing three distinct populations of stars in the central parts of Orion.”

Monika Petr-Gotzens, co-author and also based at ESO Garching, continues, “This is an important result. What we are witnessing is that the stars of a cluster at the beginning of their lives didn’t form altogether simultaneously. This may mean that our understanding of how stars form in clusters needs to be modified.”

The astronomers looked carefully at the possibility that instead of indicating different ages, the different brightnesses and colours of some of the stars were due to hidden companion stars, which would make the stars appear brighter and redder than they really were. But this idea would imply quite unusual properties of the pairs, which have never before been observed. Other measurements of the stars, such as their rotation speeds and spectra, also indicated that they must have different ages [2].

“Although we cannot yet formally disprove the possibility that these stars are binaries, it seems much more natural to accept that what we see are three generations of stars that formed in succession, within less than three million years,” concludes Beccari.

The new results strongly suggest that star formation in the Orion Nebula Cluster is proceeding in bursts, and more quickly than had been previously thought.

http://www.eso.org/public/news/eso1723/
Title: Re: Exoplanets And Stars Thread
Post by: Star One on 07/27/2017 08:16 PM
BBC article with additional reporting on the story.

Signal may be from first 'exomoon'

Quote
But Dr Kipping said this is not the best way to gauge the potential detection.
He told BBC News: "We're excited about it... statistically, formally, it's a very high probability. But do we really trust the statistics? That's something unquantifiable. Until we get the measurements from Hubble, it may as well be 50-50 in my mind."
The candidate moon is known as Kepler-1625b I and is observed around a star that lies some 4,000 light-years from Earth. On account of its large size, team members have dubbed it a "Nep-moon".
A current theory of planetary formation suggests such an object is unlikely to have formed in place with its Jupiter-mass planet, but would instead be an object captured by the gravity of the planet later on in the evolution of this planetary system.
The researchers could find no predictions of a Neptune-sized moon in the literature, but Dr Kipping notes that nothing in physics prevents one.
A handful of possible candidates have come to light in the past, but none as yet has been confirmed.
"I'd say it's the best [candidate] we've had," Dr Kipping told me.
"Almost every time we hit a candidate, and it passes our tests, we invent more tests until it finally dies - until it fails one of the tests... in this case we've applied everything we've ever done and it's passed all of those tests. On the other hand, we only have three events."

http://www.bbc.co.uk/news/science-environment-40741545
Title: Re: Exoplanets And Stars Thread
Post by: hop on 07/28/2017 07:31 AM
Here's Alex Teachey and David Kipping (authors of the exomoon paper) talking about the result, and why they ended up going public now

Title: Re: Exoplanets And Stars Thread
Post by: Star One on 07/28/2017 09:53 AM
Good news for James Cameron as if you can get moons the size of Neptune there's nothing to say you couldn't get moons the size of Earth around a super sized gas giant. So you would end up with a system as seen in the film like Avatar if you had more than one of them.
Title: Re: Exoplanets And Stars Thread
Post by: rubtest on 07/28/2017 10:06 AM
Was there any search for tiny moons around the biggest MOONS in the solar systems like Titan , Ganymede ?
I am almost sure it is gravitational an impossibility because of the Jupiter / Saturn strong gravitational fields.
Post by: Star One on 07/28/2017 06:52 PM
New Nature article about the possible exomoon discovery with some useful quotes.

Quote
Jean Schneider, an exomoon hunter at the Paris Observatory, says that the authors were right to make this candidate public. Now, he says, “other people can re-analyse the Kepler data for Kepler-1625 b and make their own opinion”.

Astronomer David Bennett at the University of Notre Dame in Indiana agrees. “I don’t consider it to be terribly controversial to put a paper on the arXiv before it is peer reviewed,” he says. “It is often the case that the journal doesn’t really find the best person to review the paper,” he adds. “If it is posted on arXiv.org, then you might get much more useful comments from a real expert who wasn’t picked by the journal to review the paper.”

http://www.nature.com/news/why-astronomers-reluctantly-announced-a-possible-exomoon-discovery-1.22377
Title: Re: Exoplanets And Stars Thread
Post by: Dao Angkan on 08/01/2017 02:36 AM
Four new short-period giant planets discovered (https://phys.org/news/2017-07-short-period-giant-planets.html)

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Astronomers have detected four new giant exoplanets as part of the Hungarian-made Automated Telescope Network-South (HATSouth) exoplanet survey. The newly found alien worlds are about the size of Jupiter, but less massive. They transit moderately bright stars and have short orbital periods.

Quote
According to the paper, HATS-45b is the largest and most massive exoworld of all the newly discovered exoplanets. It has a radius of about 1.29 Jupiter radii and is 30 percent less massive than our solar system's biggest planet. It orbits its parent star every 4.19 days.

HATS-46b has the longest orbital period and is the least massive of the newly found quartet. It has only 17 percent of the mass of Jupiter, however a radius of approximately 0.9 Jupiter radii. It takes this planet 4.74 days to fully circle its host.

HATS-43b and HATS-44b are similar in radius—1.18 and 1.07 Jupiter radii respectively. HATS-43b has a mass of 0.26 Jupiter masses, while HATS-44b is about two times more massive—0.56 Jupiter masses. The shortest orbital period among the four newly identified planets belongs to HATS-44b, which orbits its star in just 2.74 days. When it comes to HATS-43b, it takes it approximately 4.39 days to circle its parent star.
Title: Re: Exoplanets And Stars Thread
Post by: Phil Stooke on 08/01/2017 02:57 AM
"Was there any search for tiny moons around the biggest MOONS in the solar systems like Titan , Ganymede ?"

I can't give a source at the moment, but I believe there have been searches for rings and moons around the larger moons of Saturn, at least.
Title: Re: Exoplanets And Stars Thread
Post by: Star One on 08/01/2017 04:40 PM

Exomoons: Rare in Inner Stellar Systems?

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With all this in mind, every paper that comes out of HEK gets my attention. Kipping (Columbia University), working with graduate student Alex Teachey and citizen scientist Allan Schmitt, has now produced a paper that takes a significant step as the investigation proceeds. We have no detection yet — more about that in a moment — but we do have a broader result showing that exomoons are unusual in the inner regions of the systems surveyed.

Kipping and Teachey looked at 284 viable moon-hosting Kepler planetary candidates to search for moons around planets from Earth to Jupiter in size and distances from their stars of 0.1 to 1 AU. This finding seems to be getting less attention in the press than it deserves, so let’s dig into the paper on it:

Our results place new upper limits on the exomoon population for planets orbiting within about 1 AU of their host star, upper limits that are remarkably low. We have also analyzed subsets of the ensemble to test the effect of various data cuts, and we have identified the regime in which the OSE model presented in Heller (2014) breaks down, which we call the “Callisto Effect” — beyond 20 planetary radii, discrepancies appear in the results.

Quote
Back to the paper:

Our analysis suggests that exomoons may be quite rare around planets at small semi-major axes, a finding that supports theoretical work suggesting moons may be lost as planets migrate inward. On the other hand, if the dearth of exomoons can be read as a reliable indicator of migration, our results suggest a large fraction of the planets in the ensemble have migrated to their present location.

And that is a pointer to which we need to pay attention. Is a lack of exomoons a marker for planetary migration? If further analysis determines that it is, then we’ve found an extremely handy tool for studying the formation history of other stellar systems

https://www.centauri-dreams.org/?p=38214
Post by: Star One on 08/03/2017 08:32 AM
Hubble detects exoplanet with glowing water atmosphere

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Scientists have discovered the strongest evidence to date for a stratosphere on a planet outside our solar system, or exoplanet. A stratosphere is a layer of atmosphere in which temperature increases with higher altitudes.

“This result is exciting because it shows that a common trait of most of the atmospheres in our solar system — a warm stratosphere — also can be found in exoplanet atmospheres,” said Mark Marley, study co-author based at NASA’s Ames Research Center in California’s Silicon Valley. “We can now compare processes in exoplanet atmospheres with the same processes that happen under different sets of conditions in our own solar system.”

Reporting in the journal Nature, scientists used data from NASA’s Hubble Space Telescope to study WASP-121b, a type of exoplanet called a “hot Jupiter.” Its mass is 1.2 times that of Jupiter, and its radius is about 1.9 times Jupiter’s — making it puffier. But while Jupiter revolves around our sun once every 12 years, WASP-121b has an orbital period of just 1.3 days. This exoplanet is so close to its star that if it got any closer, the star’s gravity would start ripping it apart. It also means that the top of the planet’s atmosphere is heated to a blazing 4,600 degrees Fahrenheit (2,500 degrees Celsius), hot enough to boil some metals. The WASP-121 system is estimated to be about 900 light-years from Earth — a long way, but close by galactic standards.

https://astronomynow.com/2017/08/02/hubble-detects-exoplanet-with-glowing-water-atmosphere/

Astronomers discover ‘heavy metal’ supernova rocking out

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Following the recent discovery of one of these “superluminous supernovas”, a team of astronomers led by Matt Nicholl from the Harvard-Smithsonian Center for Astrophysics (CfA) in Cambridge, Mass., has uncovered vital clues about where some of these extraordinary objects come from.

Cambridge University’s Gaia Science Alerts team discovered this supernova, dubbed SN 2017egm, on May 23, 2017 with the European Space Agency’s Gaia satellite. A team led by Subo Dong of the Kavli Institute for Astronomy and Astrophysics at Peking University used the Nordic Optical Telescope to identify it as a superluminous supernova.

SN 2017egm is located in a spiral galaxy about 420 million light years from Earth, making it about three times closer than any other superluminous supernova previously seen. Dong realized that the galaxy was very surprising, as virtually all known superluminous supernovas have been found in dwarf galaxies that are much smaller than spiral galaxies like the Milky Way.

Building on this discovery, the CfA team found that SN 2017egm’s host galaxy has a high concentration of elements heavier than hydrogen and helium, which astronomers call “metals”. This is the first clear evidence for a metal-rich birthplace for a superluminous supernova. The dwarf galaxies that usually host superluminous supernovas are known to have a low metal content, which was thought to be an essential ingredient for making these explosions.

“Superluminous supernovas were already the rock stars of the supernova world,” said Nicholl. “We now know that some of them like heavy metal, so to speak, and explode in galaxies like our own Milky Way.”

https://astronomynow.com/2017/08/02/astronomers-discover-heavy-metal-supernova-rocking-out/
Title: Re: Exoplanets And Stars Thread
Post by: Star One on 08/03/2017 07:33 PM
Disintegrating Rocky Exoplanets

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We discuss a new class of exoplanets that appear to be emitting a tail of dusty effluents. These disintegrating planets are found close to their host stars and have very hot, and likely molten, surfaces. The properties of the dust should provide a direct probe of the constituent material of these rocky bodies.

https://arxiv.org/abs/1708.00633
Title: Re: Exoplanets And Stars Thread
Post by: Star One on 08/03/2017 07:53 PM
Gravity Waves Detected In Sun's Interior Reveal Rapidly Rotating Core

Quote
Scientists using the ESA/NASA SOHO solar observatory have found long-sought gravity modes of seismic vibration that imply the Sun’s core is rotating four times faster than its surface.

http://m.esa.int/Our_Activities/Space_Science/Space_Science/Gravity_waves_detected_in_Sun_s_interior_reveal_rapidly_rotating_core
Title: Re: Exoplanets And Stars Thread
Post by: Star One on 08/04/2017 08:10 PM
Bad News For Proxima b: An Earth-Like Atmosphere Might Not Survive There

Quote
So it’s not all bad news, but it doesn’t inspire a lot of confidence either. Unless Proxima b is a volcanically-active planet and subject to a lot of cometary impacts, it is not likely be temperate, water-bearing world. Most likely, its climate will be analogous to Mars – cold, dry, and with water existing mostly in the form of ice. And as for indigenous life emerging there, that’s not too likely either.

These and other recent studies have painted a rather bleak picture about the habitability of red dwarf star systems. Given that these are the most common types of stars in the known Universe, the statistical likelihood of finding a habitable planet beyond our Solar System appears to be dropping. Not exactly good news at all for those hoping that life will be found out there within their lifetimes!

But it is important to remember that what we can say definitely at this point about extra-solar planets is limited. In the coming years and decades, next-generation missions – like the James Webb Space Telescope (JWST) and the Transiting Exoplanet Survey Satellite (TESS) –  are sure to paint a more detailed picture. In the meantime, there’s still plenty of stars in the Universe, even if most of them are extremely far away!

Title: Re: Exoplanets And Stars Thread
Post by: Dao Angkan on 08/09/2017 02:56 PM
Four Earth-sized planets detected orbiting the nearest sun-like star (https://news.ucsc.edu/2017/08/tau-ceti-planets.html)

(http://i.imgur.com/Lyin3Sf.jpg)

(http://i.imgur.com/hIXxlWJ.png)

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A new study by an international team of astronomers reveals that four Earth-sized planets orbit the nearest sun-like star, tau Ceti, which is about 12 light years away and visible to the naked eye. These planets have masses as low as 1.7 Earth mass, making them among the smallest planets ever detected around nearby sun-like stars. Two of them are super-Earths located in the habitable zone of the star, meaning they could support liquid surface water.

The planets were detected by observing the wobbles in the movement of tau Ceti. This required techniques sensitive enough to detect variations in the movement of the star as small as 30 centimeters per second.

"We are now finally crossing a threshold where, through very sophisticated modeling of large combined data sets from multiple independent observers, we can disentangle the noise due to stellar surface activity from the very tiny signals generated by the gravitational tugs from Earth-sized orbiting planets," said coauthor Steven Vogt, professor of astronomy and astrophysics at UC Santa Cruz.

According to lead author Fabo Feng of the University of Hertfordshire, UK, the researchers are getting tantalizingly close to the 10-centimeter-per-second limit required for detecting Earth analogs. "Our detection of such weak wobbles is a milestone in the search for Earth analogs and the understanding of the Earth's habitability through comparison with these analogs," Feng said. "We have introduced new methods to remove the noise in the data in order to reveal the weak planetary signals."

The outer two planets around tau Ceti are likely to be candidate habitable worlds, although a massive debris disc around the star probably reduces their habitability due to intensive bombardment by asteroids and comets.

The same team also investigated tau Ceti four years ago in 2013, when coauthor Mikko Tuomi of the University of Hertfordshire led an effort in developing data analysis techniques and using the star as a benchmark case. "We came up with an ingenious way of telling the difference between signals caused by planets and those caused by star's activity. We realized that we could see how star's activity differed at different wavelengths and use that information to separate this activity from signals of planets," Tuomi said.

The researchers painstakingly improved the sensitivity of their techniques and were able to rule out two of the signals the team had identified in 2013 as planets. "But no matter how we look at the star, there seem to be at least four rocky planets orbiting it," Tuomi said. "We are slowly learning to tell the difference between wobbles caused by planets and those caused by stellar active surface. This enabled us to essentially verify the existence of the two outer, potentially habitable planets in the system."

Color difference makes a difference: four planet candidates around tau Ceti (https://arxiv.org/abs/1708.02051)

If confirmed, there would seem to be decent room for an Earth mass planet in the middle of the habitable zone which wouldn't currently be detectable.
Title: Re: Exoplanets And Stars Thread
Post by: Star One on 08/09/2017 06:49 PM
Is Tau Ceti more sunlike than either of the Alpha Centauri stars then?
Title: Re: Exoplanets And Stars Thread
Post by: Bob Shaw on 08/09/2017 07:12 PM
Have any planets been *really* detected around Bernard's Star? It would be rather nice!
Title: Re: Exoplanets And Stars Thread
Post by: zubenelgenubi on 08/09/2017 07:37 PM
Re: nearest sun-like star

Star                      Mass, in solar masses   Spectral Type (Sun = G2V)

Alpha Centauri A    1.10                           G2V

Alpha Centauri B    0.91                            K1V

Sirius A                 2.02                            A1V

Epsilon Eridani       0.82                            K2V

Procyon A             1.50                            F5V-IV

Epsilon Indi A        0.76                             K5V

Tau Ceti                0.78                            G8V

They may be applying data in a partly-subjective manner to claim "nearest sun-like star:"
distance, Main Sequence star near 1 solar mass, not part of a binary or multiple star system, etc.
Title: Re: Exoplanets And Stars Thread
Post by: Bynaus on 08/09/2017 07:38 PM
It is noteworthy that if the planetary system is aligned with the debris disk (which seems very likely), the true masses of the four planets are about double their minimum masses. So the inner two planets would be large super-Earths, whereas the outer two would be mini-Neptunes.

@StarOne: I think of these three stars, Alpha Cen A is most sun-like. It is also a G2V type, is only 10% more massive and has a similar rotation period. Then Tau Ceti, then Alpha Cen B.

@Bob Shaw: the planets that van de Kamp thought were there (in the 1960ies) do not exist, this we know for sure. Otherwise, we only have upper limits on mass/distance (<7.5 Earth masses in the habitable zone, e.g.). The Red Dots (https://twitter.com/RedDotsSpace) project is bound to find out!
Title: Re: Exoplanets And Stars Thread
Post by: Star One on 08/09/2017 08:23 PM
It is noteworthy that if the planetary system is aligned with the debris disk (which seems very likely), the true masses of the four planets are about double their minimum masses. So the inner two planets would be large super-Earths, whereas the outer two would be mini-Neptunes.

@StarOne: I think of these three stars, Alpha Cen A is most sun-like. It is also a G2V type, is only 10% more massive and has a similar rotation period. Then Tau Ceti, then Alpha Cen B.

@Bob Shaw: the planets that van de Kamp thought were there (in the 1960ies) do not exist, this we know for sure. Otherwise, we only have upper limits on mass/distance (<7.5 Earth masses in the habitable zone, e.g.). The Red Dots (https://twitter.com/RedDotsSpace) project is bound to find out!

Thank you. Could you direct me towards any articles or papers speculating on the origins of the debris disk around Tau Ceti?
Title: Re: Exoplanets And Stars Thread
Post by: Bynaus on 08/09/2017 08:34 PM
It is noteworthy that if the planetary system is aligned with the debris disk (which seems very likely), the true masses of the four planets are about double their minimum masses. So the inner two planets would be large super-Earths, whereas the outer two would be mini-Neptunes.

@StarOne: I think of these three stars, Alpha Cen A is most sun-like. It is also a G2V type, is only 10% more massive and has a similar rotation period. Then Tau Ceti, then Alpha Cen B.

@Bob Shaw: the planets that van de Kamp thought were there (in the 1960ies) do not exist, this we know for sure. Otherwise, we only have upper limits on mass/distance (<7.5 Earth masses in the habitable zone, e.g.). The Red Dots (https://twitter.com/RedDotsSpace) project is bound to find out!

Thank you. Could you direct me towards any articles or papers speculating on the origins of the debris disk around Tau Ceti?

Look here for a recent overview of the situation (although still with the originally proposed 5 planets):

The classic paper on the Tau Ceti debris disk is probably this one: http://adsabs.harvard.edu/abs/2004MNRAS.351L..54G
Post by: Star One on 08/09/2017 08:38 PM
It is noteworthy that if the planetary system is aligned with the debris disk (which seems very likely), the true masses of the four planets are about double their minimum masses. So the inner two planets would be large super-Earths, whereas the outer two would be mini-Neptunes.

@StarOne: I think of these three stars, Alpha Cen A is most sun-like. It is also a G2V type, is only 10% more massive and has a similar rotation period. Then Tau Ceti, then Alpha Cen B.

@Bob Shaw: the planets that van de Kamp thought were there (in the 1960ies) do not exist, this we know for sure. Otherwise, we only have upper limits on mass/distance (<7.5 Earth masses in the habitable zone, e.g.). The Red Dots (https://twitter.com/RedDotsSpace) project is bound to find out!

Thank you. Could you direct me towards any articles or papers speculating on the origins of the debris disk around Tau Ceti?

Look here for a recent overview of the situation (although still with the originally proposed 5 planets):

The classic paper on the Tau Ceti debris disk is probably this one: http://adsabs.harvard.edu/abs/2004MNRAS.351L..54G

Thanks that second paper sounds interesting.

Seems likely any life that might have got going would probably have been 'bombed' out of existence by that debris disk.
Title: Re: Exoplanets And Stars Thread
Post by: Dao Angkan on 08/09/2017 08:55 PM
It's only necessary for unicellular photosynthetic organisms to survive long enough that there's enough oxygen in the atmosphere to detect. I'm not convinced that oceans full of unicellular life would be completely wiped out by asteroid and comet impacts.
Title: Re: Exoplanets And Stars Thread
Post by: Star One on 08/09/2017 09:03 PM
It's only necessary for unicellular photosynthetic organisms to survive long enough that there's enough oxygen in the atmosphere to detect. I'm not convinced that oceans full of unicellular life would be completely wiped out by asteroid and comet impacts.

But with that kind of disc isn't there a danger that the bombardment would be so heavy that it would leave the surfaces of these planets something like IO.
Title: Re: Exoplanets And Stars Thread
Post by: Dao Angkan on 08/09/2017 09:18 PM
It's "only" estimated to be 10x the frequency as on Earth, which might be an issue for complex life, but shouldn't be an issue for unicellular life. I would also guess that super Earths are more likely to have denser atmospheres than Earth, which would help to mitigate the higher frequency of impacts to an extent.

Cometary impacts might also be beneficial for life, bringing water and organics.

Title: Re: Exoplanets And Stars Thread
Post by: Bynaus on 08/09/2017 09:42 PM
Note that its just that the mass of the debris disk is estimated to be about 10x the mass of the Kuiper belt. To go from there to a 10x higher bombardment rate on the planets in the system is quite problematic. After all, the Earth is primarily bombarded from the asteroid belt, not the Kuiper belt! Bombardment rates on planets primarily depend on the efficiency of delivery of small bodies to planet-crossing orbits (e.g. through resonances and non-gravitational forces), which in turn depends on the system planetary architecture. We know nothing of planets in the outer part (>1 AU) of the Tau Ceti system. Without a detailed simulation, talk of relative bombardment rates and its implications for life on these planets is pure fantasy.
Title: Re: Exoplanets And Stars Thread
Post by: Dao Angkan on 08/09/2017 10:34 PM
Good point, but I still think it's reasonable to assume a higher frequency of impacts. Still, even if that does have an impact on complex life, it's still possible that unicellular photosynthetic life could recover quickly and it might be possible to detect evidence of (or indeed lack of) oxygen in exoplanet atmospheres in the future.

Title: Re: Exoplanets And Stars Thread
Post by: Star One on 08/10/2017 07:27 PM
Hint of relativity effects in stars orbiting centre of galaxy

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A new analysis of data from ESO’s Very Large Telescope and other telescopes suggests that the orbits of stars around the supermassive black hole at the centre of the Milky Way may show the subtle effects predicted by Einstein’s general theory of relativity. There are hints that the orbit of the star S2 is deviating slightly from the path calculated using classical physics. This tantalising result is a prelude to much more precise measurements and tests of relativity that will be made using the GRAVITY instrument as star S2 passes very close to the black hole in 2018.

https://astronomynow.com/2017/08/10/hint-of-relativity-effects-in-stars-orbiting-centre-of-galaxy/
Title: Re: Exoplanets And Stars Thread
Post by: Star One on 08/11/2017 09:24 PM
Two bright, variable sources with unusual light curves discovered by ASAS-SN

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As part of an ongoing effort by ASAS-SN project (Shappee et al. 2014; Kochanek et al. 2017) to characterize and catalog all bright variable stars, we have discovered two bright, variable sources with unusual light curves---ASASSN-V J033455.88-053957.9 (mean V~13.0) and ASASSN-V J211014.40-242105.3 (mean V~14.5).

ASASSN-V J033455.88-053957.9 raises slowly in brightness by ~0.5 mag in ~1,800 days (ASAS-SN Sky Patrol light curve; data points in red are likely affected by artifacts and should not be taken into consideration). A spectrum of this source was obtained by the RAVE survey (Kunder et al. 2017) giving values of T_eff=3660 K and log g =5.1 cm/s^2, fairly typical for an early-type M-dwarf. The 2MASS colors for this source (J-H=0.59 and H-Ks=0.10) also correspond to M1/M2 spectral type M-dwarf (West et al. 2011). ASASSN-V J033455.88-053957.9 appears in a number of X-ray catalogs, including the Swift X-ray point source catalogue (Evans et al. 2014). ASAS-SN light curve for ASASSN-V J033455.88-053957.9 is very unusual for an M-dwarf, and we encourage further observations of this source.

ASASSN-V J211014.40-242105.3 (ASAS-SN Sky Patrol light curve) is mostly flat at around V~14.5 mag, with a big drop in brightness of at least ~2 mag, lasting at least 150 days. This source was spectroscopically classified as a cataclysmic variable, with Balmer and HeII 4686A emission lines (Kilkenny et al. 2015). We conclude that ASASSN-V J211014.40-242105.3 is most likely a cataclysmic variable (CV) of the VY Scl type.

We thank Las Cumbres Observatory and its staff for their continued support of ASAS-SN. ASAS-SN is funded in part by the Gordon and Betty Moore Foundation through grant GBMF5490 to the Ohio State University, NSF grant AST-1515927, the Mt. Cuba Astronomical Foundation, the Center for Cosmology and AstroParticle Physics (CCAPP) at OSU, and the Chinese Academy of Sciences South America Center for Astronomy (CASSACA).

Title: Re: Exoplanets And Stars Thread
Post by: Star One on 08/12/2017 07:45 PM
TRAPPIST-1 is Older Than Our Solar System

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If we want to know more about whether life could survive on a planet outside our solar system, it's important to know the age of its star. Young stars have frequent releases of high-energy radiation called flares that can zap their planets' surfaces. If the planets are newly formed, their orbits may also be unstable. On the other hand, planets orbiting older stars have survived the spate of youthful flares, but have also been exposed to the ravages of stellar radiation for a longer period of time.

Scientists now have a good estimate for the age of one of the most intriguing planetary systems discovered to date -- TRAPPIST-1, a system of seven Earth-size worlds orbiting an ultra-cool dwarf star about 40 light-years away. Researchers say in a new study that the TRAPPIST-1 star is quite old: between 5.4 and 9.8 billion years. This is up to twice as old as our own solar system, which formed some 4.5 billion years ago.

The seven wonders of TRAPPIST-1 were revealed earlier this year in a NASA news conference, using a combination of results from the Transiting Planets and Planetesimals Small Telescope (TRAPPIST) in Chile, NASA's Spitzer Space Telescope, and other ground-based telescopes. Three of the TRAPPIST-1 planets reside in the star's "habitable zone," the orbital distance where a rocky planet with an atmosphere could have liquid water on its surface. All seven planets are likely tidally locked to their star, each with a perpetual dayside and nightside.

At the time of its discovery, scientists believed the TRAPPIST-1 system had to be at least 500 million years old, since it takes stars of TRAPPIST-1's low mass (roughly 8 percent that of the Sun) roughly that long to contract to its minimum size, just a bit larger than the planet Jupiter. However, even this lower age limit was uncertain; in theory, the star could be almost as old as the universe itself. Are the orbits of this compact system of planets stable? Might life have enough time to evolve on any of these worlds?

"Our results really help constrain the evolution of the TRAPPIST-1 system, because the system has to have persisted for billions of years. This means the planets had to evolve together, otherwise the system would have fallen apart long ago," said Adam Burgasser, an astronomer at the University of California, San Diego, and the paper's first author. Burgasser teamed up with Eric Mamajek, deputy program scientist for NASA's Exoplanet Exploration Program based at NASA's Jet Propulsion Laboratory, Pasadena, California, to calculate TRAPPIST-1's age. Their results will be published in The Astrophysical Journal.

It is unclear what this older age means for the planets' habitability. On the one hand, older stars flare less than younger stars, and Burgasser and Mamajek confirmed that TRAPPIST-1 is relatively quiet compared to other ultra-cool dwarf stars. On the other hand, since the planets are so close to the star, they have soaked up billions of years of high-energy radiation, which could have boiled off atmospheres and large amounts of water. In fact, the equivalent of an Earth ocean may have evaporated from each TRAPPIST-1 planet except for the two most distant from the host star: planets g and h. In our own solar system, Mars is an example of a planet that likely had liquid water on its surface in the past, but lost most of its water and atmosphere to the Sun's high-energy radiation over billions of years.

However, old age does not necessarily mean that a planet's atmosphere has been eroded. Given that the TRAPPIST-1 planets have lower densities than Earth, it is possible that large reservoirs of volatile molecules such as water could produce thick atmospheres that would shield the planetary surfaces from harmful radiation. A thick atmosphere could also help redistribute heat to the dark sides of these tidally locked planets, increasing habitable real estate. But this could also backfire in a "runaway greenhouse" process, in which the atmosphere becomes so thick the planet surface overheats - as on Venus.

"If there is life on these planets, I would speculate that it has to be hardy life, because it has to be able to survive some potentially dire scenarios for billions of years," Burgasser said.

Fortunately, low-mass stars like TRAPPIST-1 have temperatures and brightnesses that remain relatively constant over trillions of years, punctuated by occasional magnetic flaring events. The lifetimes of tiny stars like TRAPPIST-1 are predicted to be much, much longer than the 13.7 billion-year age of the universe (the Sun, by comparison, has an expected lifetime of about 10 billion years).

"Stars much more massive than the Sun consume their fuel quickly, brightening over millions of years and exploding as supernovae," Mamajek said. "But TRAPPIST-1 is like a slow-burning candle that will shine for about 900 times longer than the current age of the universe."

Some of the clues Burgasser and Mamajek used to measure the age of TRAPPIST-1 included how fast the star is moving in its orbit around the Milky Way (speedier stars tend to be older), its atmosphere's chemical composition, and how many flares TRAPPIST-1 had during observational periods. These variables all pointed to a star that is substantially older than our Sun.

Future observations with NASA's Hubble Space Telescope and upcoming James Webb Space Telescope may reveal whether these planets have atmospheres, and whether such atmospheres are like Earth's.

"These new results provide useful context for future observations of the TRAPPIST-1 planets, which could give us great insight into how planetary atmospheres form and evolve, and persist or not," said Tiffany Kataria, exoplanet scientist at JPL, who was not involved in the study.

Future observations with Spitzer could help scientists sharpen their estimates of the TRAPPIST-1 planets' densities, which would inform their understanding of their compositions.

https://exoplanets.nasa.gov/trappist1
Title: Re: Exoplanets And Stars Thread
Post by: Star One on 08/12/2017 07:53 PM
Here's the relevant paper.

On the Age of the TRAPPIST-1 System

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The nearby (d = 12 pc) M8 dwarf star TRAPPIST-1 (2MASS J23062928-0502285) hosts a compact system of at least seven exoplanets with sizes similar to Earth. Given its importance for testing planet formation and evolution theories, and for assessing the prospects for habitability among Earth-size exoplanets orbiting the most common type of star in the Galaxy, we present a comprehensive assessment of the age of this system. We collate empirical age constraints based on the color-absolute magnitude diagram, average density, lithium absorption, surface gravity features, metallicity, kinematics, rotation, and magnetic activity; and conclude that TRAPPIST-1 is a transitional thin/thick disk star with an age of 7.6±2.2 Gyr. The star's color-magnitude position is consistent with it being slightly metal-rich ([Fe/H] ≃ +0.06), in line with its previously reported near-infrared spectroscopic metallicity; and it has a radius (R = 0.121±0.003 R⊙) that is larger by 8-14% compared to solar-metallicity evolutionary models. We discuss some implications of the old age of this system with regard to the stability and habitability of its planets.

https://arxiv.org/abs/1706.02018
Title: Re: Exoplanets And Stars Thread
Post by: Bynaus on 08/14/2017 06:34 AM
A planetary system around near-by YZ Ceti.

https://arxiv.org/abs/1708.03336

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The HARPS search for southern extra-solar planets XLII. A system of Earth-mass planets around the nearby M dwarf YZ Cet

Exoplanet surveys have shown that systems with multiple low-mass planets on compact orbits are common. Except for few cases, however, the masses of these planets are generally unknown. At the very end of the main sequence, host stars have the lowest mass and hence offer the largest reflect motion for a given planet. In that context, we monitored the low-mass (0.13Msun) M dwarf YZ Cet (GJ 54.1, HIP 5643) intensively and obtained both radial velocities and stellar-activity indicators derived from both spectroscopy and photometry. We find strong evidence that it is orbited by at least three planets in compact orbits (P=1.97, 3.06, 4.66 days), with the inner two near a 2:3 mean-motion resonance. The minimum masses are comparable to that of Earth (Msini=0.75+-0.13, 0.98+-0.14, and 1.14+-0.17 Mearth) and also the lowest masses measured by radial velocity so far. We note the possibility for an even lower-mass, fourth planet with Msini=0.472+-0.096 Mearth at P=1.04 days. An n-body dynamical model is used to put further constraints on the system parameters. At 3.6 parsecs, YZ Cet is the nearest multi-planet system detected to date.

Cool factoid: YZ Ceti is a star currently located only 1.6 LY from Tau Ceti.
Post by: Star One on 08/15/2017 07:32 PM
Tidally locked exoplanets may be more common than previously thought

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Many exoplanets to be found by coming high-powered telescopes will probably be tidally locked — with one side permanently facing their host star — according to new research by astronomer Rory Barnes of the University of Washington.

Barnes, a UW assistant professor of astronomy and astrobiology, arrived at the finding by questioning the long-held assumption that only those stars that are much smaller and dimmer than the sun could host orbiting planets that were in synchronous orbit, or tidally locked, as the moon is with the Earth. His paper, “Tidal Locking of Habitable Exoplanets,” has been accepted for publication by the journal Celestial Mechanics and Dynamical Astronomy.

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Barnes writes: “These results suggest that the process of tidal locking is a major factor in the evolution of most of the potentially habitable exoplanets to be discovered in the near future.”

Being tidally locked was once thought to lead to such extremes of climate as to eliminate any possibility of life, but astronomers have since reasoned that the presence of an atmosphere with winds blowing across a planet’s surface could mitigate these effects and allow for moderate climates and life.

Barnes said he also considered the planets that will likely be discovered by NASA’s next planet-hunting satellite, the Transiting Exoplanet Survey Satellite or TESS, and found that every potentially habitable planet it will detect will likely be tidally locked.

http://www.washington.edu/news/2017/08/14/tidally-locked-exoplanets-may-be-more-common-than-previously-thought/
Title: Re: Exoplanets And Stars Thread
Post by: Star One on 08/16/2017 08:00 PM
Tuning Up RV: A Test Case at Tau Ceti

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And so on. The lesson is clear enough: We have to be extremely careful when interpreting signals below 1 meter per second, the range in which we’ll need to identify Earth-class planets.

But the value of radial velocity is unquestioned. Unlike the transit technique, we don’t have to rely on a fortuitous line-up between a distant planetary system and the Earth — we can therefore extend it to all bright stars of interest. Feng and colleagues think we will be able to use new high precision spectrometers along with these emerging statistical and noise models to find a true Earth analog in the coming decade. Thus this work on Tau Ceti, modeling wavelength-dependent noise, becomes a test case of a new noise model framework that can help us filter background noise out of RV observations.

https://www.centauri-dreams.org/?p=38293
Title: Re: Exoplanets And Stars Thread
Post by: Star One on 08/17/2017 03:07 PM
We may have caught supernova debris slamming into neighboring stars

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In a new paper, a large team of researchers notes that a couple of recent supernovae have shown an unexpected excess of blue light. They then go on to describe the supernova SN 2017cbv, which became visible in March of this year. In this case, the supernova was spotted only a day after the explosion took place. Follow-up observations over the next six weeks allowed the team to build up a detailed record of the aftermath of the supernova (called a light curve). This record was then compared to what we'd expect from a typical type-Ia supernova.

Compared to a standard type-Ia supernova, SN 2017cbv showed an excess of light at all wavelengths, including the blue and UV regions. This was mostly pronounced during the first week after the explosion, as the light ramped up toward its peak. At the peak, there was an excess in redder wavelengths than you'd see in a typical type-Ia supernova.

What could cause this? To find out, the team modified a model of type-Ia supernovae to include a shockwave running into a nearby star. The modified model fits the data well and suggests that somewhere between five and 15 percent of the light during the peak came from the shockwave hitting a nearby star.

The model, however, suggests that the companion star was nearly 40 million miles from the white dwarf (which is a bit closer than Mercury is to our Sun). That's right on the far edge of where you'd expect the companion star to be if the two were close enough to share material. However, the authors point out that this model assumes that they're looking at the event-companion with an ideal viewing angle. If the angle is off, it would look dimmer, which would make the companion star appear to be farther away.

https://arstechnica.com/science/2017/08/we-may-have-caught-supernova-debris-slamming-into-neighboring-stars/
Title: Re: Exoplanets And Stars Thread
Post by: CuddlyRocket on 08/18/2017 02:15 AM
One of the commenters identified the paper on arXiv: Early Blue Excess from the Type Ia Supernova 2017cbv and Implications for Its Progenitor (https://arxiv.org/abs/1706.08990).

Unfortunately, they don't say what happened to the companion star. :(
Title: Re: Exoplanets And Stars Thread
Post by: Kesarion on 08/18/2017 08:13 AM
How is it determined if an exoplanet is really orbiting a star?  In other words, there could be some some lost asteroid sized object millions of light years in between us and the star.  Maybe there is an Oort Cloud object eclipsing a star?  It would just periodically move in front of a star to dim the light

As far as I can remember, in order for a Kepler candidate to be confirmed as an exoplanet, they must observe 3 periodic eclipses and also be confirmed by a ground based telescope. That might have changed since 2013 though.
Title: Re: Exoplanets And Stars Thread
Post by: gospacex on 08/18/2017 08:36 AM
How is it determined if an exoplanet is really orbiting a star?  In other words, there could be some some lost asteroid sized object millions of light years in between us and the star.

Asteroid-sized object would not be detectable - the dip is too small.

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Maybe there is an Oort Cloud object eclipsing a star?  It would just periodically move in front of a star to dim the light

In this case, "periodically" would mean "every 500k years".
Title: Re: Exoplanets And Stars Thread
Post by: Star One on 08/18/2017 06:35 PM
Dynamics of a Probable Earth-mass Planet in the GJ 832 System

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The stability of planetary orbits around the GJ 832 star system, which contains inner (GJ 832c) and outer (GJ 832b) planets, is investigated numerically and a detailed phase-space analysis is performed. Special attention is given to the existence of stable orbits for a planet less than 15 M ⊕ that is injected between the inner and outer planets. Thus, numerical simulations are performed for three and four bodies in elliptical orbits (or circular for special cases) by using a large number of initial conditions that cover the selected phase-spaces of the planet's orbital parameters. The results presented in the phase-space maps for GJ 832c indicate the least deviation of eccentricity from its nominal value, which is then used to determine its inclination regime relative to the star–outer planet plane. Also, the injected planet is found to display stable orbital configurations for at least one billion years. Then, the radial velocity curves based on the signature from the Keplerian motion are generated for the injected planets with masses 1 M ⊕ to 15 M ⊕ in order to estimate their semimajor axes and mass limits. The synthetic RV signal suggests that an additional planet of mass ≤15 M ⊕ with a dynamically stable configuration may be residing between 0.25 and 2.0 au from the star. We have provided an estimated number of RV observations for the additional planet that is required for further observational verification.

http://iopscience.iop.org/article/10.3847/1538-4357/aa80e2/meta
Title: Re: Exoplanets And Stars Thread
Post by: Star One on 08/18/2017 07:04 PM
Habitable Planet Reality Check: Tau Ceti

http://www.drewexmachina.com/2017/08/18/habitable-planet-reality-check-tau-ceti/
Title: Re: Exoplanets And Stars Thread
Post by: Star One on 08/18/2017 07:23 PM
Scientists improve brown dwarf weather forecasts

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To make sense of the ups and downs of brightness, scientists had to rethink their assumptions about what was going on in the brown dwarf atmospheres. The best model to explain the variations involves large waves, propagating through the atmosphere with different periods. These waves would make the cloud structures rotate with different speeds in different bands.

University of Arizona researcher Theodora Karalidi used a supercomputer and a new computer algorithm to create maps of how clouds travel on these brown dwarfs.

“When the peaks of the two waves are offset, over the course of the day there are two points of maximum brightness,” Karalidi said. “When the waves are in sync, you get one large peak, making the brown dwarf twice as bright as with a single wave.”

The results explain the puzzling behavior and brightness changes that researchers previously saw. The next step is to try to better understand what causes the waves that drive cloud behavior.

https://astronomynow.com/2017/08/17/scientists-improve-brown-dwarf-weather-forecasts/
Title: Re: Exoplanets And Stars Thread
Post by: Star One on 08/18/2017 09:50 PM
Does this mean now that with the exception of Alpha Centauri all the stars near to Sol are believed to have planets?
Title: Re: Exoplanets And Stars Thread
Post by: CuddlyRocket on 08/18/2017 11:16 PM
Does this mean now that with the exception of Alpha Centauri all the stars near to Sol are believed to have planets?
Proxima Centauri (and its planet) is the 'C' component of the Alpha Centauri system. However, neither Alpha Centauri A or B are known to have planets. Nor does Barnard's Star (4th nearest), Wolf 359 (5th), Sirius (6th), Gliese 65 A and B (7th and 8th), Ross 154 (9th) and Ross 248 (10th)!

(Disregarding brown and white dwarfs - though none of those closer than Ross 248 are known to have planets either.)
Title: Re: Exoplanets And Stars Thread
Post by: Dao Angkan on 08/18/2017 11:19 PM
Only in as far as most stars are believed to have planets. Most of the nearest stars (https://en.wikipedia.org/wiki/List_of_nearest_stars_and_brown_dwarfs) to 16.3 ly* still don't even have candidate planets yet.

*To 21 ly (http://www.johnstonsarchive.net/astro/nearstar.html), as Wikipedia doesn't seem to have a list of stars (https://en.wikipedia.org/wiki/Category:Lists_of_stars) from 16.3 - 20 ly.
Title: Re: Exoplanets And Stars Thread
Post by: redliox on 08/19/2017 05:30 AM
Does this mean now that with the exception of Alpha Centauri all the stars near to Sol are believed to have planets?
Only in as far as most stars are believed to have planets. Most of the nearest stars (https://en.wikipedia.org/wiki/List_of_nearest_stars_and_brown_dwarfs) to 16.3 ly* still don't even have candidate planets yet.

*To 21 ly (http://www.johnstonsarchive.net/astro/nearstar.html), as Wikipedia doesn't seem to have a list of stars (https://en.wikipedia.org/wiki/Category:Lists_of_stars) from 16.3 - 20 ly.

Although fortunately we have TESS and the JWST coming up, I'd like to see an effort to catalog specifically our neighboring stars.  I don't expect it to be easy, but it would be worth it.
Title: Re: Exoplanets And Stars Thread
Post by: Star One on 08/19/2017 08:14 AM
Does this mean now that with the exception of Alpha Centauri all the stars near to Sol are believed to have planets?
Proxima Centauri (and its planet) is the 'C' component of the Alpha Centauri system. However, neither Alpha Centauri A or B are known to have planets. Nor does Barnard's Star (4th nearest), Wolf 359 (5th), Sirius (6th), Gliese 65 A and B (7th and 8th), Ross 154 (9th) and Ross 248 (10th)!

(Disregarding brown and white dwarfs - though none of those closer than Ross 248 are known to have planets either.)

Aren't Pale Red Dot now studying all our local red dwarfs for planets?
Title: Re: Exoplanets And Stars Thread
Post by: Dao Angkan on 08/19/2017 11:38 AM
Does this mean now that with the exception of Alpha Centauri all the stars near to Sol are believed to have planets?
Only in as far as most stars are believed to have planets. Most of the nearest stars (https://en.wikipedia.org/wiki/List_of_nearest_stars_and_brown_dwarfs) to 16.3 ly* still don't even have candidate planets yet.

*To 21 ly (http://www.johnstonsarchive.net/astro/nearstar.html), as Wikipedia doesn't seem to have a list of stars (https://en.wikipedia.org/wiki/Category:Lists_of_stars) from 16.3 - 20 ly.

Although fortunately we have TESS and the JWST coming up, I'd like to see an effort to catalog specifically our neighboring stars.  I don't expect it to be easy, but it would be worth it.

ESPRESSO (https://www.eso.org/public/teles-instr/paranal-observatory/vlt/vlt-instr/espresso/) should also be helpful with that. It's an order of magnitude more sensitive than HARPS and should be online this year (if not already, it saw first light nearly a year ago).
Title: Re: Exoplanets And Stars Thread
Post by: Dao Angkan on 08/19/2017 02:24 PM
Does this mean now that with the exception of Alpha Centauri all the stars near to Sol are believed to have planets?
Proxima Centauri (and its planet) is the 'C' component of the Alpha Centauri system. However, neither Alpha Centauri A or B are known to have planets. Nor does Barnard's Star (4th nearest), Wolf 359 (5th), Sirius (6th), Gliese 65 A and B (7th and 8th), Ross 154 (9th) and Ross 248 (10th)!

(Disregarding brown and white dwarfs - though none of those closer than Ross 248 are known to have planets either.)

Aren't Pale Red Dot now studying all our local red dwarfs for planets?

AFAIK just Proxima Centauri, Barnard's Star, and Ross 154.
Title: Re: Exoplanets And Stars Thread
Post by: Star One on 08/19/2017 02:25 PM
Does this mean now that with the exception of Alpha Centauri all the stars near to Sol are believed to have planets?
Proxima Centauri (and its planet) is the 'C' component of the Alpha Centauri system. However, neither Alpha Centauri A or B are known to have planets. Nor does Barnard's Star (4th nearest), Wolf 359 (5th), Sirius (6th), Gliese 65 A and B (7th and 8th), Ross 154 (9th) and Ross 248 (10th)!

(Disregarding brown and white dwarfs - though none of those closer than Ross 248 are known to have planets either.)

Aren't Pale Red Dot now studying all our local red dwarfs for planets?

AFAIK just Proxima Centauri, Barnard's Star, and Ross 154.

Out of interest what was the criteria for choosing those three out of all the red dwarfs near Sol?
Title: Re: Exoplanets And Stars Thread
Post by: Alpha_Centauri on 08/19/2017 02:42 PM
Because they are visible from La Silla at this time of year and are bright enough for high-res spectroscopy.
Title: Re: Exoplanets And Stars Thread
Post by: Dao Angkan on 08/19/2017 03:21 PM
There is a candidate for a Super Earth (https://arxiv.org/abs/1702.03571) around Lalande 21185, the 6th closest main sequence star / 4th closest star system (it's missing from CuddlyRocket's list).
Title: Re: Exoplanets And Stars Thread
Post by: Hungry4info3 on 08/19/2017 05:33 PM
Aren't Pale Red Dot now studying all our local red dwarfs for planets?
AFAIK just Proxima Centauri, Barnard's Star, and Ross 154.
Out of interest what was the criteria for choosing those three out of all the red dwarfs near Sol?
Because they are visible from La Silla at this time of year and are bright enough for high-res spectroscopy.
To add to that, there has been a shift in in strategy in recent years for radial velocity surveys away from "Sample numerous stars a few times each" to "Sample a few stars numerous times each." The first one easily catches your intermediate- and long-period giant planets, but to get down to low-mass planets, you have to really drill a star to get enough data to overcome statistical noise. Detecting low-mass planets in the solar neighborhood is now finally feasible, so rather than observing all the local M dwarfs in the sky, we're focusing on hitting a few nearby, bright systems.
Title: Re: Exoplanets And Stars Thread
Post by: Star One on 08/19/2017 05:45 PM
Aren't Pale Red Dot now studying all our local red dwarfs for planets?
AFAIK just Proxima Centauri, Barnard's Star, and Ross 154.
Out of interest what was the criteria for choosing those three out of all the red dwarfs near Sol?
Because they are visible from La Silla at this time of year and are bright enough for high-res spectroscopy.
To add to that, there has been a shift in in strategy in recent years for radial velocity surveys away from "Sample numerous stars a few times each" to "Sample a few stars numerous times each." The first one easily catches your intermediate- and long-period giant planets, but to get down to low-mass planets, you have to really drill a star to get enough data to overcome statistical noise. Detecting low-mass planets in the solar neighborhood is now finally feasible, so rather than observing all the local M dwarfs in the sky, we're focusing on hitting a few nearby, bright systems.

Thank you all. I am constantly amazed that we are able to make such fine measurements of objects so far, it almost seems remarkable.
Title: Re: Exoplanets And Stars Thread
Post by: CuddlyRocket on 08/20/2017 08:27 PM
There is a candidate for a Super Earth (https://arxiv.org/abs/1702.03571) around Lalande 21185, the 6th closest main sequence star / 4th closest star system (it's missing from CuddlyRocket's list).

I didn't include Lalande 21185 in my list because I was listing those stars not known to have a planet and this star has a pretty solid candidate. But then I forgot to adjust the ordinal numbering (Sirius should be the 7th nearest etc.)!  :-[
Title: Re: Exoplanets And Stars Thread
Post by: Bynaus on 08/22/2017 07:50 AM
Dynamics of a Probable Earth-mass Planet in the GJ 832 System

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The stability of planetary orbits around the GJ 832 star system, which contains inner (GJ 832c) and outer (GJ 832b) planets, is investigated numerically and a detailed phase-space analysis is performed. Special attention is given to the existence of stable orbits for a planet less than 15 M ⊕ that is injected between the inner and outer planets. Thus, numerical simulations are performed for three and four bodies in elliptical orbits (or circular for special cases) by using a large number of initial conditions that cover the selected phase-spaces of the planet's orbital parameters. The results presented in the phase-space maps for GJ 832c indicate the least deviation of eccentricity from its nominal value, which is then used to determine its inclination regime relative to the star–outer planet plane. Also, the injected planet is found to display stable orbital configurations for at least one billion years. Then, the radial velocity curves based on the signature from the Keplerian motion are generated for the injected planets with masses 1 M ⊕ to 15 M ⊕ in order to estimate their semimajor axes and mass limits. The synthetic RV signal suggests that an additional planet of mass ≤15 M ⊕ with a dynamically stable configuration may be residing between 0.25 and 2.0 au from the star. We have provided an estimated number of RV observations for the additional planet that is required for further observational verification.

http://iopscience.iop.org/article/10.3847/1538-4357/aa80e2/meta

I have to say I find that article a bit weird. Its not like they have detected anything, not even that there is a hint in the data for the presence of an additional planet. All they have is "if there is a planet here, its orbit would be stable". Oh well - a super-Earth way inside Mercury would also be on a stable orbit, but that doesn't mean there is one. But still, you have news sites like this one (https://www.universetoday.com/136837/another-nearby-red-dwarf-star-system-another-possible-exoplanet-discovered/) running with headlines suggesting a planet has been found...
Title: Re: Exoplanets And Stars Thread
Post by: Star One on 08/22/2017 04:30 PM
New Findings on Brown Dwarf Atmospheres

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I often think of brown dwarfs in terms of the planets that might form around them, and the question of whether even these small ‘failed stars’ may be capable of sustaining life. Have a look, for example, at Luhman 16AB, two brown dwarfs in the Sun’s immediate neighborhood. There are some indications of a planet here which, if it were ever confirmed, would make it the second closest known exoplanet to the Earth, at least for now. We can rule out planets of Neptune mass or greater with a period of between one and two years, but future Hubble observations, already approved for August of next year, may tell us more.

https://www.centauri-dreams.org/?p=38327
Title: Re: Exoplanets And Stars Thread
Post by: Star One on 08/22/2017 07:12 PM
On reflection this seems more appropriate in this area.

Likely Transiting Exocomets Detected by Kepler

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We present the first good evidence for exocomet transits of a host star in continuum light in data from the Kepler mission. The Kepler star in question, KIC 3542116, is of spectral type F2V and is quite bright at Kp=10. The transits have a distinct asymmetric shape with a steeper ingress and slower egress that can be ascribed to objects with a trailing dust tail passing over the stellar disk. There are three deeper transits with depths of ≃0.1% that last for about a day, and three that are several times more shallow and of shorter duration. The transits were found via an exhaustive visual search of the entire Kepler photometric data set, which we describe in some detail. We review the methods we use to validate the Kepler data showing the comet transits, and rule out instrumental artifacts as sources of the signals. We fit the transits with a simple dust-tail model, and find that a transverse comet speed of ∼35-50 km s−1 and a minimum amount of dust present in the tail of ∼1016 g are required to explain the larger transits. For a dust replenishment time of ∼10 days, and a comet lifetime of only ∼300 days, this implies a total cometary mass of ≳3×1017 g, or about the mass of Halley's comet. We also discuss the number of comets and orbital geometry that would be necessary to explain the six transits detected over the four years of Kepler prime-field observations. Finally, we also report the discovery of a single comet-shaped transit in KIC 11084727 with very similar transit and host-

https://arxiv.org/abs/1708.06069
Title: Re: Exoplanets And Stars Thread
Post by: Star One on 08/24/2017 12:34 AM
The META detections. Somewhat before my time so I had never heard of these before. Useful links in the description to further reading as well.

Post by: Star One on 08/24/2017 09:59 PM
The CGI in the video makes it look like it has a malevolent face, with two huge staring eyes it even has pupils!

Best Ever Image of a Star’s Surface and Atmosphere

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First map of motion of material on a star other than the Sun

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Using ESO’s Very Large Telescope Interferometer astronomers have constructed the most detailed image ever of a star — the red supergiant star Antares. They have also made the first map of the velocities of material in the atmosphere of a star other than the Sun, revealing unexpected turbulence in Antares’s huge extended atmosphere. The results were published in the journal Nature.

http://www.eso.org/public/news/eso1726/

Title: Re: Exoplanets And Stars Thread
Post by: Star One on 08/29/2017 07:29 PM
Likely Transiting Exocomets Detected by Kepler by Visual Lightcurve Inspection

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In January 2017, amateur astronomer Tom Jacobs proposed the idea of visually surveying the complete Q1-Q17 Kepler lightcurve archive spanning 201,250 target stars for Data Release 25 (Thompson et al. 2016) with professional astronomers Saul Rappaport and Andrew Vanderburg along with amateur astronomer Daryll LaCourse. "The survey was conducted using the LcTools software system (Kipping et al. 2015), a publicly available Windows-based set of applications designed for processing lightcurves in a fast and efficient manner. Two primary components from the system were utilized; LcGenerator for building lightcurves in bulk and LcViewer for visually inspecting plots of the lightcurve for signals of interest."

The team has worked on similar projects with the K2 campaigns. The survey lasted five months with one person (TJ) individually inspecting each lightcurve for interesting objects that were non periodic in nature. There were no predetermined search parameters. Everything was on the table and numerous flagged objects turned out to be data breaks and data processing anomalies (data glitches) upon subsequent analysis by Saul Rappaport and Andrew Vanderburg. Both veterans were indefatigable in supporting the search effort. On March 18th, KIC 35421116 was initially flagged for its three aperiodic transits and subsequently labeled and analyzed as exocomet candidates.

http://keplerlightcurves.blogspot.co.uk/2017/08/likely-transiting-exocomets-detected-by.html?m=1
Title: Re: Exoplanets And Stars Thread
Post by: Star One on 08/29/2017 07:34 PM
Kepler space telescope discovers variability in the Seven Sisters

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Most of the seven stars are revealed to be slowly-pulsating B stars, a class of variable star in which the star’s brightness changes with day-long periods. The frequencies of these pulsations are key to  exploring some of the poorly understood processes in the core of these stars.

The seventh star, Maia, is different: it varies with a regular period of 10 days. Previous studies have shown that Maia belongs to a class of stars with abnormal surface concentrations of some chemical elements such as manganese. To see if these things were related, a series of spectroscopic observations were taken with the Hertzsprung SONG Telescope.

“What we saw was that the brightness changes seen by Kepler go hand-in-hand with changes in the strength of manganese absorption in Maia’s atmosphere,” said Dr. Victoria Antoci, a co-author of the work and Assistant Professor at the Stellar Astrophysics Centre, Aarhus University. “We conclude that the variations are caused by a large chemical spot on the surface of the star, which comes in and out of view as the star rotates with a ten day period.”

“Sixty years ago, astronomers had thought they could see variability in Maia with periods of a few hours and suggested this was the first of a whole new class of variable stars they called ‘Maia Variables’,” White said, “but our new observations show that Maia is not itself a Maia Variable!”

No signs of exoplanetary transits were detected in this study, but the authors show that their new algorithm can attain the precision that will be needed for Kepler and future space telescopes such as the Transiting Exoplanet Survey Satellite (TESS) to detect planets transiting stars as bright as our neighbouring star Alpha Centauri. These nearby bright stars are the best targets for future missions and facilities such as the James Webb Space Telescope, which is due to launch in late 2018.

https://astronomynow.com/2017/08/29/kepler-space-telescope-discovers-variability-in-the-seven-sisters/
Post by: Star One on 08/30/2017 07:00 PM
Exoplanet-Hunters Detect Two New “Warm Jupiters”

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The study of extra-solar planets has turned up some rather interesting candidates in the past few years. As of August 1st, 2017, a total of 3,639 exoplanets have been discovered in 2,729 planetary systems and 612 multiple planetary systems. Many of these discoveries have challenged conventional thinking about planets, especially where their sizes and distances from their suns are concerned.

According to a study by an international team of astronomers, the latest exoplanet discoveries are in keeping with this trend. Known as EPIC 211418729b and EPIC 211442297b, these two gas giants orbit stars that are located about 1569 and 1360 light-years from Earth (respectively) and are similar in size to Jupiter. Combined with their relatively close orbit to their stars, the team has designated them as “Warm Jupiters”.

The study, titled “EPIC 211418729b and EPIC 211442297b: Two Transiting Warm Jupiters“, recently appeared online. Led by Avi Shporer – a postdoctoral scholar with the Geological and Planetary Sciences (GPS) division at the California Institute of Technology (Caltech) – the team relied on data from the Kepler and K2 missions, and follow-up observations with multiple ground-based telescopes, to determine the sizes, masses and orbits of these planets.

https://www.universetoday.com/137001/exoplanet-hunters-detect-two-new-warm-jupiters/
Title: Re: Exoplanets And Stars Thread
Post by: Star One on 08/31/2017 05:57 AM
Distant galaxy sends out 15 high-energy radio bursts

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Breakthrough Listen, an initiative to find signs of intelligent life in the universe, has detected 15 brief but powerful radio pulses emanating from a mysterious and repeating source – FRB 121102 – far across the universe.

Fast radio bursts are brief, bright pulses of radio emission from distant but largely unknown sources, and FRB 121102 is the only one known to repeat: more than 150 high-energy bursts have been observed coming from the object, which was identified last year as a dwarf galaxy about 3 billion light years from Earth.

Possible explanations for the repeating bursts range from outbursts from rotating neutron stars with extremely strong magnetic fields – so-called magnetars – to a more speculative idea: They are directed energy sources, powerful laser bursts used by extraterrestrial civilizations to power spacecraft, akin to Breakthrough Starshot's plan to use powerful laser pulses to propel nano-spacecraft to Earth's nearest star, Proxima Centauri.

"Bursts from this source have never been seen at this high a frequency," said Andrew Siemion, director of the Berkeley SETI Research Center and of the Breakthrough Listen program.

Title: Re: Exoplanets And Stars Thread
Post by: Star One on 08/31/2017 10:24 PM
Close encounters of the stellar kind

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Understanding the past and future motions of stars is a key goal of Gaia as it collects precise data on stellar positions and motions over its five-year mission. After 14 months, the first catalogue of more than a billion stars was recently released, which included the distances and the motions across the sky for more than two million stars.

By combining the new results with existing information, astronomers began a detailed, large-scale search for stars passing close to our sun.

So far, the motions relative to the sun of more than 300 000 stars have been traced through the galaxy and their closest approach determined for up to five million years in the past and future.

Of them, 97 stars were found that will pass within 150 trillion kilometres, while 16 come within about 60 trillion km.

While the 16 are considered reasonably near, a particularly close encounter of one star, Gliese 710, in 1.3 million years' time, stands out. It is predicted to pass within just 2.3 trillion km or about 16 000 Earth–sun distances, well within the Oort Cloud.

The star is already well-documented, and thanks to the Gaia data, the estimated encounter distance has recently been revised. Previously, there was a 90% degree of certainty that it would come within 3.1–13.6 trillion kilometres. Now, the more accurate data suggest that it will come within 1.5–3.2 trillion km, with 2.3 trillion km most likely.

Furthermore, although Gliese 710 has a mass of 60% that of our sun, it travels much slower than most stars: nearly 50 000 km/h at closest approach, compared with the average 100 000 km/h.

The speed of its passage means it will have plenty of time to exert its gravitational influence on bodies in the Oort Cloud, potentially sending showers of comets into the solar system.

Despite its slower pace, it will still appear as the brightest, fastest object in the night sky at closest approach.

https://m.phys.org/news/2017-08-encounters-stellar-kind.html
Title: Re: Exoplanets And Stars Thread
Post by: Star One on 09/01/2017 07:12 PM
Asteroseismic masses of retired planet-hosting A-stars using SONG

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To better understand how planets form, it is important to study planet occurrence rates as a function of stellar mass. However, estimating masses of field stars is often difficult. Over the past decade, a controversy has arisen about the inferred occurrence rate of gas-giant planets around evolved intermediate-mass stars -- the so-called `retired A-stars'. The high masses of these red-giant planet hosts, derived using spectroscopic information and stellar evolution models, have been called into question. Here we address the controversy by determining the masses of eight evolved planet-hosting stars using asteroseismology. We compare the masses with spectroscopic-based masses from the Exoplanet Orbit Database that were previously adopted to infer properties of the exoplanets and their hosts. We find a significant one-sided offset between the two sets of masses for stars with spectroscopic masses above roughly 1.6Msun, suggestive of an average 15--20% overestimate of the adopted spectroscopic-based masses. The only star in our sample well below this mass limit is also the only one not showing this offset. Finally, we note that the scatter across literature values of spectroscopic-based masses often exceed their formal uncertainties, making it comparable to the offset we report here.

https://arxiv.org/abs/1708.09613
Post by: Star One on 09/01/2017 07:22 PM
In relation to Gliese 710 I know the Sun couldn't capture another star if it wandered close to the Solar System, but could it capture something less massive like a brown dwarf if one did the same thing?

Title: Re: Exoplanets And Stars Thread
Post by: whitelancer64 on 09/01/2017 07:55 PM
In relation to Gliese 710 I know the Sun couldn't capture another star if it wandered close to the Solar System, but could it capture something less massive like a brown dwarf if one did the same thing?

No, and for the same reason. In order to be captured, the object has to slow down. The only way for a body wandering close to our star to be captured by its gravity is for the body to exchange momentum with another body - for example, by gravitationally interacting with Jupiter and throwing it into a different orbit, or ejecting it from the Solar System entirely.
Title: Re: Exoplanets And Stars Thread
Post by: Star One on 09/01/2017 08:22 PM
In relation to Gliese 710 I know the Sun couldn't capture another star if it wandered close to the Solar System, but could it capture something less massive like a brown dwarf if one did the same thing?

No, and for the same reason. In order to be captured, the object has to slow down. The only way for a body wandering close to our star to be captured by its gravity is for the body to exchange momentum with another body - for example, by gravitationally interacting with Jupiter and throwing it into a different orbit, or ejecting it from the Solar System entirely.

I suppose that's why if it exists the captured planet theory is disfavoured for planet nine.
Title: Re: Exoplanets And Stars Thread
Post by: CuddlyRocket on 09/01/2017 09:33 PM
In relation to Gliese 710 I know the Sun couldn't capture another star if it wandered close to the Solar System, but could it capture something less massive like a brown dwarf if one did the same thing?

No, and for the same reason. In order to be captured, the object has to slow down. The only way for a body wandering close to our star to be captured by its gravity is for the body to exchange momentum with another body - for example, by gravitationally interacting with Jupiter and throwing it into a different orbit, or ejecting it from the Solar System entirely.

An alternative scenario is where the object that ends up being captured is part of a binary pair. This is one hypothesis for the capture of Triton by Neptune (Neptune’s capture of its moon Triton in a binary-planet gravitational encounter (http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.568.9568&rep=rep1&type=pdf) (pdf)).
Title: Re: Exoplanets And Stars Thread
Post by: Star One on 09/03/2017 09:33 AM
Main reason I am posting this video is he mentions there has been further FRB detections since the announcement above. I like his videos as he keeps a level head unlike some on YouTube & generally makes statements in reference to papers he links to.

Title: Re: Exoplanets And Stars Thread
Post by: Star One on 09/04/2017 04:28 PM
Supermassive black hole discovered near heart of the Milky Way

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An enormous black hole one hundred thousand times more massive than the sun has been found hiding in a toxic gas cloud wafting around near the heart of the Milky Way.

If the discovery is confirmed, the invisible behemoth will rank as the second largest black hole ever seen in the Milky Way after the supermassive black hole known as Sagittarius A* that is anchored at the very centre of the galaxy.

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Oka, whose research is published in the journal Nature Astronomy, said the newly-found black hole could be the core of an old dwarf galaxy that was cannibalised during the formation of the Milky Way billions of years ago.

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All of which points to the fate that awaits the newly-found black hole. In time, Oka said, the object will be drawn towards Sagittarius A* and sink into it, making the supermassive black hole at the heart of the Milky Way even more massive.

https://www.theguardian.com/science/2017/sep/04/supermassive-black-hole-discovered-near-heart-of-the-milky-way
Title: Re: Exoplanets And Stars Thread
Post by: Dao Angkan on 09/04/2017 10:56 PM
A modified CoRoT detrend algorithm and the discovery of a new planetary companion (https://arxiv.org/abs/1709.00351)

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We present MCDA, a modification of the CoRoT detrend algorithm (CDA) suitable to detrend chromatic light curves. By means of robust statistics and better handling of short term variability, the implementation decreases the systematic light curve variations and improves the detection of exoplanets when compared with the original algorithm. All CoRoT chromatic light curves (a total of 65,655) were analysed with our algorithm. Dozens of new transit candidates and all previously known CoRoT exoplanets were rediscovered in those light curves using a box-fitting algorithm. For three of the new cases spectroscopic measurements of the candidates' host stars were retrieved from the ESO Science Archive Facility and used to calculate stellar parameters and, in the best cases, radial velocities. In addition to our improved detrend technique we announce the discovery of a planet that orbits a 0.79+0.08−0.09R⊙ star with a period of 6.71837±0.00001 days and has 0.57+0.06−0.05RJ and 0.15±0.10MJ. We also present the analysis of two cases in which parameters found suggest the existence of possible planetary companions.
Post by: Star One on 09/05/2017 08:59 AM
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Large solar storms, responsible for the northern lights, may have played a role in the strandings of 29 sperm whales in the North Sea early in 2016.

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Dr Vanselow and his colleagues studied the connection between whale strandings and two major solar storms that took place at the very end of December in 2015.
These produced huge displays of the Aurora Borealis that were seen in many parts of Scotland and elsewhere.
Looking specifically at the region around Shetland, the scientists found that these solar events would have caused short-term shifts in the magnetic field of up to 460km, in the area between the islands and Norway.
This could have caused sperm whales in the region to move in the wrong direction.
They also believe that sperm whales see a regular magnetic anomaly off the Norwegian coast as a "geomagnetic mountain chain", a kind of guardrail that prevents them from entering the North Sea.
The solar storms may have nullified this effect, rendering the mountain chain invisible and allowing the whales to swim through into the North Sea.

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Nasa has also been investigating the question of whether solar storms can affect a whole range of cetaceans around the world.
A team of researchers is shortly to publish a research paper on the connection between strandings in Cape Cod and geomagnetic storms. They say the Venselow paper is "well founded".
"It is one potential mechanism for having animals confused, I think it's a credible theory," Dr Antti Pulkkinen, who is leading the Nasa project, told BBC News.
"But does their paper prove that is the case? I don't think so."
"Having looked at this problem from a data analysis point of view, it is not a single factor that contributes to this.
"Things need to line up from multiple different perspectives for these events to take place."

http://www.bbc.co.uk/news/science-environment-41110082
Title: Re: Exoplanets And Stars Thread
Post by: Star One on 09/05/2017 04:32 PM
The Surface UV Environment on Planets Orbiting M-Dwarfs: Implications for Prebiotic Chemistry & Need for Experimental Follow-Up

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Potentially-habitable planets orbiting M-dwarfs are of intense astrobiological interest because they are the only rocky worlds accessible to biosignature search over the next 10+ years due to a confluence of observational effects. Simultaneously, recent experimental and theoretical work suggests that UV light may have played a key role in the origin of life on Earth, and especially the origin of RNA. Characterizing the UV environment on M-dwarfs planets is important to understanding whether life as we know it could emerge on such worlds. In this work, we couple radiative transfer models to observed M-dwarf spectra to determine the UV environment on prebiotic Earth-analog planets orbiting M-dwarfs. We calculate dose rates to quantify the impact of different host stars on prebiotically-important photoprocesses. We find that M-dwarf planets have access to 100-1000 times less bioactive UV fluence than the young Earth. It is unclear whether UV-sensitive prebiotic chemistry that may have been important to abiogenesis, such as the only known prebiotically plausible pathways for pyrimidine ribonucleotide synthesis, could function on M-dwarf planets. This uncertainty affects objects like the recently-discovered habitable-zone planets orbiting Proxima Centauri, TRAPPIST-1, and LHS 1140. Laboratory studies of the sensitivity of putative prebiotic pathways to irradiation level are required to resolve this uncertainty. If steady-state M-dwarf UV output is insufficient to power these pathways, transient elevated UV irradiation due to flares may suffice; laboratory studies can constrain this possibility as well.

https://arxiv.org/abs/1705.02350
Title: Re: Exoplanets And Stars Thread
Post by: Star One on 09/05/2017 09:46 PM
Shocking discovery explains powerful novae

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Employing two powerful telescopes, astronomers at Michigan State University have proven a theory that explains these super-luminous novae and other astronomical explosions. The results, published in the current issue of Nature Astronomy, indicate that powerful shockwaves amplify the explosions beyond any traditional scale for nuclear explosions.

“Astronomers have long thought the energy from novae was dominated by the white dwarf, controlling how much light and energy are emitted,” said Laura Chomiuk, MSU astronomer and study co-author. “What we discovered, however, was a completely different source of energy — shockwaves that can dominate the entire explosion.”

As the explosion begins, it ejects a cooler, slower wave of gaseous material, relatively speaking. Behind it, though, is a hot, fast wave speeding right behind it. The collision of the two ejections produces a shockwave, which results in a spectacular explosion of heat and light.

“The bigger the shock, the brighter the nova,” Chomiuk said. “We believe it’s the speed of the second wave that influences the explosion.”

This study explains a theory held by Brian Metzger, Columbia University astronomer, who also is a co-author for this paper.

Now that the theory has been proven, astronomers use novae to better understand other super-charged explosions, like those that mark the death of massive stars in galaxies far away.

https://astronomynow.com/2017/09/05/shocking-discovery-explains-powerful-novae/
Post by: Star One on 09/06/2017 07:09 PM
X-rays reveal temperament of possible planet-hosting stars

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A new X-ray study has revealed that stars like the Sun and their less massive cousins calm down surprisingly quickly after a turbulent youth. This result has positive implications for the long-term habitability of planets orbiting such stars.

https://astronomynow.com/2017/09/06/x-rays-reveal-temperament-of-possible-planet-hosting-stars/

Study of Uranus suggests some of its moons are on a collision course

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In studying the orbits of the moons, the researchers found that Cressida is on a path that will cause it to collide with another moon called Desdemona, which currently moves in an orbit just 900 kilometers from Cressida's. The gravity of Cressida is slowly pulling them closer together and will cause them to crash into one another in approximately 1 million years. They also found the same to be true for Cupid and Belinda, which will collide sometime later.

The researchers note that material in the inner rings around Uranus appears likely to be the remnants of other moons that were destroyed when they collided.

https://phys.org/news/2017-09-uranus-moons-collision.amp
Title: Re: Exoplanets And Stars Thread
Post by: Star One on 09/07/2017 04:41 PM
Astrometric exoplanet detectability and the Earth orbital motion

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Astrometric exoplanet discovery relies on detection of stellar motion caused by planetary companions. Systems with orbital period close to one year may escape detection if orbital motion of their host stars are observationally indistinguishable from parallax effect. Additionally, astrometric solution may produce a biased parallax estimation for such systems. We examine effects of orbital motion of the Earth on astrometric detectability in terms of correlation between the Earth's orbital position and position of the star relative to system barycentre. The χ2 statistic for parallax estimation is calculated analytically, leading to expressions that relate the decrease in detectability and accompanying parallax bias to the position correlation function. The effects of the Earth motion's critically depend on orbital period, diminishing rapidly as period deviates from one year. Selection effects against one-year period systems is therefore expected. Statistical estimation shows that corresponding loss of sensitivity is equivalent to a 10 per cent increase in detection threshold. Consideration of eccentric orbits shows that the Earth's motion has no effect on detectability for e≥0.5. Dependence of detectability on other parameters, such as orbital phases and inclination of the orbit plane to the ecliptic, are smooth and monotonic because they are described by simple trigonometric functions.

https://arxiv.org/abs/1709.00290
Title: Re: Exoplanets And Stars Thread
Post by: Star One on 09/07/2017 07:16 PM
Extreme’ telescopes find the second-fastest-spinning pulsar

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By following up on mysterious high-energy sources mapped out by NASA’s Fermi Gamma-ray Space Telescope, the Netherlands-based Low Frequency Array (LOFAR) radio telescope has identified a pulsar spinning at more than 42,000 revolutions per minute, making it the second-fastest known.

https://astronomynow.com/2017/09/06/extreme-telescopes-find-the-second-fastest-spinning-pulsar/
Title: Re: Exoplanets And Stars Thread
Post by: hop on 09/08/2017 07:19 AM
A fun one: From what stars are we a transiting planet?

Transit Visibility Zones of the Solar System Planets (https://arxiv.org/abs/1709.02211) R. Wells, K. Poppenhaeger, C. A. Watson, R. Heller

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The detection of thousands of extrasolar planets by the transit method naturally raises the question of whether potential extrasolar observers could detect the transits of the Solar System planets. We present a comprehensive analysis of the regions in the sky from where transit events of the Solar System planets can be detected. We specify how many different Solar System planets can be observed from any given point in the sky, and find the maximum number to be three. We report the probabilities of a randomly positioned external observer to be able to observe single and multiple Solar System planet transits; specifically, we find a probability of 2.518% to be able to observe at least one transiting planet, 0.229% for at least two transiting planets, and 0.027% for three transiting planets. We identify 68 known exoplanets that have a favourable geometric perspective to allow transit detections in the Solar System and we show how the ongoing K2 mission will extend this list. We use occurrence rates of exoplanets to estimate that there are 3.2±1.2 and 6.6+1.3−0.8 temperate Earth-sized planets orbiting GK and M dwarf stars brighter than V=13 and V=16 respectively, that are located in the Earth's transit zone.
Title: Re: Exoplanets And Stars Thread
Post by: CuddlyRocket on 09/08/2017 11:00 PM
A System of Three Super Earths Transiting the Late K-Dwarf GJ 9827 at Thirty Parsecs (https://arxiv.org/abs/1709.01957) (arXiv)

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We report the discovery of three small transiting planets orbiting GJ 9827, a bright (K = 7.2) nearby late K-type dwarf star. GJ 9827 hosts a 1.64+0.22−0.20 R⊕ super Earth on a 1.2 day period, a 1.29+0.17−0.16 R⊕ super Earth on a 3.6 day period, and a 2.08+0.28−0.26 R⊕ super Earth on a 6.2 day period. The radii of the planets transiting GJ 9827 span the transition between predominantly rocky and gaseous planets, and GJ 9827 b and c fall in or close to the known gap in the radius distribution of small planets between these populations. At a distance of ∼30 parsecs, GJ 9827 is the closest exoplanet host discovered by K2 to date, making these planets well-suited for atmospheric studies with the upcoming James Webb Space Telescope. The GJ 9827 system provides a valuable opportunity to characterize interior structure and atmospheric properties of coeval planets spanning the rocky to gaseous transition.

The 'known gap' is the so-called Fulton Gap. I guess the name hasn't stuck with the wider astronomical community (yet?). :)
Title: Re: Exoplanets And Stars Thread
Post by: Star One on 09/11/2017 07:15 PM
Gravitational Waves will let us see Inside Stars as Supernovae Happen

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However, according to a team of astronomers from Glasgow and Arizona, astronomers need not limit themselves to detecting waves caused by massive gravitational mergers. According to a study they recently produced, the Advanced LIGO, GEO 600, and Virgo gravitational-wave detector network could also detect the gravitational waves created by supernova. In so doing, astronomers will able to see inside the hearts of collapsing stars for the first time.

The study, titled “Inferring the Core-Collapse Supernova Explosion Mechanism with Three-Dimensional Gravitational-Wave Simulations“, recently appeared online. Led by Jade Powell, who recently finished her PhD at the Institute for Gravitational Research at the University of Glasgow, the team argue that current gravitational wave experiments should be able to detect the waves created by Core Collapse Supernovae (CSNe).

https://www.universetoday.com/137068/gravitational-waves-will-let-us-see-inside-stars-supernovae-happen/amp/
Title: Re: Exoplanets And Stars Thread
Post by: redliox on 09/12/2017 12:06 AM
How large does a scope need to be to directly image one of the nearer exoplanets?

Let's assume we're targeting Epsilon Eridani's planet and the 'scope has a coronograph built in.  Anyone able to crunch the numbers?
Title: Re: Exoplanets And Stars Thread
Post by: jebbo on 09/12/2017 11:07 AM
How large does a scope need to be to directly image one of the nearer exoplanets?

Let's assume we're targeting Epsilon Eridani's planet and the 'scope has a coronograph built in.  Anyone able to crunch the numbers?

You really don't need that large a telescope (assuming space based).  The key things are the Inner Working Angle and contrast ratio between the star and planet.

For example, MAPLE-150 (1.5m) would be able to resolve epsilon Eridani b:

--- Tony
Title: Re: Exoplanets And Stars Thread
Post by: redliox on 09/12/2017 06:11 PM
How large does a scope need to be to directly image one of the nearer exoplanets?

Let's assume we're targeting Epsilon Eridani's planet and the 'scope has a coronograph built in.  Anyone able to crunch the numbers?

You really don't need that large a telescope (assuming space based).  The key things are the Inner Working Angle and contrast ratio between the star and planet.

For example, MAPLE-150 (1.5m) would be able to resolve epsilon Eridani b:

--- Tony

That's hopeful.  I believe I can understand what you mean by ratio (such as how a bright distant Jupiter might be easier to detect that a dark SuperEarth), but elaborate on IWA.  What else would allow an exoplanet to be more than a pixel in an image as well?
Title: Re: Exoplanets And Stars Thread
Post by: as58 on 09/12/2017 07:40 PM
How large does a scope need to be to directly image one of the nearer exoplanets?

Let's assume we're targeting Epsilon Eridani's planet and the 'scope has a coronograph built in.  Anyone able to crunch the numbers?

You really don't need that large a telescope (assuming space based).  The key things are the Inner Working Angle and contrast ratio between the star and planet.

For example, MAPLE-150 (1.5m) would be able to resolve epsilon Eridani b:

--- Tony

That's hopeful.  I believe I can understand what you mean by ratio (such as how a bright distant Jupiter might be easier to detect that a dark SuperEarth), but elaborate on IWA.  What else would allow an exoplanet to be more than a pixel in an image as well?

IWA is the smallest angle where at least 50% percent of the light is transmitted by the coronagraph; at smaller angles most of the light from the planet is blocked along with stellar light. Best coronagraph designs achieve IWA of about 2*lambda/D. But if you mean by "resolving" seeing the planet as something other than just a single pixel, much bigger telescopes are needed.
Title: Re: Exoplanets And Stars Thread
Post by: Star One on 09/13/2017 08:48 PM
Boiling exoplanet has titanium atmosphere

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The exoplanet WASP-19b has huge amounts of titanium oxide in its atmosphere, causing the atmosphere to 'reverse' so some of the upper layers are warmer than those lower down.

http://m.skyatnightmagazine.com/news/boiling-exoplanet-has-titanium-atmosphere
Title: Re: Exoplanets And Stars Thread
Post by: Star One on 09/15/2017 07:18 PM
NASA's Hubble Captures Blistering Pitch-Black Planet
NASA's Hubble Space Telescope has observed a planet outside our solar system that looks as black as fresh asphalt because it eats light rather than reflecting it back into space. This light-eating prowess is due to the planet's unique capability to trap at least 94 percent of the visible starlight falling into its atmosphere.

The oddball exoplanet, called WASP-12b, is one of a class of so-called "hot Jupiters," gigantic, gaseous planets that orbit very close to their host star and are heated to extreme temperatures. The planet's atmosphere is so hot that most molecules are unable to survive on the blistering day side of the planet, where the temperature is 4,600 degrees Fahrenheit. Therefore, clouds probably cannot form to reflect light back into space. Instead, incoming light penetrates deep into the planet's atmosphere where it is absorbed by hydrogen atoms and converted to heat energy.

"We did not expect to find such a dark exoplanet," said Taylor Bell of McGill University and the Institute for Research on Exoplanets in Montreal, Quebec, Canada, lead researcher of the Hubble study. "Most hot Jupiters reflect about 40 percent of starlight."

But the planet's nighttime side is a different story. WASP-12b has a fixed day side and night side because it orbits so close to the star that it is tidally locked. The nighttime side is more than 2,000 degrees Fahrenheit cooler, which allows water vapor and clouds to form. Previous Hubble observations of the day/night boundary detected evidence of water vapor and possibly clouds and hazes in the atmosphere. WASP-12b is about 2 million miles away from its star and completes an orbit once a day.

"This new Hubble research further demonstrates the vast diversity among the strange population of hot Jupiters," Bell said. "You can have planets like WASP-12b that are 4,600 degrees Fahrenheit and some that are 2,200 degrees Fahrenheit, and they're both called hot Jupiters. Past observations of hot Jupiters indicate that the temperature difference between the day and night sides of the planet increases with hotter day sides. This previous research suggests that more heat is being pumped into the day side of the planet, but the processes, such as winds, that carry the heat to the night side of the planet don't keep up the pace."

The researchers determined the planet's light-eating capabilities by using Hubble's Space Telescope Imaging Spectrograph to search in mostly visible light for a tiny dip in starlight as the planet passed directly behind the star. The amount of dimming tells astronomers how much reflected light is given off by the planet. However, the observations did not detect reflected light, meaning that the daytime side of the planet is absorbing almost all the starlight falling onto it.

First spotted in 2008, WASP-12b circles a Sun-like star residing 1,400 light-years away in the constellation Auriga. Since its discovery, several telescopes have studied the exoplanet, including Hubble, NASA's Spitzer Space Telescope, and NASA's Chandra X-ray Observatory. Previous observations by Hubble's Cosmic Origins Spectrograph (COS) revealed that the planet may be downsizing. COS detected material from the planet's super-heated atmosphere spilling onto the star.

The results appear in the Sept. 14 issue of The Astrophysical Journal Letters.

https://www.nasa.gov/feature/goddard/2017/hubble-captures-blistering-pitch-black-planet
Title: Re: Exoplanets And Stars Thread
Post by: CuddlyRocket on 09/15/2017 10:22 PM
Bayesian Analysis of Hot Jupiter Radius Anomalies: Evidence for Ohmic Dissipation? (https://arxiv.org/abs/1709.04539) (arXiv)

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The cause of hot Jupiter radius inflation, where giant planets with Teq >1000 K are significantly larger than expected, is an open question and the subject of many proposed explanations. Rather than examine these models individually, this work seeks to characterize the anomalous heating as a function of incident flux, ϵ(F), needed to inflate the population of planets to their observed sizes. We then compare that result to theoretical predictions for various models. We examine the population of about 300 giant planets with well-determined masses and radii and apply thermal evolution and Bayesian statistical models to infer the anomalous power as a function of incident flux that best reproduces the observed radii. First, we observe that the inflation of planets below about M=0.5MJ appears very different than their higher mass counterparts, perhaps as the result of mass loss or an inefficient heating mechanism. As such, we exclude planets below this threshold. Next, we show with strong significance that ϵ(F) increases with Teq towards a maximum of ∼2.5% at Teq≈1500 K, and then decreases as temperatures increase further, falling to ∼0.2% at Teff=2500 K. This high-flux decrease in inflation efficiency was predicted by the Ohmic dissipation model of giant planet inflation but not other models. We also explicitly check the thermal tides model and find that it predicts far more variance in radii than is observed. Thus, our results provide evidence for the Ohmic dissipation model and a functional form for ϵ(F) that any future theories of hot Jupiter radii can be tested against.

It's interesting that exoplanet studies are quickly finding these apparent physical boundaries separating planets into different classes.
Post by: Star One on 09/17/2017 07:05 PM
Diamonds Really Do Rain on Neptune, Experiments Conclude

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Researchers subjected hydrocarbon samples in a laboratory to Neptune-like pressures. The samples, reminiscent of molecules found in the ice giant’s atmosphere, compressed into nanodiamonds.

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Knowing how hydrocarbons might behave deep within an ice giant’s atmosphere will affect our understanding of how atmospheres transport heat and evolve over time, explained Kraus. What’s more, the implications of this research extend beyond our solar system to exoplanets, as a large fraction of the known exoplanets are similar in size or mass to our ice giants.

The ability to model an ice giant atmosphere’s density from the top down to the core is a critical part of characterizing that planet. For example, an atmosphere made mostly of hydrogen is much puffier than one with diamonds, Kraus noted.

A diamond-studded atmosphere also likely behaves very differently than one without diamonds. For example, atmospheric convection might have to overcome more hurdles, which may lead to sharp changes in chemical composition between different atmospheric layers, the researchers said. This could also inhibit heat flow.

“These experiments can be used to improve our understanding of the behavior of common materials in the universe at high pressures and temperatures, which has a direct connection to modeling planetary interiors,” said Ravit Helled, a computational science and theoretical astrophysics professor at the University of Zurich in Switzerland, who was not involved in the study.

https://eos.org/articles/diamonds-really-do-rain-on-neptune-experiments-conclude
Title: Re: Exoplanets And Stars Thread
Post by: Star One on 09/18/2017 08:04 PM
Do planets remember how they formed?

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One of the most directly observable features of a transiting multi-planet system is their size-ordering when ranked in orbital separation. Kepler has revealed a rich diversity of outcomes, from perfectly ordered systems, like Kepler-80, to ostensibly disordered systems, like Kepler-20. Under the hypothesis that systems are born via preferred formation pathways, one might reasonably expect non-random size-orderings reflecting these processes. However, subsequent dynamical evolution, often chaotic and turbulent in nature, may erode this information and so here we ask - do systems remember how they formed? To address this, we devise a model to define the entropy of a planetary system's size-ordering, by first comparing differences between neighboring planets and then extending to accommodate differences across the chain. We derive closed-form solutions for many of the micro state occupancies and provide public code with look-up tables to compute entropy for up to ten-planet systems. All three proposed entropy definitions exhibit the expected property that their credible interval increases with respect to a proxy for time. We find that the observed Kepler multis display a highly significant deficit in entropy compared to a randomly generated population. Incorporating a filter for systems deemed likely to be dynamically packed, we show that this result is robust against the possibility of missing planets too. Put together, our work establishes that Kepler systems do indeed remember something of their younger years and highlights the value of information theory for exoplanetary science.

https://arxiv.org/abs/1709.04987
Title: Re: Exoplanets And Stars Thread
Post by: Star One on 09/18/2017 08:30 PM
New supernova analysis reframes dark energy debate

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The accelerating expansion of the universe may not be real, but could just be an apparent effect, according to new research published in the journal Monthly Notices of the Royal Astronomical Society. The new study — by a group at the University of Canterbury in Christchurch, New Zealand — finds the fit of Type Ia supernovae to a model universe with no dark energy to be very slightly better than the fit to the standard dark energy model.

https://astronomynow.com/2017/09/18/new-supernova-analysis-reframes-dark-energy-debate/
Title: Re: Exoplanets And Stars Thread
Post by: Star One on 09/21/2017 04:03 PM
The empty primordial asteroid belt

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Abstract
The asteroid belt contains less than a thousandth of Earth’s mass and is radially segregated, with S-types dominating the inner belt and C-types the outer belt. It is generally assumed that the belt formed with far more mass and was later strongly depleted. We show that the present-day asteroid belt is consistent with having formed empty, without any planetesimals between Mars and Jupiter’s present-day orbits. This is consistent with models in which drifting dust is concentrated into an isolated annulus of terrestrial planetesimals. Gravitational scattering during terrestrial planet formation causes radial spreading, transporting planetesimals from inside 1 to 1.5 astronomical units out to the belt. Several times the total current mass in S-types is implanted, with a preference for the inner main belt. C-types are implanted from the outside, as the giant planets’ gas accretion destabilizes nearby planetesimals and injects a fraction into the asteroid belt, preferentially in the outer main belt. These implantation mechanisms are simple by-products of terrestrial and giant planet formation. The asteroid belt may thus represent a repository for planetary leftovers that accreted across the solar system but not in the belt itself.

Title: Re: Exoplanets And Stars Thread
Post by: Star One on 09/22/2017 09:22 AM

Astronomers Have Spotted a Strange Hybrid Asteroid in Our Solar System

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The Hubble space telescope has seen a lot of weird things that defy easy definition. Here's one more for the list – a binary asteroid that's also a comet.

Astronomers have found a pair of them, in fact, swirling around one another in the asteroid belt while leaving a stream of dust in their wake. Not only is it a beautiful example of how nature DNGAF about our categories, it raises some interesting questions on how many of these hybrids might be out there.

The binary object itself was first spotted back in 2006 as part of the asteroid-searching Spacewatch program, resulting in it getting the not-so-glamorous name 2006 VW139.

It wasn't until 2012 that astronomers realised something odd about it; this thing that was an asteroid with comet-like characteristics, namely a streaming tail.

So-called main belt comets aren't new, but they're by no means common either. This asteroid is just one of about a dozen such objects ever discovered.

What makes this particular one so unique is that it's in two pieces.

2006 VW139 is made of a pair of equal-sized lumps orbiting one another at a distance of just under 100 kilometres (about 60 miles).

Title: Re: Exoplanets And Stars Thread
Post by: Star One on 09/22/2017 04:46 PM
A Fast Radio Burst Occurs Every Second throughout the Observable Universe

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Abstract
Recent multi-telescope observations of the repeating fast radio burst (FRB) FRB 121102 reveal a Gaussian-like spectral profile and associate the event with a dwarf metal-poor galaxy at a cosmological redshift of 0.19. Assuming that this event represents the entire FRB population, we make predictions for the expected number counts of FRBs observable by future radio telescopes between 50 MHz and 3.5 GHz. We vary our model assumptions to bracket the expected rate of FRBs and find that it exceeds one FRB per second per sky when accounting for faint sources. We show that future low-frequency radio telescopes, such as the Square Kilometre Array, could detect more than one FRB per minute over the entire sky originating from the epoch of reionization.

http://iopscience.iop.org/article/10.3847/2041-8213/aa8905/meta
Title: Re: Exoplanets And Stars Thread
Post by: Star One on 09/25/2017 08:07 PM
Star nicknamed Kronos after eating its own planetary children

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A sun-like star seems to have devoured some of its own planetary offspring, prompting researchers to nickname it after the titan Kronos from Greek mythology.

The star HD 240430 is part of a binary system with HD 240429, and the two have now been nicknamed Kronos and Krios. The pair travel through the galaxy side by side some 320 light years from Earth.

They both seem to be about 4 billion years old, suggesting they were born from the same interstellar cloud, and initially shared the same chemical make-up.

But an analysis by Semyeong Oh at Princeton University and her team suggests the twins have led very different lives. Krios has noticeably smaller concentrations of elements like lithium, magnesium and iron floating in its atmosphere than its companion Kronos does.

In fact, the stars are more chemically different than any pair yet discovered. “I initially thought these two stars must not be in a binary,” says Oh.

https://www.newscientist.com/article/2148182-star-nicknamed-kronos-after-eating-its-own-planetary-children/
Title: Re: Exoplanets And Stars Thread
Post by: redliox on 09/26/2017 01:43 AM
Star nicknamed Kronos after eating its own planetary children

Quote
A sun-like star seems to have devoured some of its own planetary offspring, prompting researchers to nickname it after the titan Kronos from Greek mythology.

The star HD 240430 is part of a binary system with HD 240429, and the two have now been nicknamed Kronos and Krios. The pair travel through the galaxy side by side some 320 light years from Earth.

They both seem to be about 4 billion years old, suggesting they were born from the same interstellar cloud, and initially shared the same chemical make-up.

But an analysis by Semyeong Oh at Princeton University and her team suggests the twins have led very different lives. Krios has noticeably smaller concentrations of elements like lithium, magnesium and iron floating in its atmosphere than its companion Kronos does.

In fact, the stars are more chemically different than any pair yet discovered. “I initially thought these two stars must not be in a binary,” says Oh.

https://www.newscientist.com/article/2148182-star-nicknamed-kronos-after-eating-its-own-planetary-children/

Considering these theories are applicable to our own solar system's migrating planets, could there be a way to chemically discern how many planets the sun may have consumed in the past?
Title: Re: Exoplanets And Stars Thread
Post by: Star One on 09/26/2017 04:56 PM
Quote
Comparative exoplanetology? That’s the striking term that Angelos Tsiaras, lead author of a new paper on exoplanet atmospheres, uses to describe the field today. Kepler’s valuable statistical look at a crowded starfield has given us insights into the sheer range of outcomes around other stars, but we’re already moving into the next phase, studying planetary atmospheres. And as the Tsiaras paper shows, constructing the first atmospheric surveys.

Tsiaras (University College, London) assembled a team of European researchers that examined 30 exoplanets, constructing their spectral profiles and analyzing them to uncover the characteristic signatures of the gases present. The study found atmospheres around 16 ‘hot Jupiters,’ learning that water vapor was present in each of them. Says Tsiaras:

“More than 3,000 exoplanets have been discovered but, so far, we’ve studied their atmospheres largely on an individual, case-by-case basis. Here, we’ve developed tools to assess the significance of atmospheric detections in catalogues of exoplanets. This kind of consistent study is essential for understanding the global population and potential classifications of these foreign worlds.”

https://www.centauri-dreams.org/?p=38547
Title: Re: Exoplanets And Stars Thread
Post by: Star One on 09/27/2017 09:00 AM
Most Super-Earths Are Likely Not Habitable

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The tendency of planets to migrate early in a solar system’s history—like a planetary billiards game—would preclude the kind of stable environments that life needs to evolve. And a primitive, hydrogen-helium atmosphere would be very challenging for life. Exceptions to this general principle may still exist. For example, a planet’s original atmosphere can be lost due to radiation or impacts, as happened on Earth.

Even so, it seems that Earth’s mass is close to the optimum for a life-hosting planet. Given the new modeling results and insights, it also appears that most Super-Earths are likely not to be habitable. In the end, however, only observations will answer this question for certain. Fortunately, we should able to determine the atmospheric compositions of some Super-Earth planets within a decade.

Title: Re: Exoplanets And Stars Thread
Post by: Star One on 09/27/2017 07:10 PM
NEWLY DISCOVERED STAR CLUSTER ANALYZED BY GAIA PROBE

https://www.universetoday.com/137305/newly-discovered-star-cluster-analyzed-gaia-probe/

Paper:

https://arxiv.org/pdf/1709.04022.pdf
Title: Re: Exoplanets And Stars Thread
Post by: Star One on 09/30/2017 10:04 AM
NASA's Hubble Observes the Farthest Active Inbound Comet Yet Seen

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NASA's Hubble Space Telescope has photographed the farthest active inbound comet ever seen, at a whopping distance of 1.5 billion miles from the Sun (beyond Saturn's orbit). Slightly warmed by the remote Sun, it has already begun to develop an 80,000-mile-wide fuzzy cloud of dust, called a coma, enveloping a tiny, solid nucleus of frozen gas and dust. These observations represent the earliest signs of activity ever seen from a comet entering the solar system's planetary zone for the first time.

The comet, called C/2017 K2 (PANSTARRS) or "K2", has been travelling for millions of years from its home in the frigid outer reaches of the solar system, where the temperature is about minus 440 degrees Fahrenheit. The comet's orbit indicates that it came from the Oort Cloud, a spherical region almost a light-year in diameter and thought to contain hundreds of billions of comets. Comets are the icy leftovers from the formation of the solar system 4.6 billion years ago and therefore pristine in icy composition.

"K2 is so far from the Sun and so cold, we know for sure that the activity — all the fuzzy stuff making it look like a comet — is not produced, as in other comets, by the evaporation of water ice," said lead researcher David Jewitt of the University of California, Los Angeles. "Instead, we think the activity is due to the sublimation [a solid changing directly into a gas] of super-volatiles as K2 makes its maiden entry into the solar system's planetary zone. That's why it's special. This comet is so far away and so incredibly cold that water ice there is frozen like a rock."

Based on the Hubble observations of K2's coma, Jewitt suggests that sunlight is heating frozen volatile gases - such as oxygen, nitrogen, carbon dioxide, and carbon monoxide - that coat the comet's frigid surface. These icy volatiles lift off from the comet and release dust, forming the coma. Past studies of the composition of comets near the Sun have revealed the same mixture of volatile ices.

"I think these volatiles are spread all through K2, and in the beginning billions of years ago, they were probably all through every comet presently in the Oort Cloud," Jewitt said. "But the volatiles on the surface are the ones that absorb the heat from the Sun, so, in a sense, the comet is shedding its outer skin. Most comets are discovered much closer to the Sun, near Jupiter's orbit, so by the time we see them, these surface volatiles have already been baked off. That's why I think K2 is the most primitive comet we've seen."

K2 was discovered in May 2017 by the Panoramic Survey Telescope and Rapid Response System (Pan-STARRS) in Hawaii, a survey project of NASA's Near-Earth Object Observations Program. Jewitt used Hubble's Wide Field Camera 3 at the end of June to take a closer look at the icy visitor.

Hubble's sharp "eye" revealed the extent of the coma and also helped Jewitt estimate the size of the nucleus — less than 12 miles across — though the tenuous coma is 10 Earth diameters across.

This vast coma must have formed when the comet was even farther away from the Sun. Digging through archival images, Jewitt's team uncovered views of K2 and its fuzzy coma taken in 2013 by the Canada-France-Hawaii Telescope (CFHT) in Hawaii. But the object was then so faint that no one noticed it.

"We think the comet has been continuously active for at least four years," Jewitt said. "In the CFHT data, K2 had a coma already at 2 billion miles from the Sun, when it was between the orbits of Uranus and Neptune. It was already active, and I think it has been continuously active coming in. As it approaches the Sun, it's getting warmer and warmer, and the activity is ramping up."

But, curiously, the Hubble images do not show a tail flowing from K2, which is a signature of comets. The absence of such a feature indicates that particles lifting off the comet are too large for radiation pressure from the Sun to sweep them back into a tail.

Astronomers will have plenty of time to conduct detailed studies of K2. For the next five years, the comet will continue its journey into the inner solar system before it reaches its closest approach to the Sun in 2022 just beyond Mars' orbit. "We will be able to monitor for the first time the developing activity of a comet falling in from the Oort Cloud over an extraordinary range of distances," Jewitt said. "It should become more and more active as it nears the Sun and presumably will form a tail."

Jewitt said that NASA's James Webb Space Telescope, an infrared observatory scheduled to launch in 2018, could measure the heat from the nucleus, which would give astronomers a more accurate estimate of its size.

The team's results will appear in the September 28 issue of The Astrophysical Journal Letters.

http://hubblesite.org/news_release/news/2017-40
Title: Re: Exoplanets And Stars Thread
Post by: hop on 09/30/2017 10:01 PM
Paper the article above about C/2017 K2 (PANSTARRS) refers to
A Comet Active Beyond the Crystallization Zone  (https://arxiv.org/abs/1709.10079) David Jewitt, Man-To Hui, Max Mutchler, Harold Weaver, Jing Li, Jessica Agarwal

Quote
We present observations showing in-bound long-period comet We present observations showing in-bound long-period comet C/2017 K2 (PANSTARRS) to be active at record heliocentric distance. Nucleus temperatures are too low (60 K to 70 K) either for water ice to sublimate or for amorphous ice to crystallize, requiring another source for the observed activity. Using the Hubble Space Telescope we find a sharply-bounded, circularly symmetric dust coma 105 km in radius, with a total scattering cross section of ∼105 km2. The coma has a logarithmic surface brightness gradient -1 over much of its surface, indicating sustained, steady-state dust production. A lack of clear evidence for the action of solar radiation pressure suggests that the dust particles are large, with a mean size ≳ 0.1 mm. Using a coma convolution model, we find a limit to the apparent magnitude of the nucleus V> 25.2 (absolute magnitude H> 12.9). With assumed geometric albedo pV = 0.04, the limit to the nucleus circular equivalent radius is < 9 km. Pre-discovery observations from 2013 show that the comet was also active at 23.7 AU heliocentric distance. While neither water ice sublimation nor exothermic crystallization can account for the observed distant activity, the measured properties are consistent with activity driven by sublimating supervolatile ices such as CO2, CO, O2 and N2. Survival of supervolatiles at the nucleus surface is likely a result of the comet's recent arrival from the frigid Oort cloud. to be active at record heliocentric distance. Nucleus temperatures are too low (60 K to 70 K) either for water ice to sublimate or for amorphous ice to crystallize, requiring another source for the observed activity. Using the Hubble Space Telescope we find a sharply-bounded, circularly symmetric dust coma 105 km in radius, with a total scattering cross section of ∼105 km2. The coma has a logarithmic surface brightness gradient -1 over much of its surface, indicating sustained, steady-state dust production. A lack of clear evidence for the action of solar radiation pressure suggests that the dust particles are large, with a mean size ≳ 0.1 mm. Using a coma convolution model, we find a limit to the apparent magnitude of the nucleus V> 25.2 (absolute magnitude H> 12.9). With assumed geometric albedo pV = 0.04, the limit to the nucleus circular equivalent radius is < 9 km. Pre-discovery observations from 2013 show that the comet was also active at 23.7 AU heliocentric distance. While neither water ice sublimation nor exothermic crystallization can account for the observed distant activity, the measured properties are consistent with activity driven by sublimating supervolatile ices such as CO2, CO, O2 and N2. Survival of supervolatiles at the nucleus surface is likely a result of the comet's recent arrival from the frigid Oort cloud.
Title: Re: Exoplanets And Stars Thread
Post by: missinglink on 10/02/2017 03:04 AM
enveloping a tiny, solid nucleus of frozen gas and dust . . .  estimate the size of the nucleus — less than 12 miles across
Twelve miles! Not so tiny. That could really ruin someone's day if it hits. Why worry about asteroids when comets are faster, bigger . . . and currently unstoppable even by targeted nukes.
Title: Re: Exoplanets And Stars Thread
Post by: bolun on 10/03/2017 09:27 AM
BIOMARKER FOUND IN SPACE COMPLICATES SEARCH FOR LIFE ON EXOPLANETS

http://sci.esa.int/rosetta/59625-biomarker-found-in-space-complicates-search-for-life-on-exoplanets/

Quote
A molecule once thought to be a useful marker for life as we know it has been discovered around a young star and at a comet for the first time, suggesting these ingredients are inherited during the planet-forming phase.

The discovery of methyl chloride was made by the ground-based Atacama Large Millimeter/submillimeter Array (ALMA) in Chile, and by ESA's Rosetta spacecraft following Comet 67P/Churyumov-Gerasimenko. It is the simplest member of a class of molecules known as organohalogens, which contain halogens, such as chlorine or fluorine, bonded with carbon.

Methyl chloride is well known on Earth as being used in industry. It is also produced naturally by biological and geological activity: it is the most abundant organohalogen in Earth's atmosphere, with up to three megatonnes produced a year, primarily from biological processes.

As such, it had been identified as a possible 'biomarker' in the search for life at exoplanets. This has been called into question, however, now it is seen in environments not derived from living organisms, and instead as a raw ingredient from which planets could eventually form.

This is also the first time an organohalogen has been detected in space, indicating that halogen- and carbon-centred chemistries are more intertwined than previously thought.
Title: Re: Exoplanets And Stars Thread
Post by: CuddlyRocket on 10/08/2017 08:25 PM
Exterior Companions to Hot Jupiters Orbiting Cool Stars are Coplanar (https://arxiv.org/abs/1710.01737) (arXiv)
(Juliette C. Becker, Andrew Vanderburg, Fred C. Adams, Tali Khain, Marta Bryan)

Quote
The existence of hot Jupiters has challenged theories of planetary formation since the first extrasolar planets were detected. Giant planets are generally believed to form far from their host stars, where volatile materials like water exist in their solid phase, making it easier for giant planet cores to accumulate. Several mechanisms have been proposed to explain how giant planets can migrate inward from their birth sites to short-period orbits. One such mechanism, called Kozai-Lidov migration, requires the presence of distant companions in orbits inclined by more than ∼40 degrees with respect to the plane of the hot Jupiter's orbit. The high occurrence rate of wide companions in hot Jupiter systems lends support to this theory for migration. However, the exact orbital inclinations of these detected planetary and stellar companions is not known, so it is not clear whether the mutual inclination of these companions is large enough for the Kozai-Lidov process to operate. This paper shows that in systems orbiting cool stars with convective outer layers, the orbits of most wide planetary companions to hot Jupiters must be well aligned with the orbits of the hot Jupiters and the spins of the host stars. For a variety of possible distributions for the inclination of the companion, the width of the distribution must be less than ∼20 degrees to recreate the observations with good fidelity. As a result, the companion orbits are likely well-aligned with those of the hot Jupiters, and the Kozai-Lidov mechanism does not enforce migration in these systems.
Title: Re: Exoplanets And Stars Thread
Post by: Star One on 10/09/2017 04:41 PM
A 'Pale Green Dot': Why Proxima Centauri b May Have a Shiny Tint

Quote
A world orbiting the sun's closest stellar neighbor may have a shiny green tint to it — and not necessarily because it's covered in leafy plants.

Researchers have found a way to characterize potential auroras on the nearby exoplanet Proxima Centauri b and found that, if the planet sports oxygen in its atmosphere, the auroras may give the atmosphere a greenish cast.

"The northern and southern lights [on Proxima Centauri b] would be at least 100 times brighter than on Earth," Rodrigo Luger, a postdoctoral student at the University of Washington, who led the study of how the planet's auroras could be spotted from Earth, told Space.com by email. Luger said the auroras might be so bright as to be visible with very powerful telescopes. [Proxima b By the Numbers: Possibly Earth-Like World at the Next Star Over]

https://www.space.com/38397-proxima-centauri-planet-could-be-green.html
Title: Re: Exoplanets And Stars Thread
Post by: Star One on 10/09/2017 07:24 PM
Scientists Just Found Half of the Missing Matter in Our Universe

Quote
Two teams of astronomers have found a way to observe the presence of the missing matter connecting the galaxies in the universe. This discovery can improve our understanding of how galaxies were formed in the years following the Big Bang.

https://futurism.com/scientists-just-found-half-of-the-missing-matter-in-our-universe/
Title: Re: Exoplanets And Stars Thread
Post by: Star One on 10/10/2017 03:26 PM
Astronomers find a Neptune-sized exoplanet in a binary star system

Quote
Using NASA's prolonged Kepler mission, known as K2, astronomers have discovered a new Neptune-sized planet in a binary star system in the Hyades open cluster. The newly found exoworld, designated K2-nnnA b, is the first known Neptune-sized planet in a binary system within an open cluster. The finding was reported Sept. 29 in a paper published on the arXiv pre-print server.

K2-nnnA b was initially spotted during K2's Campaign 13, conducted between March 8 and May 27, 2017. During this campaign, a team of astronomers led by David R. Ciardi of the California Institute of Technology (Caltech) observed a binary system named EPIC 247589423 consisting of a K-dwarf star and a late M-dwarf companion. As a result, the researchers identified a transit signal in the light curve of the binary.

https://m.phys.org/news/2017-10-astronomers-neptune-sized-exoplanet-binary-star.html
Post by: Star One on 10/11/2017 07:40 PM
Distant dwarf planet near Pluto has a ring that no one expected

Quote
A ring has been found around Haumea, a world more than 2 billion kilometres beyond Pluto. The ring is the most distant ever seen in our solar system.

“This is a landmark discovery,” says Alan Stern at the Southwest Research Institute in Boulder, Colorado. “It’s very exciting.”

Until recently, the only known rings circled giant planets such as Saturn. In 2013, however, astronomers found two rings around Chariklo, an odd little rock about 250 kilometres across between the orbits of Saturn and Uranus. Chiron, one of Chariklo’s neighbours, may also have a ring.

Quote
Ortiz and Santos-Sanz also found that Haumea is slightly larger than once thought: at its widest, it is nearly the diameter of Pluto, the largest-known object orbiting the sun beyond Neptune. It is, however, only about 1025 kilometres across at its narrowest point, less than half Pluto’s diameter.

It is also much less dense than previously thought and has a make-up similar to Pluto’s. Both worlds are mostly rock, surrounded by water ice. And both are shiny, reflecting about half the light that strikes them.

https://www.newscientist.com/article/2150152-distant-dwarf-planet-near-pluto-has-a-ring-that-no-one-expected/amp/

More here.

http://www.iaa.es/en/news/haumea-most-peculiar-pluto-companions-has-ring-around-it
Title: Re: Exoplanets And Stars Thread
Post by: Star One on 10/17/2017 07:17 PM
How Bright is the Moon, Really?

Quote
The “inconstant moon,” as Shakespeare called it in Romeo and Juliet, is more reliable than his pair of star-crossed lovers might have thought. Now researchers at the National Institute of Standards and Technology (NIST) plan to make the Moon even more reliable with a new project to measure its brightness.
Scientists put the Moon to work daily as a calibration source for space-based cameras that use the brightness and colors of sunlight reflecting off our planet to track weather patterns, trends in crop health, the locations of harmful algal blooms in oceans and much more. The information sent from Earth-facing imagers allows researchers to predict famines and floods and can help communities plan emergency response and disaster relief.
To make sure that one satellite camera’s “green” isn’t another’s “yellow,” each camera is calibrated—in space—against a common source. The Moon makes a convenient target because, unlike Earth, it has no atmosphere and its surface changes very little.
The trouble is that, for all the songs written about the light of the silvery Moon, it’s still not understood exactly how bright the Moon’s reflected light is, at all times and from all angles. Today’s best measurements allow researchers to calculate the Moon’s brightness with uncertainties of a few percent—not quite good enough for the most sensitive measurement needs, says NIST’s Stephen Maxwell. To make up for these shortcomings, scientists have developed complicated workarounds. For example, they must periodically check the accuracy of their satellite images by making the same measurements multiple ways—from space, from the air and from the ground—simultaneously.
Or, if they want to compare images taken at different times by different satellites, they have to ensure that there is some overlap during their time in space so that the imagers have the chance to measure the same part of the planet at roughly the same time. But what happens if a research team can’t get a new camera into space before an old one is retired? “You get what’s called a data gap, and you lose the ability to stitch together measurements from different satellites to determine long-term trends,” Maxwell says.
Really knowing how bright the Moon is—with uncertainties of much less than 1 percent—would reduce the need for these logistically challenging solutions and ultimately save money.
So NIST is setting out to take new measurements of the Moon’s brightness. Researchers hope they will be the best measurements to date.

https://www.nist.gov/news-events/news/2017/10/how-bright-moon-really
Title: Re: Exoplanets And Stars Thread
Post by: JasonAW3 on 10/17/2017 08:17 PM
Distant dwarf planet near Pluto has a ring that no one expected

Quote
A ring has been found around Haumea, a world more than 2 billion kilometres beyond Pluto. The ring is the most distant ever seen in our solar system.

“This is a landmark discovery,” says Alan Stern at the Southwest Research Institute in Boulder, Colorado. “It’s very exciting.”

Until recently, the only known rings circled giant planets such as Saturn. In 2013, however, astronomers found two rings around Chariklo, an odd little rock about 250 kilometres across between the orbits of Saturn and Uranus. Chiron, one of Chariklo’s neighbours, may also have a ring.

Quote
Ortiz and Santos-Sanz also found that Haumea is slightly larger than once thought: at its widest, it is nearly the diameter of Pluto, the largest-known object orbiting the sun beyond Neptune. It is, however, only about 1025 kilometres across at its narrowest point, less than half Pluto’s diameter.

It is also much less dense than previously thought and has a make-up similar to Pluto’s. Both worlds are mostly rock, surrounded by water ice. And both are shiny, reflecting about half the light that strikes them.

https://www.newscientist.com/article/2150152-distant-dwarf-planet-near-pluto-has-a-ring-that-no-one-expected/amp/

More here.

http://www.iaa.es/en/news/haumea-most-peculiar-pluto-companions-has-ring-around-it

It occurs to me to wonder whether or not Huemea may be a fast rotating low density object.

It could be that the ring is ice that was flung off of the surface of Huemea, during it's "spin-up".  This could have been induced from a glancing strike by a high velocity object impacting its' surface at an angle.

Otherwise, it might have once been a spherical object, prior to the impact, even allowing for it's low density.
Title: Re: Exoplanets And Stars Thread
Post by: hop on 10/18/2017 03:38 AM
A follow up on the Teachey and Kipping exomoon candidate discussed earlier (http://forum.nasaspaceflight.com/index.php?topic=42108.msg1707055#msg1707055).

The nature of the giant exomoon candidate Kepler-1625 b-i (https://arxiv.org/abs/1710.06209) René Heller

(note, submitted not yet reviewed)

Quote
The recent announcement of a Neptune-sized exomoon candidate around the transiting Jupiter-sized object Kepler-1625 b could indicate the presence of a hitherto unknown kind of gas giant moons, if confirmed. Three transits have been observed, allowing radius estimates of both objects. Here we investigate possible mass regimes of the transiting system that could produce the observed signatures and study them in the context of moon formation in the solar system, i.e. via impacts, capture, or in-situ accretion. The radius of Kepler-1625 b suggests it could be anything from a gas giant planet somewhat more massive than Saturn (0.4 M_Jup) to a brown dwarf (BD) (up to 75 M_Jup) or even a very-low-mass star (VLMS) (112 M_Jup ~ 0.11 M_sun). The proposed companion would certainly have a planetary mass. Possible extreme scenarios range from a highly inflated Earth-mass gas satellite to an atmosphere-free water-rock companion of about 180 M_Ear. Furthermore, the planet-moon dynamics during the transits suggest a total system mass of 17.6_{-12.6}^{+19.2} M_Jup. A Neptune-mass exomoon around a giant planet or low-mass BD would not be compatible with the common mass scaling relation of the solar system moons about gas giants. The case of a mini-Neptune around a high-mass BD or a VLMS, however, would be located in a similar region of the satellite-to-host mass ratio diagram as Proxima b, the TRAPPIST-1 system, and LHS 1140 b. The capture of a Neptune-mass object around a 10 M_Jup planet during a close binary encounter is possible in principle. The ejected object, however, would have had to be a super-Earth object, raising further questions of how such a system could have formed. In summary, this exomoon candidate is barely compatible with established moon formation theories. If it can be validated as orbiting a super-Jovian planet, then it would pose an exquisite riddle for formation theorists to solve.
Title: Re: Exoplanets And Stars Thread
Post by: Star One on 10/20/2017 06:09 PM
NOPE, OUR TEMPORARY MOON ISN’T SPACE JUNK, IT’S AN ASTEROID

https://www.universetoday.com/137564/nope-temporary-moon-isnt-space-junk-asteroid/
Title: Re: Exoplanets And Stars Thread
Post by: Star One on 10/23/2017 05:05 PM
The proton and the antiproton are basically identical — indicating that maybe, the universe shouldn’t exist

https://www.zmescience.com/science/physics/proton-antimatter-magnetic-moment-23102017/
Title: Re: Exoplanets And Stars Thread
Post by: JasonAW3 on 10/23/2017 07:12 PM
The proton and the antiproton are basically identical — indicating that maybe, the universe shouldn’t exist

https://www.zmescience.com/science/physics/proton-antimatter-magnetic-moment-23102017/

Interesting question;  Is it possible that what we commonly refer to as "anti-matter" could exist as a non-baryonic form often referred to as Dark Matter?

If an equal mass of anti-matter were somehow "out of-phase", or more precisely, partially separated from this universe on a separate partial Brane, allowing the mass influences without the direct interaction of matter and anti-matter, would this not account for the absence of anti-matter, Dark Matter itself,  and part of the "missing mass" that appears absent in our universe?
Title: Re: Exoplanets And Stars Thread
Post by: Star One on 10/24/2017 03:41 PM
Spots On Supergiant Star Drive Spirals In Stellar Wind

https://scienmag.com/spots-on-supergiant-star-drive-spirals-in-stellar-wind/
Title: Re: Exoplanets And Stars Thread
Post by: Star One on 10/24/2017 07:25 PM
The nature of the giant exomoon candidate Kepler-1625 b-i

Quote
The recent announcement of a Neptune-sized exomoon candidate around the transiting Jupiter-sized object Kepler-1625 b could indicate the presence of a hitherto unknown kind of gas giant moons, if confirmed. Three transits have been observed, allowing radius estimates of both objects. Here we investigate possible mass regimes of the transiting system that could produce the observed signatures and study them in the context of moon formation in the solar system, i.e. via impacts, capture, or in-situ accretion. The radius of Kepler-1625 b suggests it could be anything from a gas giant planet somewhat more massive than Saturn (0.4 M_Jup) to a brown dwarf (BD) (up to 75 M_Jup) or even a very-low-mass star (VLMS) (112 M_Jup ~ 0.11 M_sun). The proposed companion would certainly have a planetary mass. Possible extreme scenarios range from a highly inflated Earth-mass gas satellite to an atmosphere-free water-rock companion of about 180 M_Ear. Furthermore, the planet-moon dynamics during the transits suggest a total system mass of 17.6_{-12.6}^{+19.2} M_Jup. A Neptune-mass exomoon around a giant planet or low-mass BD would not be compatible with the common mass scaling relation of the solar system moons about gas giants. The case of a mini-Neptune around a high-mass BD or a VLMS, however, would be located in a similar region of the satellite-to-host mass ratio diagram as Proxima b, the TRAPPIST-1 system, and LHS 1140 b. The capture of a Neptune-mass object around a 10 M_Jup planet during a close binary encounter is possible in principle. The ejected object, however, would have had to be a super-Earth object, raising further questions of how such a system could have formed. In summary, this exomoon candidate is barely compatible with established moon formation theories. If it can be validated as orbiting a super-Jovian planet, then it would pose an exquisite riddle for formation theorists to solve.

https://arxiv.org/abs/1710.06209
Title: Re: Exoplanets And Stars Thread
Post by: Star One on 10/25/2017 07:31 PM
New article.

Project Blue and the quest to photograph exoplanets

https://phys.org/news/2017-10-blue-quest-exoplanets.amp
Post by: Star One on 10/26/2017 07:24 PM
Astronomers discover sunscreen snow falling on hot exoplanet

Quote
Astronomers at Penn State have used the Hubble Space Telescope to find a blistering-hot giant planet outside our solar system where the atmosphere "snows" titanium dioxide -- the active ingredient in sunscreen. These Hubble observations are the first detections of this "snow-out" process, called a "cold trap," on an exoplanet. This discovery, and other observations made by the Penn State team, provide insight into the complexity of weather and atmospheric composition on exoplanets, and may someday be useful for gauging the habitability of Earth-size planets.

http://science.psu.edu/news-and-events/2017-news/Beatty10-2017
Post by: Star One on 10/31/2017 04:46 PM
Scientists detect comets outside our solar system

Quote
Scientists from MIT and other institutions, working closely with amateur astronomers, have spotted the dusty tails of six exocomets — comets outside our solar system — orbiting a faint star 800 light years from Earth.
These cosmic balls of ice and dust, which were about the size of Halley’s Comet and traveled about 100,000 miles per hour before they ultimately vaporized, are some of the smallest objects yet found outside our own solar system.
The discovery marks the first time that an object as small as a comet has been detected using transit photometry, a technique by which astronomers observe a star’s light for telltale dips in intensity. Such dips signal potential transits, or crossings of planets or other objects in front of a star, which momentarily block a small fraction of its light.
In the case of this new detection, the researchers were able to pick out the comet’s tail, or trail of gas and dust, which blocked about one-tenth of 1 percent of the star’s light as the comet streaked by.

http://news.mit.edu/2017/scientists-detect-comets-outside-our-solar-system-1026

We may have found 20 habitable worlds hiding in plain sight

Quote
There could be more habitable planets out there than we thought. An analysis of data from the Kepler space telescope has revealed 20 promising worlds that might be able to host life.

The list of potential worlds includes several planets that orbit stars like our sun. Some take a relatively long time to complete a single orbit, with the longest taking 395 Earth days and others taking Earth weeks or months. The fastest orbit is 18 Earth days. This is very different to the very short “years” we see around smaller stars with habitable planets like Proxima Centauri.

The exoplanet with a 395-day year is one of the most promising worlds for life on the list, says Jeff Coughlin, a Kepler team lead who helped find the potential planets. Called KOI-7923.01, it is 97 per cent the size of Earth, but a little colder.

Its cooler temperature is due to its distance from its star and the fact that the star is slightly cooler than our sun. This means it may be a little more like tundra regions on Earth than temperate ones, but is still warm enough and large enough to hold the liquid water essential to life as we know it.

“If you had to choose one to send a spacecraft to, it’s not a bad option,” says Coughlin.

A solid chance
The team is 70 to 80 per cent certain that these are solid candidates, he says. They can’t be confirmed yet as more observations are needed: the planets all come from the original Kepler mission, which stared at the same region of the sky for only four years before its aiming ability was crippled when its reaction wheels broke in 2013. This means that we have only seen each of these planets once or twice due to their long orbits, and the signals could be a little wobbly.

Ground-based observatories or the Hubble Space Telescope will have to take more observations over the coming years to double-check, Coughlin says.

https://www.newscientist.com/article/may-found-20-habitable-worlds-hiding-plain-sight/

Here’s the paper.

https://arxiv.org/abs/1710.06758
Title: Re: Exoplanets And Stars Thread
Post by: Star One on 10/31/2017 07:59 PM
Exoplanet-Hunting Survey Discovers Three More Giant Alien Worlds!

Quote
From the SuperWASP survey data, Dr. Demangeon and her colleagues were able to detect three transit signals coming from three distant stars – WASP-151, WASP-153 and WASP-156. This was then followed by spectroscopic observations performed using the Haute-Provence Observatory in France and the La Silla Observatory in Chile, which allowed the team to confirm the nature of these planets.

From this, they determined that WASP-151b and WASP-153b are two “hot Saturns”, meaning they are low-density gas giants with close orbits. They orbit their respective suns, which are both early G-type stars (aka. yellow dwarfs, like our Sun), with an orbital period of 4.53 and 3.33 days. WASP-156b, meanwhile, is a Super-Neptune that orbits a K-type (orange dwarf) star.

Quote
Taken together, these planets represent some major opportunities for exoplanet research. As they indicate, “these three planets also lie close to (WASP-151b and WASP-153b) or below (WASP-156b) the upper boundary of the Neptunian desert.” This refers to the boundary astronomers have observed around stars where shot period Neptune-size planets are very unlikely to be found.

Quote
The team also offered some possible explanations for the existence of a “Neptunian desert” based on their findings. For starters, they proposed that a high-eccentricity migration could be responsible, where Neptune-sized ice giants form in the outer reaches of a star system and migrate inward over time. They also indicate that their discovery offers compelling evidence that ultra-violet radiation and gas envelope-depletion could be a key part of the puzzle.

https://www.universetoday.com/137671/exoplanet-hunting-survey-discovers-three-giant-alien-worlds/amp/
Title: Re: Exoplanets And Stars Thread
Post by: jebbo on 11/01/2017 06:40 AM
First planet for the "Next Generation Transit Survey" programme.

Quote
We present the discovery of NGTS-1b, a hot-Jupiter transiting an early M-dwarf host (Teff=3916+71−63 K) in a P=2.674d orbit discovered as part of the Next Generation Transit Survey (NGTS). The planet has a mass of 0.812+0.066−0.075 MJ, making it the most massive planet ever discovered transiting an M-dwarf. The radius of the planet is 1.33+0.61−0.33 RJ. Since the transit is grazing, we determine this radius by modelling the data and placing a prior on the density from the population of known gas giant planets. NGTS-1b is the third transiting giant planet found around an M-dwarf, reinforcing the notion that close-in gas giants can form and migrate similar to the known population of hot Jupiters around solar type stars. The host star shows no signs of activity, and the kinematics hint at the star being from the thick disk population. With a deep (2.5%) transit around a K=11.9 host, NGTS-1b will be a strong candidate to probe giant planet composition around M-dwarfs via JWST transmission spectroscopy.

https://arxiv.org/abs/1710.11099 (https://arxiv.org/abs/1710.11099)
https://arxiv.org/abs/1710.11100 (https://arxiv.org/abs/1710.11100)

Edit: worth noting that this planet puts the cat slightly amongst the planet-formation pigeons as planets this large were not expected around such small stars.

--- Tony
Post by: Star One on 11/01/2017 11:56 AM
First planet for the "Next Generation Transit Survey" programme.

Quote
We present the discovery of NGTS-1b, a hot-Jupiter transiting an early M-dwarf host (Teff=3916+71−63 K) in a P=2.674d orbit discovered as part of the Next Generation Transit Survey (NGTS). The planet has a mass of 0.812+0.066−0.075 MJ, making it the most massive planet ever discovered transiting an M-dwarf. The radius of the planet is 1.33+0.61−0.33 RJ. Since the transit is grazing, we determine this radius by modelling the data and placing a prior on the density from the population of known gas giant planets. NGTS-1b is the third transiting giant planet found around an M-dwarf, reinforcing the notion that close-in gas giants can form and migrate similar to the known population of hot Jupiters around solar type stars. The host star shows no signs of activity, and the kinematics hint at the star being from the thick disk population. With a deep (2.5%) transit around a K=11.9 host, NGTS-1b will be a strong candidate to probe giant planet composition around M-dwarfs via JWST transmission spectroscopy.

https://arxiv.org/abs/1710.11099 (https://arxiv.org/abs/1710.11099)
https://arxiv.org/abs/1710.11100 (https://arxiv.org/abs/1710.11100)

Edit: worth noting that this planet puts the cat slightly amongst the planet-formation pigeons as planets this large were not expected around such small stars.

--- Tony

Wouldn’t one answer by that this was a wandering planet that was captured by this star?
Title: Re: Exoplanets And Stars Thread
Post by: CuddlyRocket on 11/01/2017 11:05 PM
Edit: worth noting that this planet puts the cat slightly amongst the planet-formation pigeons as planets this large were not expected around such small stars.

Wouldn’t one answer by that this was a wandering planet that was captured by this star?

It is an answer, but an extremely unlikely one. Not only would such a rogue planet have to come sufficiently near the star - and space is big compared to stars - but capture is not a straightforward process (generally there needs to be a third body of comparable size involved).

An alternative explanation is that this object was formed at the same time as its host star by direct collapse of the nebula - i.e. it's a very small brown dwarf (sub-brown dwarf?). I'm not sure if there are any theoretical minimums for the mass of objects formed by such a mechanism!
Title: Re: Exoplanets And Stars Thread
Post by: Star One on 11/02/2017 10:44 AM
Edit: worth noting that this planet puts the cat slightly amongst the planet-formation pigeons as planets this large were not expected around such small stars.

Wouldn’t one answer by that this was a wandering planet that was captured by this star?

It is an answer, but an extremely unlikely one. Not only would such a rogue planet have to come sufficiently near the star - and space is big compared to stars - but capture is not a straightforward process (generally there needs to be a third body of comparable size involved).

An alternative explanation is that this object was formed at the same time as its host star by direct collapse of the nebula - i.e. it's a very small brown dwarf (sub-brown dwarf?). I'm not sure if there are any theoretical minimums for the mass of objects formed by such a mechanism!

The mass estimates put below the minimum for a Brown Dwarf.
Title: Re: Exoplanets And Stars Thread
Post by: clongton on 11/02/2017 03:42 PM
Edit: worth noting that this planet puts the cat slightly amongst the planet-formation pigeons as planets this large were not expected around such small stars.

Wouldn’t one answer by that this was a wandering planet that was captured by this star?

It is an answer, but an extremely unlikely one. Not only would such a rogue planet have to come sufficiently near the star - and space is big compared to stars - but capture is not a straightforward process (generally there needs to be a third body of comparable size involved).

An alternative explanation is that this object was formed at the same time as its host star by direct collapse of the nebula - i.e. it's a very small brown dwarf (sub-brown dwarf?). I'm not sure if there are any theoretical minimums for the mass of objects formed by such a mechanism!

The mass estimates put below the minimum for a Brown Dwarf.

The minimum is a yet unproven theorem that may or may not be correct. The more we learn the faster our precious theorems fall by the wayside. It may ultimately prove to be correct but it will be a long, long time before that can occur. Best not to dismiss an idea based on unproven theorems.
Title: Re: Exoplanets And Stars Thread
Post by: jebbo on 11/02/2017 06:01 PM
For a bit of fun, follow the #ExoCup tag on Twitter ... interesting to see the advocacy for people's favourite exoplanets.

And it is actually fun!

--- Tony
Title: Re: Exoplanets And Stars Thread
Post by: Star One on 11/03/2017 04:36 PM
ALMA Discovery of Dust Belts Around Proxima Centauri

Quote
Proxima Centauri, the star closest to our Sun, is known to host at least one terrestrial planet candidate in a temperate orbit. Here we report the ALMA detection of the star at 1.3 mm wavelength and the discovery of a belt of dust orbiting around it at distances ranging between 1 and 4 au, approximately. Given the low luminosity of the Proxima Centauri star, we estimate a characteristic temperature of about 40 K for this dust, which might constitute the dust component of a small-scale analog to our solar system Kuiper belt. The estimated total mass, including dust and bodies up to 50 km in size, is of the order of 0.01 Earth masses, which is similar to that of the solar Kuiper belt. Our data also show a hint of warmer dust closer to the star. We also find signs of two additional features that might be associated with the Proxima Centauri system, which, however, still require further observations to be confirmed: an outer extremely cold (about 10 K) belt around the star at about 30 au, whose orbital plane is tilted about 45 degrees with respect to the plane of the sky; and additionally, we marginally detect a compact 1.3 mm emission source at a projected distance of about 1.2 arcsec from the star, whose nature is still unknown.

https://arxiv.org/abs/1711.00578
Title: Re: Exoplanets And Stars Thread
Post by: CuddlyRocket on 11/03/2017 10:59 PM
An alternative explanation is that this object was formed at the same time as its host star by direct collapse of the nebula - i.e. it's a very small brown dwarf (sub-brown dwarf?). I'm not sure if there are any theoretical minimums for the mass of objects formed by such a mechanism!

The mass estimates put below the minimum for a Brown Dwarf.

The minimum is a yet unproven theorem that may or may not be correct. The more we learn the faster our precious theorems fall by the wayside. It may ultimately prove to be correct but it will be a long, long time before that can occur. Best not to dismiss an idea based on unproven theorems.

The definition of a brown dwarf appears to still be subject to debate. Some define it as a sub-stellar object that is massive enough (>~13Mj) to undergo deuterium fusion. On that definition, this object is not a brown dwarf. Others define it as a sub-stellar object that was formed by the collapse of a nebula. I'm not aware of the minimum size of such objects (if any, though gas pressure presumably would overcome gravitational forces at some point?). By that definition this could be a brown dwarf. Given the definitional conflict I tentatively suggested the term 'sub-brown dwarf'! :)

ALMA Discovery of Dust Belts Around Proxima Centauri

I found the tentative possibility of a Saturn analogue (rings and all) to be the most interesting aspect:

Quote
Finally, an exciting alternative scenario is that the source traces a ring of dust surrounding an as yet undiscovered giant planet orbiting at a (projected) distance of 1.6 au (orbital period >~5.8 yr). ... we would expect a planet of mass ∼100 M⊕, the mass of Saturn, to account for the observed 1.3 mm emission. No clear RV signal that would indicate such a planet is present in the data of the long-term monitoring of the star. Further observations are being undertaken to confirm, or rule out this intriguing possibility. At any rate, our study shows that ALMA provides already the necessary sensitivity and resolution to detect rings around exoplanets in alpha Centauri, and perhaps in other nearby stars.
Post by: Star One on 11/03/2017 11:01 PM
An alternative explanation is that this object was formed at the same time as its host star by direct collapse of the nebula - i.e. it's a very small brown dwarf (sub-brown dwarf?). I'm not sure if there are any theoretical minimums for the mass of objects formed by such a mechanism!

The mass estimates put below the minimum for a Brown Dwarf.

The minimum is a yet unproven theorem that may or may not be correct. The more we learn the faster our precious theorems fall by the wayside. It may ultimately prove to be correct but it will be a long, long time before that can occur. Best not to dismiss an idea based on unproven theorems.

The definition of a brown dwarf appears to still be subject to debate. Some define it as a sub-stellar object that is massive enough (>~13Mj) to undergo deuterium fusion. On that definition, this object is not a brown dwarf. Others define it as a sub-stellar object that was formed by the collapse of a nebula. I'm not aware of the minimum size of such objects (if any, though gas pressure presumably would overcome gravitational forces at some point?). By that definition this could be a brown dwarf. Given the definitional conflict I tentatively suggested the term 'sub-brown dwarf'!

ALMA Discovery of Dust Belts Around Proxima Centauri

I found the tentative possibility of a Saturn analogue (rings and all) to be the most interesting aspect:

Quote
Finally, an exciting alternative scenario is that the source traces a ring of dust surrounding an as yet undiscovered giant planet orbiting at a (projected) distance of 1.6 au (orbital period >~5.8 yr). ... we would expect a planet of mass ∼100 M⊕, the mass of Saturn, to account for the observed 1.3 mm emission. No clear RV signal that would indicate such a planet is present in the data of the long-term monitoring of the star. Further observations are being undertaken to confirm, or rule out this intriguing possibility. At any rate, our study shows that ALMA provides already the necessary sensitivity and resolution to detect rings around exoplanets in alpha Centauri, and perhaps in other nearby stars.

If it is anywhere near as big as Saturn that’s another small star with an extremely big planet.

This link posted in the Red Dot thread seems to suggest it isn’t a gas giant.

http://www.astronomy.com/news/2017/11/proxima-rings
Title: Re: Exoplanets And Stars Thread
Post by: Alpha_Centauri on 11/03/2017 11:11 PM
Except the current RV surveys even before the most recent observations have already ruled out such a massive planet at this distance.
Title: Re: Exoplanets And Stars Thread
Post by: Bynaus on 11/04/2017 04:24 PM
The mass of the planet has only been guestimated from a ring-mass-to-planet-mass ratio of 1e-7. Whether it really is a ring, or whether planets with larger mass ratios exist are open questions.

"More work is necessary".
Title: Re: Exoplanets And Stars Thread
Post by: CuddlyRocket on 11/04/2017 07:05 PM
Except the current RV surveys even before the most recent observations have already ruled out such a massive planet at this distance.

Quoting from the paper:
Quote
No clear RV signal that would indicate such a planet is present in the data of the long-term monitoring of the star. Further observations are being undertaken to confirm, or rule out this intriguing possibility.

So, according to them, it's still an open question.
Title: Re: Exoplanets And Stars Thread
Post by: Dao Angkan on 11/06/2017 06:03 PM
Edit: worth noting that this planet puts the cat slightly amongst the planet-formation pigeons as planets this large were not expected around such small stars.

Wouldn’t one answer by that this was a wandering planet that was captured by this star?

It is an answer, but an extremely unlikely one. Not only would such a rogue planet have to come sufficiently near the star - and space is big compared to stars - but capture is not a straightforward process (generally there needs to be a third body of comparable size involved).

An alternative explanation is that this object was formed at the same time as its host star by direct collapse of the nebula - i.e. it's a very small brown dwarf (sub-brown dwarf?). I'm not sure if there are any theoretical minimums for the mass of objects formed by such a mechanism!

According to Shiv S. Kumar (who first theorised Brown Dwarfs in the 1960s) the theoretical minimum mass from cloud collapse is supposedly ~1 MJup, which is close to the mass range for this body (although slightly higher). Incidentally, the theoretical maximum mass from core accretion  in the vicinity of a star of any mass is supposedly ~2 MJup, presumably lower for low mass stars. This object is pretty close to the ~1 MJup limit, so may just be massive enough to have formed by cloud collapse.

The Bottom of the Main Sequence and Beyond: Speculations, Calculations, Observations, and Discoveries (1958-2002) (https://www.cambridge.org/core/services/aop-cambridge-core/content/view/01E697652BC3A1F68E814D1EBF8A6D85/S0074180900210176a.pdf/bottom_of_the_main_sequence_and_beyond_speculations_calculations_observations_and_discoveries_19582002.pdf)

Quote
The Basic Nature of the Stars and Planets

Since  1964,  I  have been presenting arguments to  show that the star formation processes are fundamentally different from those of planet formation (Kumar 1964; Kumar 1967; Kumar 1972a; Kumar 1974; Kumar 1990; Kumar 1995; Kumar 2000a). Stars (including brown dwarfs) are formed by the fragmentation of gaseous clouds, and the mass range in the stellar domain ranges from  a  few hundred solar masses to ~0.001 M☉ (or  ~1 MJup). Planets are formed by the slow accumulation (accretion) of dust, rocks, and gas  in the vicinity of  a star, and the mass range in the planetary domain ranges from ~0.000001 MJup to  ~2 MJup. Thus, as  far  as the masses of the stars and planets are concerned, I'm not talking of just one linear sequence but of  two separate sequences arising from two different formation processes.

The old idea that the stars and planets represent two sections of the same linear sequence (in mass), with objects above a certain mass labeled as stars and objects below that certain mass labeled as planets, is not the correct way  to understand the two groups of objects. The mass of  an object doesn't uniquely determine its basic nature. In order to ascertain the basic nature of an object, we have  to  know its formation mechanism. Theoretically speaking, an object of  1MJup (located somewhere in the Universe) may come into existence by either the star formation processes or the planet formation processes. As I have repeatedly pointed out (Kumar 1972a; Kumar 1974; Kumar 1994; Kumar 1995), the most massive planet in the Solar System (Jupiter) was most probably formed by the planet formation processes and not by the star formation processes. For Jupiter, the presence of  a rocky/metallic core, the chemical composition of its interior, and the chemical compositin of its atmosphere clearly indicate that the planet acquired its present mass  (in the presence of the Sun)  by the slow accretion of dust, rocks, and gas  over the past 4.5  billion years (Kumar 1994; Kumar 1995; Kumar 2000a).  It  does not appear to have been formed by the rapid collapse of an extended, gaseous object of mass  0.001 M☉.
Title: Re: Exoplanets And Stars Thread
Post by: Star One on 11/06/2017 07:15 PM
NuSTAR probes black hole mystery

Quote
Black holes are famous for being ravenous eaters, but they do not eat everything that falls toward them. A small portion of material gets shot back out in powerful jets of hot gas, called plasma, that can wreak havoc on their surroundings. Along the way, this plasma somehow gets energized enough to strongly radiate light, forming two bright columns along the black hole’s axis of rotation. Scientists have long debated where and how this happens in the jet.

Astronomers have new clues to this mystery. Using NASA’s NuSTAR space telescope and a fast camera called ULTRACAM on the William Herschel Observatory in La Palma, Spain, scientists have been able to measure the distance that particles in jets travel before they “turn on” and become bright sources of light. This distance is called the “acceleration zone.” The study is published in the journal Nature Astronomy.

https://astronomynow.com/2017/11/05/nustar-probes-black-hole-mystery/
Title: Re: Exoplanets And Stars Thread
Post by: Star One on 11/07/2017 08:17 PM
Alma’s image of red giant star gives a surprising glimpse of the Sun’s future

Quote
A Chalmers-led team of astronomers has for the first time observed details on the surface of an aging star with the same mass as the Sun. ALMA:s images show that the star is a giant, its diameter twice the size of Earth’s orbit around the Sun, but also that the star’s atmosphere is affected by powerful, unexpected shock waves. The research is published in Nature Astronomy on 30 October 2017.

http://www.chalmers.se/en/researchinfrastructure/oso/news/Pages/Alma-image-of-red-giant-star-gives-a-surprising-glimpse-of-the-Suns-future.aspx
Title: Re: Exoplanets And Stars Thread
Post by: Star One on 11/08/2017 07:48 PM
MSU biologists have found out how long can microorganisms live on Mars

Quote
"The results of the study indicate the possibility of prolonged cryoconservation of viable microorganisms in the Martian regolith. The intensity of ionizing radiation on the surface of Mars is 0.05-0.076 Gy/year and decreases with depth. Taking into account the intensity of radiation in the Mars regolith, the data obtained by us makes it possible to assume that hypothetical Mars ecosystems could be conserved in anabiotic state in the surface layer of regolith (protected from UV rays) for at least 1.3-2 million years, at a depth of two meters for no less than 3.3 million years, and at a depth of five meters for at least 20 million years. The data obtained can also be applied to assess the possibility of detecting viable microorganisms at other objects of the Solar System and within small bodies in outer space" - the scientist added.

The authors have for the first time proven that prokaryotes can survive irradiation with ionizing radiation in doses exceeding 80 kGy. The data obtained indicate both a possible underestimation of the radiation resistance of natural microbial communities and the need to study the joint effect of a set of extraterrestrial and cosmic factors on living organisms and biomolecules in astrobiological model experiments.

Post by: Star One on 11/10/2017 06:36 AM
OGLE-2016-BLG-1190Lb: First Spitzer Bulge Planet Lies Near the Planet/Brown-Dwarf Boundary

Quote
We report the discovery of OGLE-2016-BLG-1190Lb, which is likely to be the first Spitzer microlensing planet in the Galactic bulge/bar, an assignation that can be confirmed by two epochs of high-resolution imaging of the combined source-lens baseline object. The planet's mass M_p= 13.4+-0.9 M_J places it right at the deuterium burning limit, i.e., the conventional boundary between "planets" and "brown dwarfs". Its existence raises the question of whether such objects are really "planets" (formed within the disks of their hosts) or "failed stars" (low mass objects formed by gas fragmentation). This question may ultimately be addressed by comparing disk and bulge/bar planets, which is a goal of the Spitzer microlens program. The host is a G dwarf M_host = 0.89+-0.07 M_sun and the planet has a semi-major axis a~2.0 AU. We use Kepler K2 Campaign 9 microlensing data to break the lens-mass degeneracy that generically impacts parallax solutions from Earth-Spitzer observations alone, which is the first successful application of this approach. The microlensing data, derived primarily from near-continuous, ultra-dense survey observations from OGLE, MOA, and three KMTNet telescopes, contain more orbital information than for any previous microlensing planet, but not quite enough to accurately specify the full orbit. However, these data do permit the first rigorous test of microlensing orbital-motion measurements, which are typically derived from data taken over <1% of an orbital period.

https://arxiv.org/abs/1710.09974
Post by: Star One on 11/15/2017 05:04 PM
Ross 128 b: A ‘Temperate’ Planet?

Quote
What gives the Ross 128 b detection a wrinkle of astrobiological interest is that the star the planet orbits is relatively inactive. Red dwarfs are known for the flares that can flood nearby planets with ultraviolet and X-ray radiation. Compounded with the fact that habitable zone planets must orbit quite close to a parent M-dwarf (given the star’s small size and low temperature compared to the Sun), such flares could act as a brake on the development of life.

Ross 128 b may thus have a higher likelihood for astrobiological activity than Proxima b, assuming that it actually is in the habitable zone. Right now the team behind this work, led by Xavier Bonfils (Université Grenoble Alpes) hedges its bets by referring to the planet as ‘temperate’ and ‘close to the inner edge of the conventional habitable zone.’

https://www.centauri-dreams.org/?p=38800
Post by: CuddlyRocket on 11/16/2017 05:16 AM
Ross 128 b: A ‘Temperate’ Planet?

You can find the paper at A temperate exo-Earth around a quiet M dwarf at 3.4 parsecs (https://www.eso.org/public/archives/releases/sciencepapers/eso1736/eso1736a.pdf)

Quote
(from the abstract) Here we report on our radial velocity observations of Ross 128 (Proxima Virginis, GJ447, HIP 57548), an M4 dwarf just 3.4 parsec away from our Sun. This source hosts an exo-Earth with a projected mass m sin i = 1.35M⊕ and an orbital period of 9.9 days. Ross 128 b receives ∼1.38 times as much flux as Earth from the Sun and its equilibrium ranges in temperature between 269 K for an Earth-like albedo and 213 K for a Venus-like albedo. Recent studies place it close to the inner edge of the conventional habitable zone. An 80-day long light curve from K2 campaign C01 demonstrates that Ross 128 b does not transit. Together with the All Sky Automated Survey (ASAS) photometry and spectroscopic activity indices, the K2 photometry shows that Ross 128 rotates slowly and has weak magnetic activity. In a habitability context, this makes survival of its atmosphere against erosion more likely. Ross 128 b is the second closest known exo-Earth, after Proxima Centauri b (1.3 parsec), and the closest temperate planet known around a quiet star.

Interesting the use of the Kepler K2 data. Not gone unnoticed by the latter :) :

NASA's Kepler/K2 GO Office‏ @KeplerGO
8 hours ago
Did you know?  @NASAKepler observed #Ross128b in 2014!  The discovery paper uses these Kepler data to show that the planet does not transit, and that the host star is magnetically quiet and rotating slowly.  @ESO's #HARPS and @NASA's #K2Mission are a winning combo!
Post by: Star One on 11/16/2017 05:51 AM
Ross 128 b: A ‘Temperate’ Planet?

You can find the paper at A temperate exo-Earth around a quiet M dwarf at 3.4 parsecs (https://www.eso.org/public/archives/releases/sciencepapers/eso1736/eso1736a.pdf)

Quote
(from the abstract) Here we report on our radial velocity observations of Ross 128 (Proxima Virginis, GJ447, HIP 57548), an M4 dwarf just 3.4 parsec away from our Sun. This source hosts an exo-Earth with a projected mass m sin i = 1.35M⊕ and an orbital period of 9.9 days. Ross 128 b receives ∼1.38 times as much flux as Earth from the Sun and its equilibrium ranges in temperature between 269 K for an Earth-like albedo and 213 K for a Venus-like albedo. Recent studies place it close to the inner edge of the conventional habitable zone. An 80-day long light curve from K2 campaign C01 demonstrates that Ross 128 b does not transit. Together with the All Sky Automated Survey (ASAS) photometry and spectroscopic activity indices, the K2 photometry shows that Ross 128 rotates slowly and has weak magnetic activity. In a habitability context, this makes survival of its atmosphere against erosion more likely. Ross 128 b is the second closest known exo-Earth, after Proxima Centauri b (1.3 parsec), and the closest temperate planet known around a quiet star.

Interesting the use of the Kepler K2 data. Not gone unnoticed by the latter :) :

NASA's Kepler/K2 GO Office‏ @KeplerGO
8 hours ago
Did you know?  @NASAKepler observed #Ross128b in 2014!  The discovery paper uses these Kepler data to show that the planet does not transit, and that the host star is magnetically quiet and rotating slowly.  @ESO's #HARPS and @NASA's #K2Mission are a winning combo!

It’s frustrating that both this exoplanet & Proxima b do not transit their star’s from our prospective.
Post by: jebbo on 11/16/2017 07:22 AM
It’s frustrating that both this exoplanet & Proxima b do not transit their star’s from our prospective.

It certainly makes things harder, but both are very near so all is not lost:
* JWST should be able to get low resolution spectroscopy for Proxima b (good enough to detect CO2 and possibly O3).
* Direct imaging is very challenging due to the IWA and contrast requirements but there are various proposals that would manage it (free flying star shades etc)

--- Tony
Post by: Star One on 11/16/2017 07:23 AM
It’s frustrating that both this exoplanet & Proxima b do not transit their star’s from our prospective.

It certainly makes things harder, but both are very near so all is not lost:
* JWST should be able to get low resolution spectroscopy for Proxima b (good enough to detect CO2 and possibly O3).
* Direct imaging is very challenging due to the IWA and contrast requirements but there are various proposals that would manage it (free flying star shades etc)

--- Tony

Is one of them, even though neither transit, better positioned for observation than the other?
Post by: jebbo on 11/16/2017 07:37 AM
Is one of them, even though neither transit, better positioned for observation than the other?

Intuitively I'd say Proxima is easier, purely because it is closer (certainly helps with IWA)

Edit: with a bit of work (a few years), we could get spectra for Proxima b using the VLT.  It needs an upgrade to SPHERE (new coronagraph) and a new fibre feed from the Naysmith A focus to ESPRESSO but it sounds feasible (and fits ESO's strategy of testing instrument for new telescopes on the previous generation).
https://arxiv.org/abs/1609.03082 (https://arxiv.org/abs/1609.03082)

--- Tony
Post by: Star One on 11/16/2017 03:21 PM
Is one of them, even though neither transit, better positioned for observation than the other?

Intuitively I'd say Proxima is easier, purely because it is closer (certainly helps with IWA)

Edit: with a bit of work (a few years), we could get spectra for Proxima b using the VLT.  It needs an upgrade to SPHERE (new coronagraph) and a new fibre feed from the Naysmith A focus to ESPRESSO but it sounds feasible (and fits ESO's strategy of testing instrument for new telescopes on the previous generation).
https://arxiv.org/abs/1609.03082 (https://arxiv.org/abs/1609.03082)

--- Tony

Is Ross 128b just a bit to far then for these instruments?
Post by: jebbo on 11/16/2017 03:44 PM
Is Ross 128b just a bit to far then for these instruments?

Yes ... 2.5 times the distance, so smaller inner working angle (sin(IWA) is inversely proportional to distance). Proxima b is already right at the 2lambda/D limit for 750nm.

--- Tony
Post by: Star One on 11/16/2017 03:53 PM
Is Ross 128b just a bit to far then for these instruments?

Yes ... 2.5 times the distance, so smaller inner working angle (sin(IWA) is inversely proportional to distance). Proxima b is already right at the 2lambda/D limit for 750nm.

--- Tony

So even in the next decade Ross 128b will escape our grasp so to speak.
Post by: jebbo on 11/16/2017 03:55 PM
No, it's probably in range for the 30m class of telescopes.

--- Tony
Post by: Star One on 11/16/2017 04:46 PM
No, it's probably in range for the 30m class of telescopes.

--- Tony

That’s good news then.
Post by: Star One on 11/20/2017 04:23 PM
A Case for an Atmosphere on Super-Earth 55 Cancri e

Quote
One of the primary questions when characterizing Earth-sized and super-Earth-sized exoplanets is whether they have a substantial atmosphere like Earth and Venus or a bare-rock surface like Mercury. Phase curves of the planets in thermal emission provide clues to this question, because a substantial atmosphere would transport heat more efficiently than a bare-rock surface. Analyzing phase-curve photometric data around secondary eclipses has previously been used to study energy transport in the atmospheres of hot Jupiters. Here we use phase curve, Spitzer time-series photometry to study the thermal emission properties of the super-Earth exoplanet 55 Cancri e. We utilize a semianalytical framework to fit a physical model to the infrared photometric data at 4.5 μm. The model uses parameters of planetary properties including Bond albedo, heat redistribution efficiency (i.e., ratio between radiative timescale and advective timescale of the atmosphere), and the atmospheric greenhouse factor. The phase curve of 55 Cancri e is dominated by thermal emission with an eastward-shifted hotspot. We determine the heat redistribution efficiency to be ${1.47}_{-0.25}^{+0.30}$, which implies that the advective timescale is on the same order as the radiative timescale. This requirement cannot be met by the bare-rock planet scenario because heat transport by currents of molten lava would be too slow. The phase curve thus favors the scenario with a substantial atmosphere. Our constraints on the heat redistribution efficiency translate to an atmospheric pressure of ~1.4 bar. The Spitzer 4.5 μm band is thus a window into the deep atmosphere of the planet 55 Cancri e.

http://iopscience.iop.org/article/10.3847/1538-3881/aa9278
Post by: Star One on 11/20/2017 04:53 PM
Giant telescope’s mobile-phone ‘dead zones’ rile South African residents

Quote
Sensitive radio dishes of the Square Kilometre Array will affect phone reception — and could harm local economies, say farmers.

Post by: Star One on 11/20/2017 07:18 PM
Phil Plait debunks the latest moon hoax nonsense and despairs that even Newsweek reproduced these ridiculous claims.

Quote
And it denigrates science. It demeans one of the most amazing challenges humans have ever undertaken, one of the greatest accomplishments in our history.

Perhaps even worse, it's painful to see a magazine like Newsweek promulgate such nonsense. I'll note in the article the writer didn't seek out any expert advice, despite a dozen people who could be found easily using a Google search. I'm one of them, and it took me literally three minutes to figure out exactly what's what in this photo. So yeah, it's irritating (though I'll very grudgingly give Streetcap1 one small piece of credit: He at least links to the original image; most conspiracy theorists don't, which should ring very loud alarm bells).

If there's a lesson to be learned here, it's that this little episode shows how flawed humans can be, how easily we can be swayed by the flimsiest of claims. That is part of our nature… just as it's part of our nature to seek out truth, to investigate the unknown, and to explore it. And while critical thinking and judicious skepticism are harder to implement, and may not be part of our nature, I'll remind you that we invented science. We recognize that we can be fooled, and we created an entire field of thinking and investigation to minimize that issue.

And the beauty is, it works!

After all, for real and for sure, it sent us to the Moon.

http://www.syfy.com/syfywire/no-thats-not-a-stagehand-in-an-apollo-astronaut-photo
Post by: Star One on 11/28/2017 05:15 PM
Seeing Double with K2: Testing Re-inflation with Two Remarkably Similar Planets around Red Giant Branch Stars

Quote
Despite more than 20 years since the discovery of the first gas giant planet with an anomalously large radius, the mechanism for planet inflation remains unknown. Here, we report the discovery of K2-132b, an inflated gas giant planet found with the NASA K2 Mission, and a revised mass for another inflated planet, K2-97b. These planets orbit on ≈9 day orbits around host stars that recently evolved into red giants. We constrain the irradiation history of these planets using models constrained by asteroseismology and Keck/High Resolution Echelle Spectrometer spectroscopy and radial velocity measurements. We measure planet radii of 1.31 ± 0.11 R J and 1.30 ± 0.07 R J, respectively. These radii are typical for planets receiving the current irradiation, but not the former, zero age main-sequence irradiation of these planets. This suggests that the current sizes of these planets are directly correlated to their current irradiation. Our precise constraints of the masses and radii of the stars and planets in these systems allow us to constrain the planetary heating efficiency of both systems as $0.03{ \% }_{-0.02 \% }^{+0.03 \% }$. These results are consistent with a planet re-inflation scenario, but suggest that the efficiency of planet re-inflation may be lower than previously theorized. Finally, we discuss the agreement within 10% of the stellar masses and radii, and the planet masses, radii, and orbital periods of both systems, and speculate that this may be due to selection bias in searching for planets around evolved stars.

http://iopscience.iop.org/article/10.3847/1538-3881/aa932d
Post by: Star One on 11/30/2017 08:56 PM
Subsurface Exolife

Quote
We study the prospects for life on planets with subsurface oceans, and find that a wide range of planets can exist in diverse habitats with relatively thin ice envelopes. We quantify the energy sources available to these worlds, the rate of production of prebiotic compounds, and assess their potential for hosting biospheres. Life on these planets is likely to face challenges, which could be overcome through a combination of different mechanisms. We quantify the number of such worlds, and find that they may outnumber rocky planets in the habitable zone of stars by a few orders of magnitude.

https://arxiv.org/abs/1711.09908
Post by: Star One on 12/01/2017 07:53 PM
Giant black hole pair photobombs Andromeda galaxy

Quote
It seems like even black holes can’t resist the temptation to insert themselves unannounced into photographs. A cosmic photobomb found as a background object in images of the nearby Andromeda galaxy has revealed what could be the most tightly coupled pair of supermassive black holes ever seen.

https://astronomynow.com/2017/12/01/giant-black-hole-pair-photobombs-andromeda-galaxy/

A Microlensing Event Seen from Three Positions in Space

Quote
In a new paper, Yee and a large team of her colleagues report the first microlensing event seen from three well-separated points: Spitzer, the Earth, and the Kepler “K2” mission, which has an orbit similar to that of Spitzer but which currently trails the Earth about one-sixth of the way around in its orbital path. The lensing object, known as MOA-2016-BLG-290, was determined from these measurements to be an extremely low mass star of about .07 solar-masses (seventy-seven Jupiter-masses), and situated about twenty-two thousand light-years away in our galaxy. The result, besides detecting an object intermediate in mass between a star and a planet, demonstrates the power of microlensing parallax measurements predicted decades ago.

https://www.cfa.harvard.edu/news/su201745

The habitability of the Milky Way during the active phase of its central supermassive black hole

Quote
During the peak of their accretion phase, supermassive black holes in galactic cores are known to emit very high levels of ionizing radiation, becoming visible over intergalactic distances as quasars or active galactic nuclei (AGN). Here, we quantify the extent to which the activity of the supermassive black hole at the center of the Milky Way, known as Sagittarius A* (Sgr A*), may have affected the habitability of Earth-like planets in our Galaxy. We focus on the amount of atmospheric loss and on the possible biological damage suffered by planets exposed to X-ray and extreme ultraviolet (XUV) radiation produced during the peak of the active phase of Sgr A*. We find that terrestrial planets could lose a total atmospheric mass comparable to that of present day Earth even at large distances (~1 kiloparsec) from the galactic center. Furthermore, we find that the direct biological damage caused by Sgr A* to surface life on planets not properly screened by an atmosphere was probably significant during the AGN phase, possibly hindering the development of complex life within a few kiloparsecs from the galactic center.

https://arxiv.org/abs/1711.11318
Post by: Star One on 12/05/2017 08:22 PM
Trickle-down is the Solution (to the Planetary Core Formation Problem)

Quote
Scientists have long pondered how rocky bodies in the solar system—including our own Earth—got their metal cores. According to research conducted by The University of Texas at Austin, evidence points to the downwards percolation of molten metal toward the center of the planet through tiny channels between grains of rock.

The finding calls into question the interpretation of prior experiments and simulations that sought to understand how metals behave under intense heat and pressure when planets are forming. Past results suggested that large portions of molten metals stayed trapped in isolated pores between the grains. In contrast, the new research suggests that once those isolated pores grow large enough to connect,  the molten metal starts to flow, and most of it is able to percolate along grain boundaries. This process would let metal trickle down through the mantle, accumulate in the center, and form a metal core, like the iron core at the heart of our home planet.

https://www.jsg.utexas.edu/news/2017/12/trickle-down-is-the-solution-to-the-planetary-core-formation-problem/
Post by: Star One on 12/06/2017 05:54 PM
Researchers find exciting potential for little-known exoplanet – and discover another planet in the process

Quote
New research using data collected by the European Southern Observatory (ESO) has revealed that a little-known exoplanet called K2-18b could well be a scaled-up version of Earth.

Just as exciting, the same researchers also discovered for the first time that the planet has a neighbor.

“Being able to measure the mass and density of K2-18b was tremendous, but to discover a new exoplanet was lucky and equally exciting,” says lead author Ryan Cloutier, a PhD student in U of T Scarborough’s Centre for Planet Science, U of T’s Department of Astronomy and Astrophysics, and Université de Montréal Institute for research on exoplanets (iREx).

Both planets orbit K2-18, a red-dwarf star located about 111 light years away in the constellation Leo. When the planet K2-18b was first discovered in 2015, it was found to be orbiting within the star’s habitable zone, making it an ideal candidate to have liquid surface water, a key element in harbouring conditions for life as we know it.

https://utsc.utoronto.ca/news-events/breaking-research/researchers-find-exciting-potential-little-known-exoplanet-and-discover-another
Post by: Star One on 12/06/2017 08:03 PM
Found: The most distant supermassive black hole ever observed

Quote
A team of astronomers led by Carnegie’s Eduardo Bañados used Carnegie’s Magellan telescopes to discover the most-distant supermassive black hole ever observed. It resides in a luminous quasar and its light reaches us from when the Universe was only 5 percent of its current age — just 690 million years after the Big Bang.

Quasars are tremendously bright objects comprised of enormous black holes accreting matter at the centers of massive galaxies. This newly discovered black hole has a mass that is 800 million times the mass of our Sun.

“Gathering all this mass in fewer than 690 million years is an enormous challenge for theories of supermassive black hole growth,” Bañados explained.

https://astronomynow.com/2017/12/06/found-the-most-distant-supermassive-black-hole-ever-observed/
Post by: jebbo on 12/07/2017 05:20 PM
The E-ELT mirror is now fully funded.

--- Tony
Post by: Star One on 12/12/2017 07:53 PM
Meteorite’s origins point to possible undiscovered asteroid

Quote
A new analysis of a meteorite called Bunburra Rockhole has revealed that the rock originated from a previously unknown parent asteroid, allowing scientists to understand the geology of the parent body.

The parent body was differentiated, meaning that it was large enough to separate into a core, mantle and crust, and was roughly spherical in shape, though not as large as a planet. Identifying a new differentiated asteroid is vital for understanding the formation of asteroids and planets in the Solar System. Most of the large asteroids in the Asteroid Belt are already known, so this means that either the meteorite originated on an asteroid that has been eroded, or there is another large asteroid out there.

Bunburra Rockhole was the first meteorite to be recovered using the Desert Fireball Network, a network of cameras across Australia that observe where meteoroids enter the atmosphere. These cameras make it possible to determine the orbit of a meteorite prior to its descent to Earth. Models of the orbit of Bunburra Rockhole placed its origin within the innermost, main asteroid belt, interior to Vesta, the second-largest body in the Asteroid Belt between Mars and Jupiter.

https://astronomynow.com/2017/12/11/meteorites-origins-point-to-possible-undiscovered-asteroid/
Post by: redliox on 12/12/2017 10:03 PM
Posted an astronomy relevant question in regards to finding out nearest exoplanets:
https://space.stackexchange.com/questions/24010/could-a-21-meter-space-telescope-detect-the-nearest-exoplanets (https://space.stackexchange.com/questions/24010/could-a-21-meter-space-telescope-detect-the-nearest-exoplanets)
Post by: Star One on 12/13/2017 08:01 PM
Amongst the 86 official star names allocated by the IAU Barnard’s Star officially gains that name 100 years after its discovery by Edward Emerson Barnard.

https://www.iau.org/news/pressreleases/detail/iau1707/
Post by: Dao Angkan on 12/13/2017 08:40 PM
Extragalactic exoplanets could be detected by the Large Synoptic Survey Telescope.

Can gravitational microlensing detect extragalactic exoplanets? Self-lensing models of the Small Magellanic Cloud (https://arxiv.org/abs/1712.03986)

Also, ESPRESSO sees first light (https://www.eso.org/public/news/eso1739/). It should achieve precision of at least an order of magnitude over HARPS.
Post by: redliox on 12/13/2017 10:22 PM
Extragalactic exoplanets could be detected by the Large Synoptic Survey Telescope.

Can gravitational microlensing detect extragalactic exoplanets? Self-lensing models of the Small Magellanic Cloud (https://arxiv.org/abs/1712.03986)

Also, ESPRESSO sees first light (https://www.eso.org/public/news/eso1739/). It should achieve precision of at least an order of magnitude over HARPS.

Every time I hear about the discovery of some planet 1,000 light years away...I can't help thinking "And we still don't know how many planets are around Alpha Centauri yet."  At least Proxima b makes a start...

I will say finding exoplanets in an entirely different galaxy is impressive.
Post by: Dao Angkan on 12/14/2017 04:16 PM
Detection by radial velocity is probably the best bet for discovering more planets around the Alpha Centauri system and other relatively nearby stars. ESPRESSO and EXPRES (https://arxiv.org/abs/1606.04413) should help with this in the near term.

Microlensing is great for distant stars, currently several exoplanets have been discovered at over 20,000 LY distance. The Small Magellanic Cloud is ~200,000 LY away.
Post by: the_other_Doug on 12/14/2017 10:45 PM
Has anyone come up with what our own sun's radial velocity perturbations would look like from a variety of distances and with a variety of viewing "resolutions"?

In other words, how easy would it be from 30 light-years away, for example, to examine Sol and state that it has four inner rocky planets and four outer gas / ice giants?  How easy from 300?  From 3,000?  Et cetera...
Post by: Alpha_Centauri on 12/15/2017 12:05 PM
Typical angular resolution isn't the problem with RV as you only need an unresolved blob of light. The main limiting factors are things like getting enough photons to flesh out the spectrum (either use a big enough light bucket / telescope / array, or viewing brighter stars), a high enough spectrograph resolution to separate out absorption lines, and the intrinsic "noise" largely due to stellar activity.

Our Sun has a decent luminosity so would be viewable for spectrographs like ours for quite some distance. It is also pretty quiet in comparison to many stars, so I think it would be on any alien astronomers target list. I don't know about exact figures. Of course on the other hand our solar system has one rather big downside; compared with many other systems most of our planets are quite some distance from our star and so have long orbital periods, so monitoring to get large enough orbital arcs to improve S/N would take some time.

I believe radial velocity observations of sunlight were conducted in the past, especially back when people were first thinking about finding planets using RV in the 90s. There will be papers on it somewhere. Obviously our instruments have inmproved significantly since then.
Post by: jebbo on 12/18/2017 11:24 AM
Two interesting exoplanet papers today

First, more detail of the "Fulton gap" in planet radii:

Exoplanet Radius Gap Dependence on Host Star Type
Quote
Exoplanets smaller than Neptune are numerous, but the nature of the planet populations in the 1-4 Earth radii range remains a mystery. The complete Kepler sample of Q1-Q17 exoplanet candidates shows a radius gap at ~ 2 Earth radii, as reported by us in January 2017 in LPSC conference abstract #1576 (Zeng et al. 2017). A careful analysis of Kepler host stars spectroscopy by the CKS survey allowed Fulton et al. (2017) in March 2017 to unambiguously show this radius gap. The cause of this gap is still under discussion (Ginzburg et al. 2017; Lehmer & Catling 2017; Owen & Wu 2017). Here we add to our original analysis the dependence of the radius gap on host star type.
https://arxiv.org/abs/1712.05458 (https://arxiv.org/abs/1712.05458)

Second, a study of tidal heating in the TRAPPIST-1 system:

Interior Structures and Tidal Heating in the TRAPPIST-1 Planets
Quote
With seven planets, the TRAPPIST-1 system has the largest number of exoplanets discovered in a single system so far. The system is of astrobiological interest, because three of its planets orbit in the habitable zone of the ultracool M dwarf. Assuming the planets are composed of non-compressible iron, rock, and H2O, we determine possible interior structures for each planet. To determine how much tidal heat may be dissipated within each planet, we construct a tidal heat generation model using a single uniform viscosity and rigidity for each planet based on the planet's composition. With the exception of TRAPPIST-1c, all seven of the planets have densities low enough to indicate the presence of significant H2O in some form. Planets b and c experience enough heating from planetary tides to maintain magma oceans in their rock mantles; planet c may have eruptions of silicate magma on its surface, which may be detectable with next-generation instrumentation. Tidal heat fluxes on planets d, e, and f are lower, but are still twenty times higher than Earth's mean heat flow. Planets d and e are the most likely to be habitable. Planet d avoids the runaway greenhouse state if its albedo is ≳ 0.3. Determining the planet's masses within ∼0.1 to 0.5 Earth masses would confirm or rule out the presence of H2O and/or iron in each planet, and permit detailed models of heat production and transport in each planet. Understanding the geodynamics of ice-rich planets f, g, and h requires more sophisticated modeling that can self-consistently balance heat production and transport in both rock and ice layers.
https://arxiv.org/abs/1712.05641 (https://arxiv.org/abs/1712.05641)

I'm still dubious of the density measurements in this system ... they'll be much more certain once we get RV data from instruments like SPIROU

--- Tony

Post by: Star One on 12/18/2017 07:55 PM
Two interesting exoplanet papers today

First, more detail of the "Fulton gap" in planet radii:

Exoplanet Radius Gap Dependence on Host Star Type
Quote
Exoplanets smaller than Neptune are numerous, but the nature of the planet populations in the 1-4 Earth radii range remains a mystery. The complete Kepler sample of Q1-Q17 exoplanet candidates shows a radius gap at ~ 2 Earth radii, as reported by us in January 2017 in LPSC conference abstract #1576 (Zeng et al. 2017). A careful analysis of Kepler host stars spectroscopy by the CKS survey allowed Fulton et al. (2017) in March 2017 to unambiguously show this radius gap. The cause of this gap is still under discussion (Ginzburg et al. 2017; Lehmer & Catling 2017; Owen & Wu 2017). Here we add to our original analysis the dependence of the radius gap on host star type.
https://arxiv.org/abs/1712.05458 (https://arxiv.org/abs/1712.05458)

Second, a study of tidal heating in the TRAPPIST-1 system:

Interior Structures and Tidal Heating in the TRAPPIST-1 Planets
Quote
With seven planets, the TRAPPIST-1 system has the largest number of exoplanets discovered in a single system so far. The system is of astrobiological interest, because three of its planets orbit in the habitable zone of the ultracool M dwarf. Assuming the planets are composed of non-compressible iron, rock, and H2O, we determine possible interior structures for each planet. To determine how much tidal heat may be dissipated within each planet, we construct a tidal heat generation model using a single uniform viscosity and rigidity for each planet based on the planet's composition. With the exception of TRAPPIST-1c, all seven of the planets have densities low enough to indicate the presence of significant H2O in some form. Planets b and c experience enough heating from planetary tides to maintain magma oceans in their rock mantles; planet c may have eruptions of silicate magma on its surface, which may be detectable with next-generation instrumentation. Tidal heat fluxes on planets d, e, and f are lower, but are still twenty times higher than Earth's mean heat flow. Planets d and e are the most likely to be habitable. Planet d avoids the runaway greenhouse state if its albedo is ≳ 0.3. Determining the planet's masses within ∼0.1 to 0.5 Earth masses would confirm or rule out the presence of H2O and/or iron in each planet, and permit detailed models of heat production and transport in each planet. Understanding the geodynamics of ice-rich planets f, g, and h requires more sophisticated modeling that can self-consistently balance heat production and transport in both rock and ice layers.
https://arxiv.org/abs/1712.05641 (https://arxiv.org/abs/1712.05641)

I'm still dubious of the density measurements in this system ... they'll be much more certain once we get RV data from instruments like SPIROU

--- Tony

First paper listed above comes under criticism for being an example of ‘flag planting’, half finished and not the appropriate forum for discussing the topic.

Post by: jebbo on 12/19/2017 06:27 AM
First paper listed above comes under criticism for being an example of ‘flag planting’, half finished and not the appropriate forum for discussing the topic.

Yes, I saw that ... it was a discussion over the purpose of the (extremely new) "Research Notes" rather than a critique of the paper (don't think anyone questioned the data).  To me, leaving aside the flag-planting issue, it seems in the spirit of RN: small contributions that either need follow-up or are not worth a paper in their own right.

The wider discussion surrounding this bit was more interesting: when should effects be named after people.

--- Tony
Post by: Star One on 12/19/2017 06:37 AM
First paper listed above comes under criticism for being an example of ‘flag planting’, half finished and not the appropriate forum for discussing the topic.

Yes, I saw that ... it was a discussion over the purpose of the (extremely new) "Research Notes" rather than a critique of the paper (don't think anyone questioned the data).  To me, leaving aside the flag-planting issue, it seems in the spirit of RN: small contributions that either need follow-up or are not worth a paper in their own right.

The wider discussion surrounding this bit was more interesting: when should effects be named after people.

--- Tony

Yes I noticed the naming issue. I know Twitter isn’t a very good basis for judging these things but the consensus seemed to be against the naming in this case
Post by: jebbo on 12/19/2017 07:00 AM
Yes I noticed the naming issue. I know Twitter isn’t a very good basis for judging these things but the consensus seemed to be against the naming in this case

Yes ... hardly surprising as the whole "Fulton gap" name was really just a bit of a running gag on Twitter.  Photo-evaporation valley is short and descriptive enough.

--- Tony
Post by: as58 on 12/19/2017 07:59 AM
I must admit that I don't see the point of RNAAS when everything is put on arxiv anyway. To me it seems like a flag-planting operation by AAS...
Post by: jebbo on 12/20/2017 08:41 AM
Predictions of planet detections with near infrared radial velocities in the up-coming SPIRou Legacy Survey-Planet Search
Quote
The SPIRou near infrared spectro-polarimeter is destined to begin science operations at the Canada-France-Hawaii Telescope in mid-2018. One of the instrument's primary science goals is to discover the closest exoplanets to the Solar System by conducting a 3-5 year long radial velocity survey of nearby M dwarfs at an expected precision of ∼1 m s−1; the SPIRou Legacy Survey-Planet Search (SLS-PS). In this study we conduct a detailed Monte-Carlo simulation of the SLS-PS using our current understanding of the occurrence rate of M dwarf planetary systems and physical models of stellar activity. From simultaneous modelling of planetary signals and activity, we predict the population of planets detected in the SLS-PS. With our fiducial survey strategy and expected instrument performance over a nominal survey length of ∼3 years, we expect SPIRou to detect 85.3+29.3−12.4 planets including 20.0+16.8−7.2 habitable zone planets and 8.1+7.6−3.2 Earth-like planets from a sample of 100 M1-M8.5 dwarfs out to 11 pc. By studying mid-to-late M dwarfs previously inaccessible to existing optical velocimeters, SPIRou will put meaningful constraints on the occurrence rate of planets around those stars including the value of η⊕ at an expected level of precision of ≲45%. We also predict a subset of 46.7+16.0−6.0 planets may be accessible with dedicated high-contrast imagers on the next generation of ELTs including 4.9+4.7−2.0 potentially imagable Earth-like planets. Lastly, we compare the results of our fiducial survey strategy to other foreseeable survey versions to quantify which strategy is optimized to reach the SLS-PS science goals. The results of our simulations are made available to the community on github.
https://arxiv.org/abs/1712.06673 (https://arxiv.org/abs/1712.06673)

I'm looking forward to the results from this one!  First, it should give us much better masses for Proxima b and the TRAPPIST-1 planets; second, it should yield a few direct imaging targets for the forthcoming 30m class telescopes.

--- Tony
Post by: Star One on 12/20/2017 08:07 PM
Giant Bubbles on Red Giant Star’s Surface

Quote
Astronomers using ESO’s Very Large Telescope have for the first time directly observed granulation patterns on the surface of a star outside the Solar System — the ageing red giant π1 Gruis. This remarkable new image from the PIONIER instrument reveals the convective cells that make up the surface of this huge star, which has 350 times the diameter of the Sun. Each cell covers more than a quarter of the star’s diameter and measures about 120 million kilometres across. These new results are being published this week in the journal Nature.

http://www.eso.org/public/news/eso1741/

Post by: Star One on 12/22/2017 07:24 PM
The cool and distant formation of Mars

Quote
With approximately one ninth of Earth's mass, Mars is widely considered to be a stranded planetary embryo that never became a fully-grown planet. A currently popular planet formation theory predicts that Mars formed near Earth and Venus and was subsequently scattered outwards to its present location. In such a scenario, the compositions of the three planets are expected to be similar to each other. However, bulk elemental and isotopic data for martian meteorites demonstrate that key aspects of Mars' composition are markedly different from that of Earth. This suggests that Mars formed outside of the terrestrial feeding zone during primary accretion. It is therefore probable that Mars always remained significantly farther from the Sun than Earth; its growth was stunted early and its mass remained relatively low. Here we identify a potential dynamical pathway that forms Mars in the asteroid belt and keeps it outside of Earth's accretion zone while at the same time accounting for strict age and compositional constraints, as well as mass differences. Our uncommon pathway (approximately 2% probability) is based on the Grand Tack scenario of terrestrial planet formation, in which the radial migration by Jupiter gravitationally sculpts the planetesimal disc at Mars' current location. We conclude that Mars' formation requires a specific dynamical pathway, while this is less valid for Earth and Venus. We further predict that Mars' volatile budget is most likely different from Earth's and that Venus formed close enough to our planet that it is expected to have a nearly identical composition from common building blocks.

http://www.sciencedirect.com/science/article/pii/S0012821X1730184X?via%3Dihub#!

https://arxiv.org/pdf/1704.00184.pdf
Post by: Star One on 12/28/2017 05:05 PM
The origins of our solar system?

Triggered Star Formation inside the Shell of a Wolf–Rayet Bubble as the Origin of the Solar System

Quote
A critical constraint on solar system formation is the high ${}^{26}\mathrm{Al}$/27Al abundance ratio of $5\times {10}^{-5}$ at the time of formation, which was about 17 times higher than the average Galactic ratio, while the 60Fe/56Fe value was about $2\times {10}^{-8}$, lower than the Galactic value. This challenges the assumption that a nearby supernova (SN) was responsible for the injection of these short-lived radionuclides into the early solar system. We show that this conundrum can be resolved if the solar system was formed by a triggered star formation at the edge of a Wolf–Rayet (W–R) bubble. 26Al is produced during the evolution of the massive star, released in the wind during the W–R phase, and condenses into dust grains that are seen around W–R stars. The dust grains survive passage through the reverse shock and the low-density shocked wind, reach the dense shell swept-up by the bubble, detach from the decelerated wind, and are injected into the shell. Some portions of this shell subsequently collapse to form the dense cores that give rise to solar-type systems. The subsequent aspherical SN does not inject appreciable amounts of ${}^{60}\mathrm{Fe}$ into the proto–solar system, thus accounting for the observed low abundance of ${}^{60}\mathrm{Fe}$. We discuss the details of various processes within the model and conclude that it is a viable model that can explain the initial abundances of ${}^{26}\mathrm{Al}$ and ${}^{60}\mathrm{Fe}$. We estimate that 1%–16% of all Sun-like stars could have formed in such a setting of triggered star formation in the shell of a W–R bubble.

http://iopscience.iop.org/article/10.3847/1538-4357/aa992e/meta
Post by: ExoExplorer on 01/03/2018 05:29 PM
Predictions of planet detections with near infrared radial velocities in the up-coming SPIRou Legacy Survey-Planet Search
Quote
The SPIRou near infrared spectro-polarimeter is destined to begin science operations at the Canada-France-Hawaii Telescope in mid-2018. One of the instrument's primary science goals is to discover the closest exoplanets to the Solar System by conducting a 3-5 year long radial velocity survey of nearby M dwarfs at an expected precision of ∼1 m s−1; the SPIRou Legacy Survey-Planet Search (SLS-PS). In this study we conduct a detailed Monte-Carlo simulation of the SLS-PS using our current understanding of the occurrence rate of M dwarf planetary systems and physical models of stellar activity. From simultaneous modelling of planetary signals and activity, we predict the population of planets detected in the SLS-PS. With our fiducial survey strategy and expected instrument performance over a nominal survey length of ∼3 years, we expect SPIRou to detect 85.3+29.3−12.4 planets including 20.0+16.8−7.2 habitable zone planets and 8.1+7.6−3.2 Earth-like planets from a sample of 100 M1-M8.5 dwarfs out to 11 pc. By studying mid-to-late M dwarfs previously inaccessible to existing optical velocimeters, SPIRou will put meaningful constraints on the occurrence rate of planets around those stars including the value of η⊕ at an expected level of precision of ≲45%. We also predict a subset of 46.7+16.0−6.0 planets may be accessible with dedicated high-contrast imagers on the next generation of ELTs including 4.9+4.7−2.0 potentially imagable Earth-like planets. Lastly, we compare the results of our fiducial survey strategy to other foreseeable survey versions to quantify which strategy is optimized to reach the SLS-PS science goals. The results of our simulations are made available to the community on github.
https://arxiv.org/abs/1712.06673 (https://arxiv.org/abs/1712.06673)

I'm looking forward to the results from this one!  First, it should give us much better masses for Proxima b and the TRAPPIST-1 planets; second, it should yield a few direct imaging targets for the forthcoming 30m class telescopes.

--- Tony
SLS-PS is unlikely to detect the radial velocity of TRAPPIST-1 (mv = 19). It's just simply too faint for Doppler spectroscopy.
Post by: jebbo on 01/03/2018 05:39 PM
SLS-PS is unlikely to detect the radial velocity of TRAPPIST-1 (mv = 19). It's just simply too faint for Doppler spectroscopy.

Yes, it is very dim in the V band, but it is much brighter in IR. Also, I didn't post that blind, I asked them ages ago:

Quote
with IR mags of J=11, H=10.7 and K=10.3, Trappist-1 is in reach of SPIRou_astro. no doubt SPIRou_astro will look at it once on CFHT

Quote
W/ expected RV amplitudes of 0.9 to 3.5m/s, Trappist-1 planets b to h may be better characterized in mass & density w/ SPIRou_astro

--- Tony

Post by: ExoExplorer on 01/03/2018 05:53 PM
Typical angular resolution isn't the problem with RV as you only need an unresolved blob of light. The main limiting factors are things like getting enough photons to flesh out the spectrum (either use a big enough light bucket / telescope / array, or viewing brighter stars), a high enough spectrograph resolution to separate out absorption lines, and the intrinsic "noise" largely due to stellar activity.

Our Sun has a decent luminosity so would be viewable for spectrographs like ours for quite some distance. It is also pretty quiet in comparison to many stars, so I think it would be on any alien astronomers target list. I don't know about exact figures. Of course on the other hand our solar system has one rather big downside; compared with many other systems most of our planets are quite some distance from our star and so have long orbital periods, so monitoring to get large enough orbital arcs to improve S/N would take some time.

I believe radial velocity observations of sunlight were conducted in the past, especially back when people were first thinking about finding planets using RV in the 90s. There will be papers on it somewhere. Obviously our instruments have inmproved significantly since then.
The orbital inclination of the alien Earth would also limit the measurable amplitude of wobble. For example, if the inclination is close to 0°, the planet would be undetectable by RV regardless of how precise.
Post by: ExoExplorer on 01/03/2018 06:23 PM
SLS-PS is unlikely to detect the radial velocity of TRAPPIST-1 (mv = 19). It's just simply too faint for Doppler spectroscopy.

Yes, it is very dim in the V band, but it is much brighter in IR. Also, I didn't post that blind, I asked them ages ago:

Quote
with IR mags of J=11, H=10.7 and K=10.3, Trappist-1 is in reach of SPIRou_astro. no doubt SPIRou_astro will look at it once on CFHT

Quote
W/ expected RV amplitudes of 0.9 to 3.5m/s, Trappist-1 planets b to h may be better characterized in mass & density w/ SPIRou_astro

--- Tony
How surprising. I thought it would be impossible in the short-term, but the outer three planets are hardly achievable since low-density materials like ice probably make up a significant part of their masses. Combination of RV and TTV would constrain the whole system with better precision I believe.
Post by: Star One on 01/09/2018 05:00 PM
Extra-Terrestrial Hypatia Stone Rattles Solar System Status Quo

https://scienmag.com/extra-terrestrial-hypatia-stone-rattles-solar-system-status-quo/
Post by: Bynaus on 01/09/2018 06:58 PM
Extra-Terrestrial Hypatia Stone Rattles Solar System Status Quo

https://scienmag.com/extra-terrestrial-hypatia-stone-rattles-solar-system-status-quo/

A couple of years ago, I was co-author on a paper studying the Hypatia stone (https://arxiv.org/abs/1510.06594). The stone is clearly extraterrestrial, yes, but I think this whole story is getting blown way out of proportion in the new paper.

First, its not like carbon-dominated materials are unheard off in meteorites - we identified several possibilities in our paper, the strongest, in my opinion, being that the stone is shock-compressed (thus diamond-bearing) graphite nodule from an iron meteorite (there is actually additional support for this from the Fe, Ni, S and P phases the authors of the new paper report - all these elements are abundant in iron meteorites).

Second, the claim of a pre-solar origin would require the identification of the characteristically large isotopic anomalies, which the authors of the new paper do not report.
Post by: Star One on 01/09/2018 08:13 PM
White dwarf’s inner makeup is mapped for the first time

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Astronomers have probed the inner life of a dead star. Tiny changes in a white dwarf’s brightness reveal that the stellar corpse has more oxygen in its core than expected, researchers report online January 8 in Nature. The finding could challenge theories of how stars live and die, and may have implications for measuring the expansion of the universe.

Quote
More recent observations suggest that these so-called standard candles may not be so standard after all. If the white dwarfs that help create supernovas have varying oxygen contents, that may help explain some of the differences, Fontaine says.

Accounting for that difference may someday help reveal details of what dark energy is made of, says astrophysicist Alexei Filippenko of the University of California, Berkeley. But those implications are a long way off. “Just how much bearing it will have on cosmology remains to be seen,” he says.

https://www.sciencenews.org/article/white-dwarfs-inner-makeup-mapped-first-time
Post by: fthomassy on 01/09/2018 10:38 PM
Cross posting as it might relate to astronomy tracking too ...
Incredible footage of stage sep and the boostback burn.

Thanks!  That was my video. I'm hoping at some point other launch regulars who do tracking shots start to adopt my setup and software for their shots as well.  The software is very experimental, but it's freely available.  Computer, joystick, and telescope not included, of course.
Post by: Star One on 01/10/2018 07:17 PM
Across the universe, fast radio bursts ‘shout and twist’

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An international group of astronomers has found that the Cornell-discovered fast radio burst FRB 121102 – a brief, gigantic pulse of radio waves from 3 billion light years away – passes through a veil of magnetized plasma. This causes the cosmic blasts to “shout and twist,” which will help the scientists determine the source.

The research is featured on the cover of Nature, Jan. 11.

The “shouting” represents the bursts, and the “twisting” describes a physical phenomenon called Faraday rotation, which occurs as radio waves pass through a magnetized plasma, explained James Cordes, the George Feldstein Professor of Astronomy. Measurement of the twisting provides further scientific detail on the origin of FRB 121102. The data were culled from the Arecibo Observatory in Puerto Rico and confirmed by Green Bank Observatory in West Virginia.

Post by: Star One on 01/11/2018 08:52 PM
The K2-138 System: A Near-resonant Chain of Five Sub-Neptune Planets Discovered by Citizen Scientists

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K2-138 is a moderately bright (V = 12.2, K = 10.3) main-sequence K star observed in Campaign 12 of the NASA K2 mission. It hosts five small (1.6–3.3 ${R}_{\oplus }$) transiting planets in a compact architecture. The periods of the five planets are 2.35, 3.56, 5.40, 8.26, and 12.76 days, forming an unbroken chain of near 3:2 resonances. Although we do not detect the predicted 2–5 minute transit timing variations (TTVs) with the K2 timing precision, they may be observable by higher-cadence observations with, for example, Spitzer or CHEOPS. The planets are amenable to mass measurement by precision radial velocity measurements, and therefore K2-138 could represent a new benchmark system for comparing radial velocity and TTV masses. K2-138 is the first exoplanet discovery by citizen scientists participating in the Exoplanet Explorers project on the Zooniverse platform.

http://iopscience.iop.org/article/10.3847/1538-3881/aa9be0
Post by: jebbo on 01/12/2018 09:31 AM
The K2-138 System: A Near-resonant Chain of Five Sub-Neptune Planets Discovered by Citizen Scientists

Yes, this is a very interesting one: the two transits at ~42 days that suggest a sixth planet are consistent with the 3/2 resonance chain ... if you skip two slots at ~18.6 days and 27.9 days

--- Tony
Post by: Star One on 01/12/2018 09:35 AM
The K2-138 System: A Near-resonant Chain of Five Sub-Neptune Planets Discovered by Citizen Scientists

Yes, this is a very interesting one: the two transits at ~42 days that suggest a sixth planet are consistent with the 3/2 resonance chain ... if you skip two slots at ~18.6 days and 27.9 days

--- Tony

Go and have a quick look at Professor Chris Lintott’s twitter account as he talks about that very thing on there.
Post by: Star One on 01/12/2018 12:53 PM
Meet the amateur astronomers who track secretive spy satellites for fun

https://www.popsci.com/zuma-spy-satellite-amateur-astronomer
Post by: Star One on 01/12/2018 07:36 PM
We may be able to see mountains and valleys on distant worlds

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Moiya McTier at Columbia University in New York presented her research into the embryonic field of exotopography on 11 January at a meeting of the American Astronomical Society. She says that by analysing the dip in a star’s light as a planet passes in front of it, we might be able to discern actual details about the planet’s landscape.

None of the rocky planets in our solar system are perfectly round: there are mountains, canyons, craters and other features that carve elevations high and low across a surface. So why shouldn’t there be similar features on planets orbiting other stars?

McTier took US Geological Survey maps of our four terrestrial planets and the Moon to determine what their light curve around

https://www.newscientist.com/article/2158466-we-may-be-able-to-see-mountains-and-valleys-on-distant-worlds
Post by: CuddlyRocket on 01/13/2018 05:53 PM
The K2-138 System: A Near-resonant Chain of Five Sub-Neptune Planets Discovered by Citizen Scientists

Yes, this is a very interesting one: the two transits at ~42 days that suggest a sixth planet are consistent with the 3/2 resonance chain ... if you skip two slots at ~18.6 days and 27.9 days

55.8 days, and any multiple thereof, is a whole number multiple of both 18.6 and 27.9. So, perhaps there's something larger with such an orbital period, but not a multiple of ~42 days, that disrupted the formation of any planets at those two slots? If the orbital period is long enough it might not have transited during the observation run.
Post by: Star One on 01/16/2018 07:33 PM
Ingredients for life revealed in meteorites that fell to Earth

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Two wayward space rocks, which separately crashed to Earth in 1998 after circulating in our solar system’s asteroid belt for billions of years, share something else in common: the ingredients for life. They are the first meteorites found to contain both liquid water and a mix of complex organic compounds such as hydrocarbons and amino acids.

A detailed study of the chemical makeup within tiny blue and purple salt crystals sampled from these meteorites, which included results from X-ray experiments at the Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab), also found evidence for the pair’s past intermingling and likely parents. These include Ceres, a brown dwarf planet that is the largest object in the asteroid belt, and the asteroid Hebe, a major source of meteorites that fall on Earth.

https://astronomynow.com/2018/01/16/ingredients-for-life-revealed-in-meteorites-that-fell-to-earth/
Post by: jgoldader on 01/16/2018 08:36 PM
Ingredients for life revealed in meteorites that fell to Earth

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Two wayward space rocks, which separately crashed to Earth in 1998 after circulating in our solar system’s asteroid belt for billions of years, share something else in common: the ingredients for life. They are the first meteorites found to contain both liquid water and a mix of complex organic compounds such as hydrocarbons and amino acids.

A detailed study of the chemical makeup within tiny blue and purple salt crystals sampled from these meteorites, which included results from X-ray experiments at the Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab), also found evidence for the pair’s past intermingling and likely parents. These include Ceres, a brown dwarf planet that is the largest object in the asteroid belt, and the asteroid Hebe, a major source of meteorites that fall on Earth.

https://astronomynow.com/2018/01/16/ingredients-for-life-revealed-in-meteorites-that-fell-to-earth/

I'm pretty sure I remember a while back reading about water from the ancient Earth discovered in salt crystals from fossilized rocks... ah, here it is!

https://www.sciencedaily.com/releases/2001/12/011210163624.htm

This new study looks to be in a similar spirit.  (Boy, it really WAS a while back!)  Awfully interesting stuff.
Post by: Star One on 01/17/2018 08:11 PM
The Third Workshop on Extremely Precise Radial Velocities: The New Instruments

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The Third Workshop on Extremely Precise Radial Velocities was held at the Penn Stater Conference Center and Hotel in State College, Pennsylvania, USA from 2016 August 14 to 17, and featured over 120 registrants from around the world. Here we provide a brief description of the conference, its format, and its session topics and chairs. 23 instrument teams were represented in plenary talks, and we present a table containing the basic characteristics of their new precise Doppler velocimeters.

https://arxiv.org/abs/1801.05383
Post by: Star One on 01/18/2018 07:33 PM
Using Gravitational-wave Observations and Quasi-universal Relations to Constrain the Maximum Mass of Neutron Stars

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Combining the GW observations of merging systems of binary neutron stars and quasi-universal relations, we set constraints on the maximum mass that can be attained by nonrotating stellar models of neutron stars. More specifically, exploiting the recent observation of the GW event GW170817 and drawing from basic arguments on kilonova modeling of GRB 170817A together with the quasi-universal relation between the maximum mass of nonrotating stellar models ${M}_{\mathrm{TOV}}$ and the maximum mass supported through uniform rotation ${M}_{\max }\,=({1.20}_{-0.05}^{+0.02}){M}_{\mathrm{TOV}}$, we set limits for the maximum mass to be ${2.01}_{-0.04}^{+0.04}\leqslant {M}_{\mathrm{TOV}}/{M}_{\odot }\lesssim {2.16}_{-0.15}^{+0.17}$, where the lower limit in this range comes from pulsar observations. Our estimate, which follows a very simple line of arguments and does not rely on the modeling of the electromagnetic signal in terms of numerical simulations, can be further refined as new detections become available. We briefly discuss the impact that our conclusions have on the equation of state of nuclear matter.

http://iopscience.iop.org/article/10.3847/2041-8213/aaa401/meta

New Titan Findings from Topographical Map

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Cassini’s huge dataset will yield discoveries for many years, as witness the global topographical map of Titan that has been assembled by Cornell University astronomers. The map draws on topographical data of the moon from multiple sources by way of studying its terrain and the flow of its surface liquids. Bear in mind that only 9 percent of Titan has been observed at relatively high resolution, and another 25-30 percent at lower resolution. For the remainder, the team mapped the surface using an interpolation algorithm and a global minimization process described in the first of two papers in Geophysical Review Letters.

https://www.centauri-dreams.org/?p=39157
Post by: jebbo on 01/19/2018 07:57 AM
Interesting proposal for a large space-based telescope to hunt for biosignatures ... this is the first ESA L4 idea I've seen (might be premature to create an ESA L4 mission competition thread ;) )

Personally, in that time frame, I'd be thinking about on-orbit assembly rather than single fairing-limited launch.

SUPERSHARP - Segmented Unfolding Primary for Exoplanet Research via Spectroscopic High Angular Resolution Photography

Quote
We propose to search for biosignatures in the spectra of reflected light from about 100 Earth-sized planets that are already known to be orbiting in their habitable zones (HZ). For a sample of G and K type hosts, most of these planets will be between 25 and 50 milli-arcsec (mas) from their host star and 1 billion to 10 billion times fainter. To separate the planet's image from that of its host star at the wavelength (763nm) of the oxygen biosignature we need a telescope with an aperture of 16 metres. Furthermore, the intensity of the light from the host star at the position in the image of the exoplanet must be suppressed otherwise the exoplanet will be lost in the glare.
This presents huge technical challenges. The Earth's atmosphere is turbulent which makes it impossible to achieve the required contrast from the ground at 763nm. The telescope therefore needs to be in space and to fit the telescope in the rocket fairing it must be a factor of 4 or more times smaller when folded than when operational. To obtain spectroscopy of the planet's biosignature at 763nm we need to use an integral field spectrometer (IFS) with a field of view (FOV) of 1000 x 1000 milli-arcsec (mas) and a spectral resolution of 100. This is a device that simultaneously takes many pictures of the exoplanet each at a slightly different wavelength which are then recorded as a data cube with two spatial dimensions and one wavelength dimension. In every data cube wavelength slice, the background light from the host star at the location of the planet image must be minimised. This is achieved via a coronagraph which blocks the light from the host star and active/adaptive optics techniques which continuously maintain very high accuracy optical alignment to make the images as sharp as possible. These are the technical challenges to be addressed in a design study.

https://arxiv.org/abs/1801.06111 (https://arxiv.org/abs/1801.06111)

--- Tony
Post by: Star One on 01/19/2018 08:48 PM
Neutron star merger yields new puzzle for astrophysicists

https://astronomynow.com/2018/01/19/neutron-star-merger-yields-new-puzzle-for-astrophysicists/
Post by: Star One on 01/23/2018 08:06 PM
Evidence of an Upper Bound on the Masses of Planets and Its Implications for Giant Planet Formation

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Celestial bodies with a mass of $M\approx 10\,{M}_{\mathrm{Jup}}$ have been found orbiting nearby stars. It is unknown whether these objects formed like gas-giant planets through core accretion or like stars through gravitational instability. I show that objects with $M\lesssim 4\,{M}_{\mathrm{Jup}}$ orbit metal-rich solar-type dwarf stars, a property associated with core accretion. Objects with $M\gtrsim 10\,{M}_{\mathrm{Jup}}$ do not share this property. This transition is coincident with a minimum in the occurrence rate of such objects, suggesting that the maximum mass of a celestial body formed through core accretion like a planet is less than $10\,{M}_{\mathrm{Jup}}$. Consequently, objects with $M\gtrsim 10\,{M}_{\mathrm{Jup}}$ orbiting solar-type dwarf stars likely formed through gravitational instability and should not be thought of as planets. Theoretical models of giant planet formation in scaled minimum-mass solar nebula Shakura–Sunyaev disks with standard parameters tuned to produce giant planets predict a maximum mass nearly an order of magnitude larger. To prevent newly formed giant planets from growing larger than $10\,{M}_{\mathrm{Jup}}$, protoplanetary disks must therefore be significantly less viscous or of lower mass than typically assumed during the runaway gas accretion stage of giant planet formation. Either effect would act to slow the Type I/II migration of planetary embryos/giant planets and promote their survival. These inferences are insensitive to the host star mass, planet formation location, or characteristic disk dissipation time.

http://iopscience.iop.org/article/10.3847/1538-4357/aa961c

Medium-sized satellites of large Kuiper belt objects

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While satellites of mid- to small-Kuiper belt objects tend to be similar in size and brightness to their primaries, the largest Kuiper belt objects preferentially have satellites with small fractional brightness. In the two cases where the sizes and albedos of the small faint satellites have been measured, these satellites are seen to be small icy fragments consistent with collisional formation. Here we examine Dysnomia and Vanth, the satellites of Eris and Orcus, respectively. Using the Atacama Large Millimeter Array, we obtain the first spatially resolved observations of these systems at thermal wavelengths. We find a diameter for Dysnomia of 700±115 km and for Vanth of 475+/-75 km, with albedos of 0.04_+0.02_-0.01 and 0.08+/-0.02 respectively. Both Dysnomia and Vanth are indistinguishable from typical Kuiper belt objects of their size. Potential implications for the formation of these types of satellites are discussed.

https://arxiv.org/abs/1801.07221
Post by: Star One on 01/24/2018 04:51 PM
Really like Phil Plait’s writing on this article, he has a really good way of getting things across.

THE STAR HD 4113 IS WAY, *WAY* MORE THAN MEETS THE EYE

http://www.syfy.com/syfywire/the-star-hd-4113-is-way-way-more-than-meets-the-eye
Post by: jebbo on 01/24/2018 05:00 PM
Lol, I'm not a huge fan of his style .. all the gosh wow stuff irritates me. But he does explain things well.

Edit: though I must say HD 4113 deserves the odd gosh, wow ;-)

--- Tony
Post by: Star One on 01/24/2018 07:58 PM
Lol, I'm not a huge fan of his style .. all the gosh wow stuff irritates me. But he does explain things well.

Edit: though I must say HD 4113 deserves the odd gosh, wow ;-)

--- Tony

He’s not writing to an informed audience such as yourself but rather Joe Public.
Post by: CuddlyRocket on 01/24/2018 08:05 PM
Lol, I'm not a huge fan of his style .. all the gosh wow stuff irritates me. But he does explain things well.

Edit: though I must say HD 4113 deserves the odd gosh, wow ;-)

--- Tony

He’s not writing to an informed audience such as yourself but rather Joe Public.

I'd still rather he'd get the distinction between a name and a designation right (HD 4113 is a designation, not a name). It's a minor thing but it's often those little niggles that annoy! :)
Post by: Star One on 01/24/2018 08:15 PM
More about the TRAPPIST-1 system from a new paper.

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And while we’re talking about M-dwarfs, a new paper is out looking at one of the most interesting systems yet discovered, comprising the seven planets around TRAPPIST-1. Lead author Amy Barr (Planetary Science Institute) and colleagues go to work on the interior structures of these planets as well as their tidal heating and convection given what we know about their mass and radius. The balance between tidal heating and convective transport has implications for the mantles of each planet.

https://www.centauri-dreams.org/?p=39185
Post by: Star One on 01/24/2018 08:47 PM
Astronomers produce first detailed images of surface of giant star

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ATLANTA -- An international team of astronomers has produced the first detailed images of the surface of a giant star outside our solar system, revealing a nearly circular, dust-free atmosphere with complex areas of moving material, known as convection cells or granules, according to a recent study.

The giant star, named π1Gruis, is one of the stars in the constellation Grus (Latin for the crane, a type of bird), which can be observed in the southern hemisphere. An evolved star in the last major phase of life, π1Gruis is 350 times larger than the Sun and resembles what our Sun will become at the end of its life in five billion years. Studying this star gives scientists insight about the future activity, characteristics and appearance of the Sun.

Post by: Star One on 01/25/2018 08:06 PM
NASA Poised to Topple a Planet-Finding Barrier

NASA optics experts are well on the way to toppling a barrier that has thwarted scientists from achieving a long-held ambition: building an ultra-stable telescope that locates and images dozens of Earth-like planets beyond the solar system and then scrutinizes their atmospheres for signs of life.

Babak Saif and Lee Feinberg at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, have shown for the first time that they can dynamically detect subatomic- or picometer-sized distortions — changes that are far smaller than an atom — across a five-foot segmented telescope mirror and its support structure. Collaborating with Perry Greenfield at the Space Telescope Science Institute in Baltimore, the team now plans to use a next-generation tool and thermal test chamber to further refine their measurements.

The measurement feat is good news to scientists studying future missions for finding and characterizing extrasolar Earth-like planets that potentially could support life.

To find life, these observatories would have to gather and focus enough light to distinguish the planet’s light from that of its much brighter parent star and then be able to dissect that light to discern different atmospheric chemical signatures, such as oxygen and methane. This would require a super-stable observatory whose optical components move or distort no more than 12 picometers, a measurement that is about one-tenth the size of a hydrogen atom.

To date, NASA has not built an observatory with such demanding stability requirements.

How Displacements Occur

Displacements and movement occur when materials used to build telescopes shrink or expand due to wildly fluctuating temperatures, such as those experienced when traveling from Earth to the frigidity of space, or when exposed to fierce launch forces more than six-and-a-half times the force of gravity.

Scientists say that even nearly imperceptible, atomic-sized movements would affect a future observatory’s ability to gather and focus enough light to image and analyze the planet’s light. Consequently, mission planners must design telescopes to picometer accuracies and then test it at the same level across the entire structure, not just between the telescope’s reflective mirrors. Movement occurring at any particular position might not accurately reflect what’s actually happening in other locations.

“These future missions will require an incredibly stable observatory,” said Azita Valinia, deputy Astrophysics Projects Division program manager. “This is one of the highest technology tall poles that future observatories of this caliber must overcome. The team’s success has shown that we are steadily whittling away at that particular obstacle.”

The Initial Test

To carry out the test, Saif and Feinberg used the High-Speed Interferometer, or HSI — an instrument that the Arizona-based 4D Technology developed to measure nanometer-sized dynamic changes in the James Webb Space Telescope’s optical components — including its 18 mirror segments, mounts, and other supporting structures —  during thermal, vibration and other types of environmental testing.

Like all interferometers, the instrument splits light and then recombines it to measure tiny changes, including motion. The HSI can quickly measure dynamic changes across the mirror and other structural components, giving scientists insights into what is happening all across the telescope, not just in one particular spot.

Even though the HSI was designed to measure nanometer or molecule-sized distortions — which was the design standard for Webb — the team wanted to see it could use the same instrument, coupled with specially developed algorithms, to detect even smaller changes over the surface of a spare five-foot Webb mirror segment and its support hardware.

The test proved it could, measuring dynamic movement as small as 25 picometers — about twice the desired target, Saif said.

Next Steps

However, Goddard and 4D Technology have designed a new high-speed instrument, called a speckle interferometer, that allows measurements of both reflective and diffuse surfaces at picometer accuracies. 4D Technology has built the instrument and the Goddard team has begun initial characterization of its performance in a new thermal-vacuum test chamber that controls internal temperatures to a frosty 1-millikelvin.

Saif and Feinberg plan to place test items inside the chamber to see if they can achieve the 12-picometer target accuracy.

“I think we’ve made a lot of progress. We’re getting there,” Saif said.

For more Goddard technology news, go to https://www.nasa.gov/sites/default/files/atoms/files/
Post by: Star One on 01/27/2018 09:10 PM
Exocomets

Friday, January 26, 2018

Quote
Science Update - A look at CfA discoveries from recent journals
There are currently over 3500 confirmed exoplanets known thanks to the remarkable sensitivity of the Kepler spacecraft and to technological advances in space and ground-based methods made over the past dozen years. Relatively little is known, however, about the minor bodies that might orbit within these systems, asteroids and comets for example. Planet-formation theories predict that such minor bodies should be common, but their low masses and small radii present extreme detection challenges. Methods that rely on solid body transits or velocity variations are generally orders-of-magnitude too weak to spot such small objects. The smallest solid body that has been detected so far via the transit method is an object about one-quarter the size of the Earth, while pulsar timing measurements have spotted a lunar-mass object orbiting a pulsar.

In a tour de force analysis of the Kepler data sets spanning 201250 target stars, CfA astronomers Andrew Vanderburg, Dave Latham, and Allyson Bieryla joined eight of their colleagues in discovering and modeling a likely set of six transiting comets around one star, with another comet possible around a second star. The physical characteristic that made these detections possible was unexpected: the comets have large, extended dust tails that can block enough starlight to make themselves recognizable via unique, asymmetrically shaped absorption dips in their transit lightcurves. (The paper reports, in press, finding a prediction of just such an effect published in 1999). The astronomers systematically consider other explanations for the dips, including starspots, as well as possible inconsistencies in their cometary model, like orbital behavior, but reject them all.

The scientists can estimate the mass of the comets from the observed transit properties and simple assumptions, and they conclude that the bodies are probably similar in mass to Halley's Comet. The scientists also conclude that exocomets are probably not rare given that these seven were spotted without using sophisticated computer tools, although deeper searches will need to be undertaken to find them. Since the two stars hosting exocomets in their study are quite similar in type, they conclude by wondering whether comet transits happen preferentially around certain kinds of stars, although why this might be is not known.

https://www.cfa.harvard.edu/news/su201804
Post by: Hog on 01/29/2018 07:32 PM
Super Blue Blood Moon is scheduled for the Moonrise of the morning of Jan 31st, 2018.

This event wont happen for another 150 years.

It's a Super Moon as it is closer and will appear larger by 14%.  It's a Blue Moon as it is the 2nd full Moon of a calendar month.  And it will appear Red as it all occurring during a Lunar eclipse.

https://www.nasa.gov/feature/super-blue-blood-moon-coming-jan-31
Post by: Star One on 01/29/2018 07:37 PM
The Likelihood of Massive Exomoons

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Are there large moons — perhaps Earth-sized or even bigger — around gas giant planets in habitable zones somewhere in the Milky Way? It’s a wonderful thought given how it multiplies the opportunities for life to find a foothold even in systems much different from our own. Centauri Dreams regular Andrew Tribick recently passed along a new paper that addresses the question in an interesting way, by modeling moon formation and orbital evolution under widely varying conditions of circumplanetary disk composition and evolution.

https://www.centauri-dreams.org/?p=39214
Post by: Star One on 01/30/2018 07:42 PM
HD 4915: A Maunder Minimum Candidate

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We study the magnetic activity cycle of HD 4915 using the \ion{Ca}{2} H \& K emission line strengths measured by Keck I/HIRES spectrograph. The star has been observed as a part of California Planet Search Program from 2006 to present. We note decreasing amplitude in the magnetic activity cycle, a pattern suggesting the star's entry into a Magnetic Grand Minimum (MGM) state, reminiscent of the Sun's Maunder and Dalton Minima. We recommend further monitoring of the star to confirm the grand minimum nature of the dynamo, which would provide insight into the state of the Sun's chromosphere and the global magnetic field during its grand minima. We also recommend continued observations of H \& K emission lines, and ground or space based photometric observations to estimate the sunspot coverage.

https://arxiv.org/abs/1801.09650
Post by: Star One on 02/01/2018 07:41 PM
2004 EW95: A phyllosilicate bearing carbonaceous asteroid in the Kuiper Belt

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Models of the Solar System's dynamical evolution predict the dispersal of primitive planetesimals from their formative regions amongst the gas-giant planets due to the early phases of planetary migration. Consequently, carbonaceous objects were scattered both into the outer asteroid belt and out to the Kuiper Belt. These models predict that the Kuiper Belt should contain a small fraction of objects with carbonaceous surfaces, though to date, all reported visible reflectance spectra of small Kuiper Belt Objects (KBOs) are linear and featureless. We report the unusual reflectance spectrum of a small KBO, (120216) 2004 EW95, which exhibits a large drop in its near-UV reflectance and a broad shallow optical absorption feature centered at ~700 nm. These features, confirmed through multiple epochs of spectral photometry and spectroscopy, have respectively been associated with ferric oxides and phyllosilicates. The spectrum bears striking resemblance to those of some C-type asteroids, suggesting that those objects may share a common origin with 2004 EW95. 2004 EW95 orbits the Sun in a stable mean motion resonance with Neptune, at relatively high eccentricity and inclination, suggesting it may have been emplaced there by some past dynamical instability. These results appear consistent with the aforementioned model predictions and are the first to show a reliably confirmed detection of silicate material on a small KBO.

https://arxiv.org/abs/1801.10163 (https://arxiv.org/abs/1801.10163)

Normal black holes in bulge-less galaxies: the largely quiescent, merger-free growth of black holes over cosmic time

Quote
Understanding the processes that drive the formation of black holes (BHs) is a key topic in observational cosmology. While the observed MBH--MBulge correlation in bulge-dominated galaxies is thought to be produced by major mergers, the existence of a MBH--M⋆ relation, across all galaxy morphological types, suggests that BHs may be largely built by secular processes. Recent evidence that bulge-less galaxies, which are unlikely to have had significant mergers, are offset from the MBH--MBulge relation, but lie on the MBH--M⋆ relation, has strengthened this hypothesis. Nevertheless, the small size and heterogeneity of current datasets, coupled with the difficulty in measuring precise BH masses, makes it challenging to address this issue using empirical studies alone. Here, we use Horizon-AGN, a cosmological hydrodynamical simulation to probe the role of mergers in BH growth over cosmic time. We show that (1) as suggested by observations, simulated bulge-less galaxies lie offset from the main MBH--MBulge relation, but on the MBH--M⋆ relation, (2) the positions of galaxies on the MBH--M⋆ relation are not affected by their merger histories and (3) only ∼35 per cent of the BH mass in today's massive galaxies is directly attributable to merging -- the majority (∼65 per cent) of BH growth, therefore, takes place gradually, via secular processes, over cosmic time.

https://arxiv.org/abs/1801.09699 (https://arxiv.org/abs/1801.09699)
Post by: Star One on 02/01/2018 07:58 PM
Astronomers Find One of the Oldest Stars in the Milky Way

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The formation of the first stars was also what allowed for the creation of heavier elements, and therefore the formation of planets and all life as we know it. However, until now, how and when this process took place has been largely theoretical since astronomers did not know where the oldest stars in our galaxy were to be found. But thanks to a new study by a team of Spanish astronomers, we may have just found the oldest star in the Milky Way!

https://www.universetoday.com/138450/astronomers-find-one-oldest-stars-milky-way/amp/
Post by: Star One on 02/05/2018 05:45 PM
Amazing to detect planets in another galaxy over such a vast distance.

OU Astrophysicists Discover Planets in Extragalactic Galaxies

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NORMAN — A University of Oklahoma astrophysics team has discovered for the first time a population of planets beyond the Milky Way galaxy. Using microlensing—an astronomical phenomenon and the only known method capable of discovering planets at truly great distances from the Earth among other detection techniques—OU researchers were able to detect objects in extragalactic galaxies that range from the mass of the Moon to the mass of Jupiter.

Xinyu Dai, professor in the Homer L. Dodge Department of Physics and Astronomy, OU College of Arts and Sciences, with OU postdoctoral researcher Eduardo Guerras, made the discovery with data from the National Aeronautics and Space Administration’s Chandra X-ray Observatory, a telescope in space that is controlled by the Smithsonian Astrophysical Observatory.

“We are very excited about this discovery. This is the first time anyone has discovered planets outside our galaxy,” said Dai. “These small planets are the best candidate for the signature we observed in this study using the microlensing technique. We analyzed the high frequency of the signature by modeling the data to determine the mass.”

While planets are often discovered within the Milky Way using microlensing, the gravitational effect of even small objects can create high magnification leading to a signature that can be modeled and explained in extragalactic galaxies. Until this study, there has been no evidence of planets in other galaxies.

“This is an example of how powerful the techniques of analysis of extragalactic microlensing can be. This galaxy is located 3.8 billion light years away, and there is not the slightest chance of observing these planets directly, not even with the best telescope one can imagine in a science fiction scenario,” said Guerras. “However, we are able to study them, unveil their presence and even have an idea of their masses. This is very cool science.”

For this study, OU researchers used the NASA Chandra X-ray Observatory at the Smithsonian Astrophysical Observatory. The microlensing models were calculated at the OU Supercomputing Center for Education and Research.

A paper, “Probing Planets in Extragalactic Galaxies Using Quasar Microlensing,” by Dai and Guerras on this study has been published in the Astrophysical Journal Letters. For more information about this research, contact OU Professor Dai at [email protected]

http://ou.edu/publicaffairs/archives/2018/OUAstrophysictsDiscoverPlanetsinExtragalacticGalaxies.html

Probing Planets in Extragalactic Galaxies Using Quasar Microlensing

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Previously, planets have been detected only in the Milky Way galaxy. Here, we show that quasar microlensing provides a means to probe extragalactic planets in the lens galaxy, by studying the microlensing properties of emission close to the event horizon of the supermassive black hole of the background quasar, using the current generation telescopes. We show that a population of unbound planets between stars with masses ranging from Moon to Jupiter masses is needed to explain the frequent Fek line energy shifts observed in the gravitationally lensed quasar RXJ1131-1231 at a lens redshift of z=0.295 or 3.8 billion light-years away. We constrain the planet mass fraction to be larger than 0.0001 of the halo mass, which is equivalent to 2,000 objects ranging from Moon to Jupiter mass per main sequence star.

https://arxiv.org/abs/1802.00049
Post by: Star One on 02/07/2018 05:15 PM
TRAPPIST-1: Planets Likely Rich in Volatiles

https://www.centauri-dreams.org/2018/02/07/trappist-1-planets-likely-rich-in-volatiles/
Post by: CuddlyRocket on 02/08/2018 10:43 PM
Magellan/PFS Radial Velocities of GJ 9827, a late K dwarf at 30 pc with Three Transiting Super-Earths (https://arxiv.org/abs/1711.01359) (arXiv)

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(Abstract) The Kepler mission showed us that planets with sizes between that of Earth and Neptune appear to be the most common type in our Galaxy. These "super-Earths" continue to be of great interest for exoplanet formation, evolution, and composition studies. However, the number of super-Earths with well-constrained mass and radius measurements remains small (40 planets with σmass< 25\%), due in part to the faintness of their host stars causing ground-based mass measurements to be challenging. Recently, three transiting super-Earth planets were detected by the K2 mission around the nearby star GJ 9827/HIP 115752, at only 30 pc away. The radii of the planets span the "radius gap"' detected by Fulton et al. (2017), and all orbit within ~6.5 days, easing follow-up observations. Here we report radial velocity (RV) observations of GJ 9827, taken between 2010 and 2016 with the Planet Finder Spectrograph on the Magellan II Telescope. We employ two different RV analysis packages, SYSTEMIC and RadVel, to derive masses and thus densities of the GJ 9827 planets. We also test a Gaussian Process regression analysis, but find the correlated stellar noise is not well constrained by the PFS data, and that the GP tends to over fit the RV semi-amplitudes resulting in a lower K value. Our RV observations are not able to place strong mass constraints on the two outer planets (c & d) but do indicate that planet b, at 1.64 R⊕ and ~8 M⊕, is one of the most massive (and dense) super-Earth planets detected to date.
Post by: Star One on 02/13/2018 08:35 PM
Formation of the Earth's inner core is so baffling, scientists say it shouldn't exist

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According to the popular view of the Earth's formation, about one billion years ago, our planet's molten liquid inner core spontaneously began to crystallise, growing rapidly to the extent that it reaches today – around 760 miles in diameter.

However, a new study published in the journal Earth and Planetary Science Letters contradicts this theory, suggesting it is impossible.

http://www.ibtimes.co.uk/formation-earths-inner-core-so-baffling-scientists-say-it-shouldnt-exist-1661119
Post by: Star One on 02/15/2018 07:58 PM
Milky Way no longer ‘little brother’ to Andromeda

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Using a new technique to assess the mass of the Andromeda galaxy, researchers have concluded the giant spiral is not so much a big brother to the Milky Way as it is a near twin.

It has long been thought that Andromeda was two to three times the size of the Milky Way and that Earth’s galaxy would eventually be engulfed during a gravitational close encounter in 5 billion years or so.

https://astronomynow.com/2018/02/15/milky-way-no-longer-little-brother-to-andromeda-researchers-say/
Post by: Star One on 02/15/2018 08:09 PM
Supermassive black hole model predicts characteristic light signals at cusp of collision

A new simulation of supermassive black holes--the behemoths at the centers of galaxies--uses a realistic scenario to predict the light signals emitted in the surrounding gas before the masses collide, said Rochester Institute of Technology researchers.

The RIT-led study represents the first step toward predicting the approaching merger of supermassive black holes using the two channels of information now available to scientists--the electromagnetic and the gravitational wave spectra--known as multimessenger astrophysics. The findings appear in the paper "Quasi-periodic Behavior of Mini-disks in Binary Black Holes Approaching Merger," published in the Astrophysical Journal Letters.

"We've performed the first simulation in which an accretion disk around a binary black hole feeds individual accretion disks, or mini-disks, around each black hole in general relativity and magnetohydrodynamics," said Dennis Bowen, lead author and postdoctoral researcher at RIT's Center for Computational Relativity and Gravitation.

Unlike their less massive cousins, first detected in 2016, supermassive black holes are fed by gas disks that surround them like doughnuts. The strong gravitational pull of the black holes that inspiral toward one another heats and disrupts the flow of gas from disk to black hole and emits periodic signals in the visible to X-ray portions of the electromagnetic spectrum.

"We have not yet seen two supermassive black holes get this close," Bowen said. "It provides the first hints of what these mergers will look like in a telescope. The filling and refilling of mini-disks affect the light signatures."

The simulation models supermassive black holes in a binary pair, each surrounded by its own gas disks. A much larger gas disk encircles the black holes and disproportionately feeds one mini-disk over another, leading to the filling-and-refilling cycle described in the paper.

"The evolution is long enough to study what the real science outcome would look like," said Manuela Campanelli, director of the Center for Computational Relativity and Gravitation and a co-author on the paper.

Binary supermassive black holes emit gravitational waves at lower frequencies than stellar-mass black holes. The ground-based Laser Interferometer Gravitational-wave Observatory, in 2016, detected the first gravitational waves from stellar mass black holes collisions with an instrument tuned to higher frequencies. LIGO's sensitivity is unable to observe the gravitational wave signals produced by supermassive black hole coalescence.

The launch of the space-based Laser Interferometer Space Antenna, or LISA, slated for the 2030s, will detect gravitational waves from colliding supermassive black holes in the cosmos. When operational in the 2020s, the ground-based Large Synoptic Survey Telescope, or LSST, under construction in Cerro Pachón, Chile, will produce the widest, deepest survey of light emissions in the universe. The pattern of signals predicted in the RIT study could guide scientists to orbiting pairs of supermassive black holes.

"In the era of multimessenger astrophysics, simulations such as this are necessary to make direct predictions of electromagnetic signals that will accompany gravitational waves," Bowen said. "This is the first step toward the ultimate goal of simulations capable of making direct predictions of the electromagnetic signal from binary black holes approaching merger."

Bowen and his collaborators combined simulations from RIT's Black Hole Lab computer clusters and the Blue Waters supercomputer at the National Center for Supercomputing Applications at the University of Illinois at Urbana-Champaign, one of the largest supercomputers in the United States.

Astrophysicists from RIT, Johns Hopkins University and NASA Goddard Space Flight Center collaborated on the project. The publication is based on Bowen's Ph.D. dissertation at RIT and completes research begun by a co-author, Scott Noble, a former RIT post-doctoral researcher, now at NASA Goddard. Their research is part of a collaborative National Science Foundation-funded project led by Campanelli. Co-authors include Vassilios Mewes, RIT postdoctoral researcher; Miguel Zilhao, former RIT post-doctoral researcher, now at Universidade de Lisboa, in Portugal; and Julian Krolik, professor of physics and astronomy at Johns Hopkins University.

In an upcoming paper, the authors will explore further the correlation between gas flowing in and out of the accretion disks and fluctuating light emissions. They will present predictions of light signatures scientists can expect to see with advanced telescopes when looking for supermassive black holes approaching merger.

Post by: Star One on 02/16/2018 07:54 PM
New research note.

No Giant Planet Pileup Near 1 au

http://iopscience.iop.org/article/10.3847/2515-5172/aaaebd/meta

Discovery of a Magnetic White Dwarf with Unusual Short-period Variability

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We report the discovery of a magnetic white dwarf which shows periodic variability with P = 110 minutes, color-dependent amplitudes and a transient phase shift in the blue compared to the red lightcurve—a previously unknown type of variability for this type of object. We attribute the variations either to a close ultracool (thus far undetected) companion or, more likely, to magnetic spots with unusual temperature structure.

The object SDSS 160357.93+140929.97 (hereafter SDSS 16+14) was identified as a magnetic white dwarf in Kepler et al. (2013), with an effective temperature of 10,123 K ands a magnetic field strength of 43 MG. We monitored this target on 2015 May 3 and June 5, each time over a time period of 3 hr, using the optical camera EFOSC2 at the ESO/NTT (program 095.D-0245). The g-band lightcurves shows a photometric period of ~100 minutes, with a min–max amplitude of ~3% (compared to a photometric noise of 1%–2%).7

Post by: Star One on 02/19/2018 08:23 PM
The starry sky shows nocturnal animals the way

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Nocturnal animals can use the stars and the Milky Way to find their way during the darkest hours. While animal navigation is studied all over the world, some of the leading researchers are based at Lund University in Sweden. In a recent article they sum up the research so far and give their thoughts on challenges to come.

https://www.lunduniversity.lu.se/article/the-starry-sky-shows-nocturnal-animals-the-way
Post by: Star One on 02/20/2018 07:44 PM
Astronomers Observe The Rotating Accretion Disk Around The Supermassive Black Hole In M77

https://www.universetoday.com/138589/astronomers-observe-rotating-accretion-disk-around-supermassive-black-hole-m77/
Post by: Star One on 02/22/2018 08:47 AM
An amateur astronomer accidentally caught an exploding star on camera—and it gets better

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Victor Buso was looking forward to testing his new camera on September 20, 2016. The locksmith and amateur astronomer waited for nightfall and headed out to his rooftop observatory in the city of Rosario, Argentina, where his 15.7 inch (40 cm) Newtonian telescope was waiting. He had no idea he would help capture the start of one of the most unpredictable events in the universe; a supernova.

https://www.popsci.com/amateur-astronomer-photographs-birth-supernova
Post by: IRobot on 02/22/2018 10:33 AM
An amateur astronomer accidentally caught an exploding star on camera—and it gets better

Having worked for several years in the "amateur" astronomy market making CCD cameras, I find it harder and harder to call these people "amateurs". Especially one like this, owning a 16inch scope.
They spend tens of thousands of dollars, sometimes hundreds of thousands of dollars and they make some remarkable things, considering that they are not working full time, most of them don't have the technical or theoretical background and they work most of the times from sub urban locations.

I even know some who do yearly calibrations of professional telescopes!

Among several achievements, they have done:
- discoveries of supernovas
- discoveries of exoplanets
- discoveries of nebulae or nebulae sub-structures
- rocket launch and satellite tracking
- long lost IMAGE sattelite
- independent confirmations of known phenomenons

The last point is important. One argument against conspiracy theories (flat earth, moon landing deniers, UFOs,...) is that amateur astronomers, being independent, keep disproving these wacky theories.
Post by: Star One on 02/22/2018 07:36 PM
Studying the Ultraviolet Spectrum of the First Spectroscopically Confirmed Supernova at Redshift Two

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Abstract
We present observations of DES16C2nm, the first spectroscopically confirmed hydrogen-free superluminous supernova (SLSN-I) at redshift $z\approx 2$. DES16C2nm was discovered by the Dark Energy Survey (DES) Supernova Program, with follow-up photometric data from the Hubble Space Telescope, Gemini, and the European Southern Observatory Very Large Telescope supplementing the DES data. Spectroscopic observations confirm DES16C2nm to be at z = 1.998, and spectroscopically similar to Gaia16apd (a SLSN-I at z = 0.102), with a peak absolute magnitude of $U=-22.26\pm 0.06$. The high redshift of DES16C2nm provides a unique opportunity to study the ultraviolet (UV) properties of SLSNe-I. Combining DES16C2nm with 10 similar events from the literature, we show that there exists a homogeneous class of SLSNe-I in the UV (${\lambda }_{\mathrm{rest}}\approx 2500$ Å), with peak luminosities in the (rest-frame) U band, and increasing absorption to shorter wavelengths. There is no evidence that the mean photometric and spectroscopic properties of SLSNe-I differ between low ($z\lt 1$) and high redshift ($z\gt 1$), but there is clear evidence of diversity in the spectrum at ${\lambda }_{\mathrm{rest}}\lt 2000\,\mathring{\rm A}$, possibly caused by the variations in temperature between events. No significant correlations are observed between spectral line velocities and photometric luminosity. Using these data, we estimate that SLSNe-I can be discovered to z = 3.8 by DES. While SLSNe-I are typically identified from their blue observed colors at low redshift ($z\lt 1$), we highlight that at $z\gt 2$ these events appear optically red, peaking in the observer-frame z-band. Such characteristics are critical to identify these objects with future facilities such as the Large Synoptic Survey Telescope, Euclid, and the Wide-field Infrared Survey Telescope, which should detect such SLSNe-I to z = 3.5, 3.7, and 6.6, respectively.

http://iopscience.iop.org/article/10.3847/1538-4357/aaa126/meta
Post by: Star One on 02/22/2018 08:23 PM
Some black holes erase your past

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In the real world, your past uniquely determines your future. If a physicist knows how the universe starts out, she can calculate its future for all time and all space.

But a UC Berkeley mathematician has found some types of black holes in which this law breaks down. If someone were to venture into one of these relatively benign black holes, they could survive, but their past would be obliterated and they could have an infinite number of possible futures.

http://news.berkeley.edu/2018/02/20/some-black-holes-erase-your-past/
Post by: eeergo on 02/24/2018 12:14 PM
https://www.nature.com/articles/nature25151

An "amateur" Argentinian astronomer from Rosario has observed, for the first time, the start of a supernova (IIb) explosion, confirming theoretical models.

Post by: Star One on 02/25/2018 08:21 AM
https://www.nature.com/articles/nature25151

An "amateur" Argentinian astronomer from Rosario has observed, for the first time, the start of a supernova (IIb) explosion, confirming theoretical models.

See post #341 in this thread.
Post by: missinglink on 02/26/2018 08:33 AM
Formation of the Earth's inner core is so baffling, scientists say it shouldn't exist

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According to the popular view of the Earth's formation, about one billion years ago, our planet's molten liquid inner core spontaneously began to crystallise, growing rapidly to the extent that it reaches today – around 760 miles in diameter.

However, a new study published in the journal Earth and Planetary Science Letters contradicts this theory, suggesting it is impossible.

http://www.ibtimes.co.uk/formation-earths-inner-core-so-baffling-scientists-say-it-shouldnt-exist-1661119
Only one way to settle this once and for all ... a giant power drill made of pure diamond to carry a determined crew into the beating heart of the planet ... and back out again on the other side.
Post by: Star One on 02/27/2018 08:13 PM
These results seemingly confirm that the expansion of the universe has accelerated since its early days.

Precise New Measurements From Hubble Confirm the Accelerating Expansion of the Universe. Still no Idea Why it’s Happening

https://www.universetoday.com/138663/precise-new-measurements-hubble-confirm-accelerating-expansion-universe-still-no-idea-happening/amp/

Beaming with the Light of Millions of Suns

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In the 1980s, researchers began discovering extremely bright sources of X-rays in the outer portions of galaxies, away from the supermassive black holes that dominate their centers. At first, the researchers thought these cosmic objects—called ultraluminous X-ray sources, or ULXs—were hefty black holes with more than 10 times the mass of the sun. But observations beginning in 2014 from NASA's NuSTAR (Nuclear Spectroscopic Telescope Array) and other space telescopes are showing that some ULXs, which glow with X-ray light equal in energy to millions of suns, are actually neutron stars—the burnt-out cores of massive stars that exploded. Three such ULXs have been identified as neutron stars so far.

http://m.caltech.edu/news/beaming-light-millions-suns-81447

When do aging brown dwarfs sweep the clouds away?

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Astronomers measure temperature at which brown dwarfs go from cloudy to cloudless

Post by: Star One on 02/28/2018 07:51 PM
It’s not often that an astronomy story is the headline news story on a UK national newspaper website. Even a broadsheet like The Guardian.

Cosmic dawn: astronomers detect signals from first stars in the universe

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’Revolutionary’ observations suggest the first stars appeared 180m years after the big bang – and may hold information on dark matter

https://www.theguardian.com/science/2018/feb/28/cosmic-dawn-astronomers-detect-signals-from-first-stars-in-the-universe

And here’s the relevant paper.

An absorption profile centred at 78 megahertz in the sky-averaged spectrum

After stars formed in the early Universe, their ultraviolet light is expected, eventually, to have penetrated the primordial hydrogen gas and altered the excitation state of its 21-centimetre hyperfine line. This alteration would cause the gas to absorb photons from the cosmic microwave background, producing a spectral distortion that should be observable today at radio frequencies of less than 200 megahertz1. Here we report the detection of a flattened absorption profile in the sky-averaged radio spectrum, which is centred at a frequency of 78 megahertz and has a best-fitting full-width at half-maximum of 19 megahertz and an amplitude of 0.5 kelvin. The profile is largely consistent with expectations for the 21-centimetre signal induced by early stars; however, the best-fitting amplitude of the profile is more than a factor of two greater than the largest predictions2. This discrepancy suggests that either the primordial gas was much colder than expected or the background radiation temperature was hotter than expected. Astrophysical phenomena (such as radiation from stars and stellar remnants) are unlikely to account for this discrepancy; of the proposed extensions to the standard model of cosmology and particle physics, only cooling of the gas as a result of interactions between dark matter and baryons seems to explain the observed amplitude3. The low-frequency edge of the observed profile indicates that stars existed and had produced a background of Lyman-α photons by 180 million years after the Big Bang. The high-frequency edge indicates that the gas was heated to above the radiation temperature less than 100 million years later.

https://www.nature.com/articles/nature25792

And here’s the second related paper.

Possible interaction between baryons and dark-matter particles revealed by the first stars

The cosmic radio-frequency spectrum is expected to show a strong absorption signal corresponding to the 21-centimetre-wavelength transition of atomic hydrogen around redshift 20, which arises from Lyman-α radiation from some of the earliest stars1,2,3,4. By observing this 21-centimetre signal—either its sky-averaged spectrum5 or maps of its fluctuations, obtained using radio interferometers6,7—we can obtain information about cosmic dawn, the era when the first astrophysical sources of light were formed. The recent detection of the global 21-centimetre spectrum5 reveals a stronger absorption than the maximum predicted by existing models, at a confidence level of 3.8 standard deviations. Here we report that this absorption can be explained by the combination of radiation from the first stars and excess cooling of the cosmic gas induced by its interaction with dark matter8,9,10. Our analysis indicates that the spatial fluctuations of the 21-centimetre signal at cosmic dawn could be an order of magnitude larger than previously expected and that the dark-matter particle is no heavier than several proton masses, well below the commonly predicted mass of weakly interacting massive particles. Our analysis also confirms that dark matter is highly non-relativistic and at least moderately cold, and primordial velocities predicted by models of warm dark matter are potentially detectable. These results indicate that 21-centimetre cosmology can be used as a dark-matter probe.

https://www.nature.com/articles/nature25791
Post by: Star One on 02/28/2018 08:07 PM
The moon formed inside a vaporized Earth synestia

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A new explanation for the Moon's origin has it forming inside the Earth when our planet was a seething, spinning cloud of vaporized rock, called a synestia. The new model led by researchers at the University of California, Davis and Harvard University resolves several problems in lunar formation and is published Feb. 28 in the Journal of Geophysical Research - Planets.

Post by: Star One on 02/28/2018 08:51 PM
A Potentially Game-Changing Message from the Dawn of Time

https://blogs.scientificamerican.com/observations/a-potentially-game-changing-message-from-the-dawn-of-time/ (https://blogs.scientificamerican.com/observations/a-potentially-game-changing-message-from-the-dawn-of-time/)

More here.

Did Dark Matter Make The Early Universe Chill Out?

https://www.npr.org/sections/thetwo-way/2018/02/28/588833582/did-dark-matter-make-the-early-universe-chill-out
Post by: catdlr on 03/01/2018 08:53 AM
Want to See Space? Why Not Use One of NASA's Telescopes From the Comfort of Your Own Home

article: https://www.yahoo.com/news/want-see-space-why-not-155751923.html

Site: http://mo-www.harvard.edu/cgi-bin/OWN/Own.pl

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Each of the telescopes can be operated remotely and do not require a human operator. They are capable of viewing the moon, the Orion Nebula or nearby planets and are even powerful enough to snap a picture of other galaxies.
Post by: Star One on 03/02/2018 08:37 PM
HUBBLE OBSERVES EXOPLANET ATMOSPHERE IN MORE DETAIL THAN EVER BEFORE [HEIC1804]

01 March 2018
An international team of scientists has used the NASA/ESA Hubble Space Telescope to study the atmosphere of the hot exoplanet WASP-39b. By combining this new data with older data they created the most complete study yet of an exoplanet atmosphere. The atmospheric composition of WASP-39b hints that the formation processes of exoplanets can be very different from those of our own Solar System giants.

Investigating exoplanet atmospheres can provide new insight into how and where planets form around a star. "We need to look outward to help us understand our own Solar System," explains lead investigator Hannah Wakeford from the University of Exeter in the UK and the Space Telescope Science Institute in the USA.
Therefore the British-American team combined the capabilities of the NASA/ESA Hubble Space Telescope with those of other ground- and space-based telescopes for a detailed study of the exoplanet WASP-39b. They have produced the most complete spectrum of an exoplanet's atmosphere possible with present-day technology [1].
WASP-39b is orbiting a Sun-like star, about 700 light-years from Earth. The exoplanet is classified as a "Hot-Saturn", reflecting both its mass being similar to the planet Saturn in our own Solar System and its proximity to its parent star. This study found that the two planets, despite having a similar mass, are profoundly different in many ways. Not only is WASP-39b not known to have a ring system, it also has a puffy atmosphere that is free of high-altitude clouds. This characteristic allowed Hubble to peer deep into its atmosphere.
By dissecting starlight filtering through the planet's atmosphere [2] the team found clear evidence for atmospheric water vapour. In fact, WASP-39b has three times as much water as Saturn does. Although the researchers had predicted they would see water vapour, they were surprised by the amount that they found. This surprise, combined with the water abundance allowed to infer the presence of large amount of heavier elements in the atmosphere. This in turn suggests that the planet was bombarded by a lot of icy material which gathered in its atmosphere. This kind of bombardment would only be possible if WASP-39b formed much further away from its host star than it is right now.
"WASP-39b shows exoplanets are full of surprises and can have very different compositions than those of our Solar System," says co-author David Sing from the University of Exeter, UK.
The analysis of the atmospheric composition and the current position of the planet indicate that WASP-39b most likely underwent an interesting inward migration, making an epic journey across its planetary system. "Exoplanets are showing us that planet formation is more complicated and more confusing than we thought it was. And that's fantastic!", adds Wakeford.
Having made its incredible inward journey WASP-39b is now eight times closer to its parent star, WASP-39, than Mercury is to the Sun and it takes only four days to complete an orbit. The planet is also tidally locked, meaning it always shows the same side to its star. Wakeford and her team measured the temperature of WASP-39b to be a scorching 750 degrees Celsius. Although only one side of the planet faces its parent star, powerful winds transport heat from the bright side around the planet, keeping the dark side almost as hot.
"Hopefully this diversity we see in exoplanets will help us figure out all the different ways a planet can form and evolve," explains David Sing.
Looking ahead, the team wants to use the NASA/ESA/CSA James Webb Space Telescope – scheduled to launch in 2019 – to capture an even more complete spectrum of the atmosphere of WASP-39b. James Webb will be able to collect data about the planet's atmospheric carbon, which absorbs light of longer wavelengths than Hubble can see [3]. Wakeford concludes: "By calculating the amount of carbon and oxygen in the atmosphere, we can learn even more about where and how this planet formed."
NOTES
[1] Data used to produce the full spectrum was also collected by NASA's Spitzer Space Telescope and ESO's Very Large Telescope. In addition older data from Hubble were used.
[2] When starlight passes through the atmosphere of an exoplanet, it interacts with the atoms and molecules in it. This leaves a weak fingerprint of the atmosphere in the spectrum of the star. Certain peaks and troughs in the resulting spectrum correspond to specific atoms and molecules, allowing scientists to see exactly what gases make up the atmosphere.
[3] Given the large amount of heavy elements in WASP-39b's atmosphere, Wakeford and her team predict that carbon dioxide will be the dominant form of carbon. This could be measured at a wavelength of 4.5 micrometres with James Webb's NIRSpec instrument. Such follow-up investigations would allow further constraints to be placed on the ratio of carbon to oxygen, and on the metallicity of WASP-39b's atmosphere.
The Hubble Space Telescope is a project of international cooperation between ESA and NASA.

http://sci.esa.int/hubble/60022-hubble-observes-exoplanet-atmosphere-in-more-detail-than-ever-before-heic1804/
Post by: Star One on 03/02/2018 08:44 PM
A Stellar System with Three Super Earths
Friday, March 2, 2018
Science Update - A look at CfA discoveries from recent journals
Over 3500 extra-solar planets have been confirmed to date. Most of them were discovered using the transit method, and astronomers can combine the transit light curves with velocity wobble observations to determine the planet's mass and radius, and thereby constrain its interior structure. The atmosphere can also be studied in a transit by using the fact that the chemical composition of the atmosphere means its opacity varies with wavelength. By measuring the depth of the transit at different wavelengths, it is possible to infer the composition and temperature of the planet's atmosphere.

CfA astronomers Joseph Rodriguez, Andrew Vanderburg, Jason Eastman, David Latham, and Samuel Quinn and their team of scientists discovered three small transiting planets orbiting the star GJ9827 which lies at the relatively close distance of 100 light-years. The three exoplanets have radii of about 1.6, 1.3, and 2.1 Earth-radii respectively. All of them are categorized as super-Earths, that is, with masses that are larger than Earth’s but less than Neptune's. (Radial velocity measurements of the exoplanets, not included in this paper, have just been separately published and confirm this conclusion.)

GJ9827 is one of the few known stars to have multiple transiting terrestrial-sized exoplanets that are suited for atmospheric characterization. In fact, its three exoplanets are particularly interesting because two of them have radii between 1.5 and 2.0 Earth-radii. Across this range in radii, the composition of planets is expected to change from rocky to gaseous; moreover, there are relatively few such candidates for study. These planets orbit very close to the star, with periods of 1.2, 3.6 and 6.2 days respectively, and at these close distances they have fairly hot temperatures, estimated at 1172, 811 and 680 degrees kelvin. Future observations will probe their atmospheres and provide a much more detailed picture of this unusual family of super-Earths.

Reference(s):
"A System of Three Super Earths Transiting the Late K-Dwarf GJ 9827 at 30 pc," Joseph E. Rodriguez, Andrew Vanderburg, Jason D. Eastman, Andrew W. Mann, Ian J. M. Crossfield, David R. Ciardi, David W. Latham, and Samuel N. Quinn, AJ 155, 72, 2018.

https://www.cfa.harvard.edu/news/su201809
Post by: CuddlyRocket on 03/03/2018 10:02 PM
Yeah, I mentioned this paper on 8 February (Reply #333) with a link to the paper on arXiv (not a criticism, it's nearly a month ago and its difficult to remember everything!). Here's the link again: Magellan/PFS Radial Velocities of GJ 9827, a late K dwarf at 30 pc with Three Transiting Super-Earths (https://arxiv.org/abs/1711.01359)

It seems that this 'radii gap' (sometimes referred to as the Fulton gap) is becoming more firmly established!
Post by: Star One on 03/05/2018 07:36 PM
DONOR STAR BREATHES LIFE INTO ZOMBIE COMPANION

ESA's INTEGRAL space observatory has witnessed a rare event: the moment that winds emitted by a swollen red giant star revived its slow-spinning companion, the core of a dead star, bringing it back to life in a flash of X-rays.

The X-ray flare was first detected by INTEGRAL on 13 August 2017 from an unknown source in the direction of the crowded centre of our Milky Way. The sudden detection triggered a slew of follow-up observations in the following weeks to pin down the culprit.
The observations revealed a strongly magnetised and slowly rotating neutron star that had likely just begun to feed on material from a neighbouring red giant star.
Stars the mass of our Sun, and up to eight times more massive, evolve into red giants towards the end of their lives. Their outer layers puff up and expand millions of kilometres, their dusty, gassy shells blown away from the central star in relatively slow winds up to few hundreds of km/s.
Even larger stars, up to 25–30 times more massive than the Sun, race through their fuel and explode in a supernova, sometimes leaving behind a spinning stellar corpse with a strong magnetic field, known as a neutron star. This tiny core packs the mass of nearly one and half Suns into a sphere only 10 km across, making them some of the densest celestial objects known.

It is not uncommon to find stars paired together, but the new system of a neutron star and red giant is a particularly rare breed known as a 'symbiotic X-ray binary', with no more than 10 known.
"INTEGRAL caught a unique moment in the birth of a rare binary system," says Enrico Bozzo from University of Geneva and lead author of the paper that describes the discovery. "The red giant released a sufficiently dense slow wind to feed its neutron star companion, giving rise to high-energy emission from the dead stellar core for the first time."
The pairing is certainly peculiar. ESA's XMM-Newton and NASA's NuSTAR space telescopes showed that the neutron star spins almost every two hours – very slow compared with other neutron stars, which can spin up to many times per second. Then, the first measurement of the magnetic field of such a neutron star revealed it to be surprisingly strong.
A strong magnetic field typically points to a young neutron star – the magnetic field is thought to fade over time – while a red giant is much older, making it a bizarre couple to have grown up together.
"These objects are puzzling," says Enrico. "It might be that either the neutron star magnetic field does not decay substantially with time after all, or the neutron star actually formed later in the history of the binary system. That would mean it collapsed from a white dwarf into a neutron star as a result of feeding off the red giant over a long time, rather than becoming a neutron star as a result of a more traditional supernova explosion of a short-lived massive star."
With a young neutron star and an old red giant, at some point the winds travelling from the puffed-up giant will begin to rain on to the smaller star, slowing its spin and emitting X-rays.
"We haven't seen this object before in the past 15 years of our observations with INTEGRAL, so we believe we saw the X-rays turning on for the first time," says Erik Kuulkers, ESA's INTEGRAL project scientist. "We'll continue to watch how it behaves in case it is just a long 'burp' of winds, but so far we haven't seen any significant changes."
NOTES FOR EDITORS
"IGR J17329-2731: The birth of a symbiotic X-ray binary," by E. Bozzo et al. is accepted for publication in Astronomy & Astrophysics.
The rapid response of the follow-up observations was enabled by the SmartNet community. This included important contributions from ESA's XMM-Newton and NASA’s NuSTARand Swift space telescopes, and the ground-based Southern Astrophysical Research Telescope, Faulkes Telescopes North and South and the Las Cumbres Observatory.

http://sci.esa.int/integral/60029-donor-star-breathes-life-into-zombie-companion/
Post by: CuddlyRocket on 03/06/2018 01:35 AM
Konstantin Batygin has a new paper out. Here's the Caltech release:

Massive Astrophysical Objects Governed by Subatomic Equation
The Schrödinger Equation makes an unlikely appearance at the astronomical scale (http://www.caltech.edu/news/massive-astrophysical-objects-governed-subatomic-equation-81517)

The paper itself can be found here (pdf):

Schrodinger evolution of self-gravitating discs (https://authors.library.caltech.edu/85094/1/sty162.pdf)

Quote
(Abstract)
An understanding of the long-term evolution of self-gravitating discs ranks among the classic outstanding problems of astrophysics. In this work, we show that the secular inclination dynamics of a geometrically thin quasi-Keplerian disc, with a surface density profile that scales as the inverse square-root of the orbital radius, are described by the time-dependent Schrodinger equation. Within the context of this formalism, nodal bending waves correspond to the eigenmodes of a quasi-particle’s wavefunction, confined in an infinite square well with boundaries given by the radial extent of the disc. We further show that external secular perturbations upon self-gravitating discs exhibit a mathematical similarity to quantum scattering theory. Employing this framework, we derive an analytic criterion for the gravitational rigidity of a nearly-Keplerian disc under external perturbations. Applications of the theory to circumstellar discs and Galactic nuclei are discussed.

As you might expect from one of Konstantin's papers, it's a bit mathematical!
Post by: Star One on 03/07/2018 08:37 AM
Massive Astrophysical Objects Governed by Subatomic Equation

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The Schrödinger Equation makes an unlikely appearance at the astronomical scale

Quantum mechanics is the branch of physics governing the sometimes-strange behavior of the tiny particles that make up our universe. Equations describing the quantum world are generally confined to the subatomic realm—the mathematics relevant at very small scales is not relevant at larger scales, and vice versa. However, a surprising new discovery from a Caltech researcher suggests that the Schrödinger Equation—the fundamental equation of quantum mechanics—is remarkably useful in describing the long-term evolution of certain astronomical structures.

http://m.caltech.edu/news/massive-astrophysical-objects-governed-subatomic-equation-81517
Post by: Star One on 03/07/2018 07:24 PM
eso1809 — Photo Release

ALMA Reveals Inner Web of Stellar Nursery

New data from the Atacama Large Millimeter/submillimeter Array (ALMA) and other telescopes have been used to create this stunning image showing a web of filaments in the Orion Nebula. These features appear red-hot and fiery in this dramatic picture, but in reality are so cold that astronomers must use telescopes like ALMA to observe them.

This spectacular and unusual image shows part of the famous Orion Nebula, a star formation region lying about 1350 light-years from Earth. It combines a mosaic of millimetre-wavelength images from the Atacama Large Millimeter/submillimeter Array (ALMA) and the IRAM 30-metre telescope, shown in red, with a more familiar infrared view from the HAWK-I instrument on ESO’s Very Large Telescope, shown in blue. The group of bright blue-white stars at the upper-left is the Trapezium Cluster — made up of hot young stars that are only a few million years old.

The wispy, fibre-like structures seen in this large image are long filaments of cold gas, only visible to telescopes working in the millimetre wavelength range. They are invisible at both optical and infrared wavelengths, making ALMA one of the only instruments available for astronomers to study them. This gas gives rise to newborn stars — it gradually collapses under the force of its own gravity until it is sufficiently compressed to form a protostar — the precursor to a star.

The scientists who gathered the data from which this image was created were studying these filaments to learn more about their structure and make-up. They used ALMA to look for signatures of diazenylium gas, which makes up part of these structures. Through doing this study, the team managed to identify a network of 55 filaments.

The Orion Nebula is the nearest region of massive star formation to Earth, and is therefore studied in great detail by astronomers seeking to better understand how stars form and evolve in their first few million years. ESO’s telescopes have observed this interesting region multiple times, and you can learn more about previous discoveries here, here, and here.

This image combines a total of 296 separate individual datasets from the ALMA and IRAM telescopes, making it one of the largest high-resolution mosaics of a star formation region produced so far at millimetre wavelengths [1].

Notes
[1] Earlier mosaics of Orion at millimetre wavelengths had used single-dish telescopes, such as APEX. The new observations from ALMA and IRAM use interferometry to combine the signals from multiple, widely-separated antennas to create images showing much finer detail.

http://www.eso.org/public/news/eso1809/
Post by: Star One on 03/08/2018 11:07 AM
Enceladus and the Conditions for Life

Post by: Star One on 03/08/2018 08:22 PM
A PECULIAR GALACTIC CLASH [HEIC1805]

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Galaxies are not static islands of stars – they are dynamic and ever-changing, constantly on the move through the darkness of the Universe. Sometimes, as seen in this spectacular Hubble image of Arp 256, galaxies can collide in a crash of cosmic proportions.

http://sci.esa.int/hubble/60037-a-peculiar-galactic-clash-heic1805/
Post by: Star One on 03/09/2018 07:20 PM
The HR 4796A Debris System: Discovery of Extensive Exo-ring Dust Material

The optically and IR-bright and starlight-scattering HR 4796A ringlike debris disk is one of the most- (and best-) studied exoplanetary debris systems. The presence of a yet-undetected planet has been inferred (or suggested) from the narrow width and inner/outer truncation radii of its r = 1farcs05 (77 au) debris ring. We present new, highly sensitive Hubble Space Telescope (HST) visible-light images of the HR 4796A circumstellar debris system and its environment over a very wide range of stellocentric angles from 0farcs32 (23 au) to ≈15'' (1100 au). These very high-contrast images were obtained with the Space Telescope Imaging Spectrograph (STIS) using six-roll PSF template–subtracted coronagraphy suppressing the primary light of HR 4796A, with three image-plane occulters, and simultaneously subtracting the background light from its close angular proximity M2.5V companion. The resulting images unambiguously reveal the debris ring embedded within a much larger, morphologically complex, and biaxially asymmetric exo-ring scattering structure. These images at visible wavelengths are sensitive to and map the spatial distribution, brightness, and radial surface density of micron-size particles over 5 dex in surface brightness. These particles in the exo-ring environment may be unbound from the system and interacting with the local ISM. Herein, we present a new morphological and photometric view of the larger-than-prior-seen HR 4796A exoplanetary debris system with sensitivity to small particles at stellocentric distances an order of magnitude greater than has previously been observed.

http://iopscience.iop.org/article/10.3847/1538-3881/aaa3f3/pdf
Post by: Star One on 03/09/2018 07:42 PM
3 NASA Satellites Recreate Solar Eruption in 3-D

The more solar observatories, the merrier: Scientists have developed new models to see how shocks associated with coronal mass ejections, or CMEs, propagate from the Sun — an effort made possible only by combining data from three NASA satellites to produce a much more robust mapping of a CME than any one could do alone.

Much the way ships form bow waves as they move through water, CMEs set off interplanetary shocks when they erupt from the Sun at extreme speeds, propelling a wave of high-energy particles. These particles can spark space weather events around Earth, endangering spacecraft and astronauts.

Understanding a shock’s structure — particularly how it develops and accelerates — is key to predicting how it might disrupt near-Earth space. But without a vast array of sensors scattered through space, these things are impossible to measure directly. Instead, scientists rely upon models that use satellite observations of the CME to simulate the ensuing shock’s behavior.

Using data from three different satellites, scientists have developed new models that recreate, in 3-D, CMEs and shocks, separately. This movie illustrates the recreation of a CME and shock that erupted from the Sun on March 7, 2011. The pink lines show the CME structure and the yellow lines show the structure of the shock - a side effect of the CME that can spark space weather events around Earth.
Credits: NASA’s Goddard Space Flight Center/GMU/APL/Joy Ng
Download this video in HD formats from NASA Goddard's Scientific Visualization Studio

The scientists — Ryun-Young Kwon, a solar physicist at George Mason University in Fairfax, Virginia, and Johns Hopkins University Applied Physics Laboratory, or APL, in Laurel, Maryland, and APL astrophysicist Angelos Vourlidas — pulled observations of two different eruptions from three spacecraft: ESA/NASA’s Solar and Heliospheric Observatory, or SOHO, and NASA’s twin Solar Terrestrial Relations Observatory, or STEREO, satellites. One CME erupted in March 2011 and the second, in February 2014.

The scientists fit the CME data to their models — one called the “croissant” model for the shape of nascent shocks, and the other the “ellipsoid” model for the shape of expanding shocks — to uncover the 3-D structure and trajectory of each CME and shock.

Each spacecraft’s observations alone weren’t sufficient to model the shocks. But with three sets of eyes on the eruption, each of them spaced nearly evenly around the Sun, the scientists could use their models to recreate a 3-D view. Their work confirmed long-held theoretical predictions of a strong shock near the CME nose and a weaker shock at the sides.

In time, shocks travel away from the Sun, and thanks to the 3-D information, the scientists could reconstruct their journey through space. The modeling helps scientists deduce important pieces of information for space weather forecasting — in this case, for the first time, the density of the plasma around the shock, in addition to the speed and strength of the energized particles. All of these factors are key to assessing the danger CMEs present to astronauts and spacecraft. Their results are summarized in a paper published in the Journal of Space Weather and Space Climate published on Feb. 13, 2018.
Post by: Star One on 03/13/2018 08:25 PM
VOLCANIC WORMHOLE

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The organic and intricate features of a volcanic cave come alive in great detail in this three-dimensional image of La Cueva de Los Verdes in Lanzarote, Spain. Some of the most innovative scanning technologies have produced the largest 3D scan of a lava tube on Earth.

Lava tubes are planetary caves. Similar cave systems have been found from orbit on the Moon and Mars. These underground formations could one day provide safe habitats for humans on other celestial bodies – they provide constant temperature and a good shelter against cosmic radiation and micrometeorites.

Understanding the origins and formation of these caves on Earth is a passage for simulating the future of planetary explorers across the Solar System.

A team of speleologists from the University of Padova, Italy mapped the main path of the cave system aided by ESA astronaut Matthias Mauer. The image covers a 1.3 km section of the lava tube with an unprecedented resolution of few centimetres.

http://m.esa.int/spaceinimages/Images/2018/03/Volcanic_wormhole
Post by: Star One on 03/15/2018 05:56 AM
We Just Caught The Strongest-Ever Fast Radio Burst, But They're Still Super Mysterious

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Three more of the mysterious fast radio burst (FRB) signals have been detected this month, and one of them is a real record-breaker, coming in with the highest signal-to-noise ratio ever recorded. That makes it the "brightest" FRB that's ever been observed.

The signals came in on March 1, March 9 (that's the really bright one) and March 11, snagged by the Parkes Observatory radio telescope in remote Australia.

They are called FRB 180301, FRB 180309 and FRB 180311, following the fast radio burst convention of being named for the dates on which they occurred.

Post by: Star One on 03/15/2018 07:55 PM
New instrument built to search for Earth-like exo-planets

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Yale University astronomers have developed a powerful new spectrometer to search for Earth-size planets around nearby stars. Expected to improve precision over earlier ground-based instruments by a factor of 10, the Extreme Precision Spectrometer – EXPRES – is now in operation at the Lowell Observatory’s Discovery Channel Telescope in Arizona.

https://astronomynow.com/2018/03/14/new-instrument-built-to-search-for-earth-like-exo-planets/
Post by: Star One on 03/15/2018 08:12 PM
Mystery of Purple Lights in Sky Solved With Help From Citizen Scientists

https://www.nasa.gov/feature/goddard/2018/mystery-of-purple-lights-in-sky-solved-with-help-from-citizen-scientists
Post by: Star One on 03/18/2018 08:27 PM
Thought the astronomers on here might appreciate the sentiments expressed on this Twitter thread.

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This thread might be interesting if you’ve ever wondered: “Could the govt be hiding knowledge of a killer asteroid from us?” Answer is no: we’d all be talking about it on Twitter. (Thread is about worrisome object that, with more data, turned out NOT to be a threat.)
Post by: Star One on 03/18/2018 08:32 PM
Didn’t want to start a new thread yet for this news.

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NASA has changed its mind and will allow proposals for its next Discovery competition to use RTGs, according to an email sent late yesterday:
Post by: redliox on 03/19/2018 01:58 AM
Didn’t want to start a new thread yet for this news.

Quote
NASA has changed its mind and will allow proposals for its next Discovery competition to use RTGs, according to an email sent late yesterday:

Good news although it'd probably fit better into the Discovery or New Frontiers threads.
Post by: Star One on 03/19/2018 07:32 PM
A Changing Landscape at Ceres

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Ceres turns out to be a livelier place than we might have imagined. Continuing analysis of data from the Dawn spacecraft is showing us an object where surface changes evidently caused by temperature variations induced by the dwarf planet’s orbit are readily visible even in short time frames. Two new papers on the Dawn data are now out in Science Advances, suggesting variations in the amount of surface ice as well as newly exposed crustal material.

https://www.centauri-dreams.org/2018/03/19/a-changing-landscape-at-ceres/
Post by: Star One on 03/20/2018 08:32 PM
Measuring White Dwarf Masses with Gravitational Lensing

Friday, March 16, 2018

Science Update - A look at CfA discoveries from recent journals

Measuring the mass of a celestial body is one of the most challenging tasks in observational astronomy. The most successful method uses binary systems because the orbital parameters of the system depend on the two masses. In the case of black holes, neutron stars, and white dwarfs, the end states of stellar evolution, many are isolated objects, and most of them are also very faint. As a result, astronomers still do not know the distribution of their masses. They are of great interest, however, because they participate in dramatic events like the accretion of material and emission of energetic radiation, or in mergers that can result in gravitational waves, gamma-ray bursts, or Type Ia supernovae, all of which depend on an object's mass.

CfA astronomers Alexander Harding, Rosanne Di Stefano, and Claire Baker and three colleagues propose a new method for determining the masses of isolated compact objects: gravitational lensing. The path of a light beam will be bent by the presence of mass, an effect calculated by General Relativity. A massive body will act like a lens to distort the image of an object seen behind it when the two are close to being aligned along our line-of-sight, and the specifics of the image distortions will depend on the body's mass. The astronomers describe the prospects for predicting lensing events generated by nearby compact objects as their motions take them across the field of background stars.

The team estimates that the nearby population of compact objects contains about 250 neutron stars, 5 black holes, and about 35,000 white dwarf stars suitable for this study. Knowing the general motions of the white dwarfs across the sky, they obtain a statistical estimate of about 30-50 lensing events per decade that could be spotted by Hubble, ESA's Gaia mission, or NASA's new JWST telescope. The next step in this effort is to use ongoing stellar surveys like that of Gaia to refine the bodies' positions and motions to be able to predict specifically which objects to monitor for lensing.

Reference(s):
"Predicting Gravitational Lensing by Stellar Remnants," Alexander J. Harding, R. Di Stefano, S. Lepine, J. Urama, D. Pham and C. Baker, MNRAS 475, 79, 2018.

https://www.cfa.harvard.edu/news/su201811
Post by: Star One on 03/21/2018 08:09 PM
K2-231 b: A sub-Neptune exoplanet transiting a solar twin in Ruprecht 147

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We identify a sub-Neptune exoplanet (Rp=2.5±0.2 R⊕) transiting a solar twin in the Ruprecht 147 star cluster (3 Gyr, 300 pc, [Fe/H] = +0.1 dex). The ~81 day light curve for EPIC 219800881 (V = 12.71) from K2 Campaign 7 shows six transits with a period of 13.84 days, a depth of ~0.06%, and a duration of ~4 hours. Based on our analysis of high-resolution MIKE spectra, broadband optical and NIR photometry, the cluster parallax and interstellar reddening, and isochrone models from PARSEC, Dartmouth, and MIST, we estimate the following properties for the host star: M⋆=1.01±0.03 M⊙, R⋆=0.95±0.03 R⊙, and Teff=5695±50 K. This star appears to be single, based on our modeling of the photometry, the low radial velocity variability measured over nearly ten years, and Keck/NIRC2 adaptive optics imaging and aperture-masking interferometry. Applying a probabilistic mass-radius relation, we estimate that the mass of this planet is Mp=7+5−3 M⊕, which would cause a RV semi-amplitude of K=2±1 m s−1 that may be measurable with existing precise RV facilities. After statistically validating this planet with BLENDER, we now designate it K2-231 b, making it the second sub-stellar object to be discovered in Ruprecht 147 and the first planet; it joins the small but growing ranks of 23 other planets found in open clusters.

https://arxiv.org/abs/1803.07430
Post by: Star One on 03/21/2018 08:28 PM
Evidence that a star disturbed prehistory solar system comets

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About 70,000 years ago, during human occupation of the planet, a small, reddish star approached our solar system and gravitationally disturbed comets and asteroids. Astronomers from the Complutense University of Madrid and the University of Cambridge have verified that the movement of some of these objects is still marked by that stellar encounter.

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Now, two astronomers from the Complutense University of Madrid, the brothers Carlos and Raúl de la Fuente Marcos, together with the researcher Sverre J. Aarseth of the University of Cambridge (United Kingdom), have analyzed for the first time nearly 340 solar system objects with hyperbolic orbits (very open V-shaped, rather than elliptical) They have concluded that the trajectories of some of these were influenced by the passage of Scholz's star.

"Using numerical simulations, we have calculated the radiants or positions in the sky from which all these hyperbolic objects seem to come," explains Carlos de la Fuente Marcos, a co-author of the study now published in Monthly Notices of the Royal Astronomical Society.

"In principle," he adds, "one would expect those positions to be evenly distributed in the sky, particularly if these objects come from the Oort cloud. However, what we find is very different—a statistically significant accumulation of radiants. The pronounced over-density appears projected in the direction of the constellation of Gemini, which fits the close encounter with Scholz's star."

I love this thought of seeing another red star so bright in the sky.

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Scholz's star is actually a binary system formed by a small red dwarf with about 9 percent of the mass of the sun, around which a much less bright and smaller brown dwarf orbits. It is likely that human ancestors saw its faint reddish light during prehistorical nights.

https://phys.org/news/2018-03-evidence-star-disturbed-prehistory-solar.amp

Post by: as58 on 03/21/2018 09:22 PM
Quote
Scholz's star is actually a binary system formed by a small red dwarf with about 9 percent of the mass of the sun, around which a much less bright and smaller brown dwarf orbits. It is likely that human ancestors saw its faint reddish light during prehistorical nights.

https://phys.org/news/2018-03-evidence-star-disturbed-prehistory-solar.amp

Only if human ancestors had much more sensitive eyes than we do. Even at its closest approach the star would have been fainter than 10th magnitude.
Post by: CuddlyRocket on 03/22/2018 05:28 AM
Evidence that a star disturbed prehistory solar system comets

Here's the paper on arXiv:

Where the Solar system meets the solar neighbourhood: patterns in the distribution of radiants of observed hyperbolic minor bodies (https://arxiv.org/pdf/1802.00778.pdf)
Post by: Star One on 03/22/2018 06:51 AM
Quote
Scholz's star is actually a binary system formed by a small red dwarf with about 9 percent of the mass of the sun, around which a much less bright and smaller brown dwarf orbits. It is likely that human ancestors saw its faint reddish light during prehistorical nights.

https://phys.org/news/2018-03-evidence-star-disturbed-prehistory-solar.amp

Only if human ancestors had much more sensitive eyes than we do. Even at its closest approach the star would have been fainter than 10th magnitude.

All the articles I’ve seen about this have reported the same thing so I assume it had come from an official press release somewhere?

Especially odd as I’ve looked into this and you’re completely correct, it’s apparent magnitude would have been 11.4 - too faint to be seen with the naked eye.
Post by: jebbo on 03/22/2018 07:05 AM
All the articles I’ve seen about this have reported the same thing so I assume it had come from an official press release somewhere?

I think it comes from the final line of the release from the Spanish Foundation for Science & Technology:

Quote
Scholz's star is actually a binary system formed by a small red dwarf with about 9 percent of the mass of the sun, around which a much less bright and smaller brown dwarf orbits. It is likely that human ancestors saw its faint reddish light during prehistorical nights.

Article here (https://phys.org/news/2018-03-evidence-star-disturbed-prehistory-solar.html)

It's well worth reading Eric Mamajek's FAQ for the initial discovery in 2015: here (http://www.pas.rochester.edu/~emamajek/flyby.html)

--- Tony
Post by: Bynaus on 03/22/2018 11:49 AM
As I read this, the only thing that might have been visible are the (potential) occasional flares.
Post by: Star One on 03/22/2018 07:56 PM
As I read this, the only thing that might have been visible are the (potential) occasional flares.

Here’s some more thoughts on this topic

Quote
Scholz’s Star is a binary system, a red dwarf orbited by a brown dwarf, and it is likely that there was a time when our ancestors could see it in the sky. But only barely — Eric Mamajek has pointed out that even at its closest approach, the apparent magnitude would have been in the range of 11.4, which is five magnitudes fainter than what the naked eye can see, even in the pristine skies of paleolithic Earth. What might have been visible would have been flares from the M-dwarf, which could have created short-lived transient events, fleeting but noticeable.

https://www.centauri-dreams.org/2018/03/22/a-prehistoric-close-pass/
Post by: CuddlyRocket on 03/23/2018 07:02 PM
It is likely that human ancestors saw its faint reddish light during prehistorical nights.

Technically correct, but misleading. And in a press release too - who would'a thunk it? :)
Post by: Star One on 03/23/2018 07:33 PM
Hubble Solves Cosmic 'Whodunit' with Interstellar Forensics

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Winner Declared in Tug-of-War Between Two Satellite Galaxies of the Milky Way

In a cosmic tug-of-war between two dwarf galaxies orbiting the Milky Way, only NASA’s Hubble Space Telescope can see who’s winning. The players are the Large and Small Magellanic Clouds, and as they gravitationally tug at each other, one of them has pulled out a huge amount of gas from its companion. This shredded and fragmented gas, called the Leading Arm, is being devoured by the Milky Way and feeding new star birth in our galaxy. But which dwarf galaxy is doing the pulling, and whose gas is now being feasted upon? Scientists used Hubble’s ultraviolet vision to chemically analyze the gas in the Leading Arm and determine its origin. After years of debate, we now have the answer to this “whodunit” mystery.

http://hubblesite.org/news_release/news/2018-15

Post by: Star One on 03/26/2018 07:32 PM
Kepler Solves Mystery of Fast and Furious Explosions

Space Observatory Captures the Details of an Unusual Stellar Detonation

The universe is so huge that it's estimated that a star explodes as a supernova once every second. Astronomers capture a small fraction of these detonations because they are comparatively short-lived, like fireflies flickering on a summer evening. After skyrocketing to a sudden peak in brightness, a supernova can take weeks to slowly fade away.

For the past decade astronomers have been befuddled by a more curious "flash-in-the-pan" that pops up and then disappears in just a few days, not weeks. It's called a Fast-Evolving Luminous Transient (FELT). Only a few FELTs have been seen in telescopic sky surveys because they are so brief.

Then along came NASA's Kepler Space Telescope that caught a FELT in the act. Kepler's outstanding ability to precisely record changes in the brightness of celestial objects was designed to look for planets across our galaxy. But a great spinoff from the observatory is to go supernova hunting too.

Kelper's unique capabilities captured the properties of the blast. This allowed astronomers to exclude a range of theories about how FELTs happen, and converge on a plausible model. They conclude that the brief flash is from a vast shell of material around a supernova that abruptly lights up when the supernova blast wave crashes into it.

Release ID: STScI-2018-18

http://hubblesite.org/news_release/news/2018-18
Post by: Star One on 03/28/2018 07:24 AM
U2 Spy Plane Flies Through a Dazzling Aurora

https://video.nationalgeographic.com/video/news/180327-air-force-pilot-flies-into-aurora-vin-spd (https://video.nationalgeographic.com/video/news/180327-air-force-pilot-flies-into-aurora-vin-spd)
Post by: Star One on 03/28/2018 08:06 PM
Life beyond Earth: No plate tectonics, no problem

Scientists prepare to look in unexpected places for ‘exoplanet biosignatures’

HOUSTON — (March 28, 2018) — Scientists looking for life on distant planets are making plans to search non-Earth-like planets based on discoveries within our solar system that are challenging long-standing ideas about habitable zones, plate tectonics and more.

In a new paper published online this week, Rice University geophysicist Adrian Lenardic and more than a dozen co-authors outline a path for both finding potential life signs around other stars and determining how likely it is that those signs are caused by alien life. The paper, “Exoplanet Biosignatures: Future Directions,” is available online and due to be published in Astrobiology.

An artist's impression of Ross 128 b, a temperate, rocky planet about 11 light-years from EarthLong Description
An artist’s impression of Ross 128 b, a temperate, rocky planet about 11 light-years from Earth that could have the necessary conditions for maintaining liquid surface water. (Photo courtesy of European Southern Observatory/M. Kornmesser)
Lenardic, who specializes in studying planetary dynamics, also authored an associated paper, “Volcanic-Tectonic Modes and Planetary Life Potential,” that will be published as a chapter in the upcoming “Handbook of Exoplanets” from Springer Publishing.

“It used to be the thought that life could only exist in a narrow zone near a planet’s star because you need to be there to maintain liquid water,” said Lenardic, professor of Earth, environmental and planetary sciences. “Then, we send Voyager out to a moon of Jupiter and, lo and behold, it shows strong indications of a subsurface ocean. That’s because there is another energy source that did not get its proper due — tidal forces from the intense gravitational pull of Jupiter.

“This has opened up the range over our own solar system in which life can exist, and I think a lot of the gist of the forthcoming papers is that much of what we’re seeing is expanding the zone and expanding our thinking about the conditions needed for life. So, as we look for life around other stars, we should also expand our search strategies or we might miss something.”

Astronomers have cataloged more than 3,700 planets around distant stars. The 21-foot diameter mirror on the James Webb Space Telescope, which is set to launch in 2019, will be able to examine the atmospheres of rocky planets around distant stars, and astronomers are already designing future missions and instruments that will look for specific atmospheric signatures of life.

“A goal was to frame the problem,” Lenardic said of the new biosignature paper, which sprang from an exoplanet workshop that brought together a range of scientists. “The workshop team wanted to come up with a means of assigning a likelihood of life based on a given set of observations of a distant planet.”

Adrian Lenardic (Photo by Jeff Fitlow/Rice University)
He said the search for exolife is a team sport that involves biologists, astronomers, planetary scientists and others who collaborate through groups such as NASA’s Nexus for Exoplanet System Science (NExSS) project and the European Space Agency’s International Summer School in Astrobiology.

Lenardic’s contribution is to examine how the internal energy of planets, and associated volcanic-tectonic activity, influence their climate and ability to sustain life.

“When I teach planetary science, one question I actually give students is, ‘What is life? Give me a definition.’ And it’s not easy,” Lenardic said. He noted that students and working scientists have put forward a range of answers.

“But if we can agree on one thing, it’s that life needs energy,” he said. “We’ve thought about the sun as an energy source for a long time, and we’ve come to appreciate a planet’s internal energy, which comes from decay of radioactive elements within its rocky interior. Jupiter’s moons have taught us to also appreciate tidal forcing, and we’re starting to find exoplanets that have orbits that allow for significant tidal forcing.”

Lenardic said plate tectonics, much like the narrow habitable zone, is another long-held criterion for planetary habitability that is being challenged by recent findings.

Plate tectonics is the large-scale process that governs the movements of Earth’s crust.

“It is a particular surface manifestation of a planet’s internal energy, but it is not the only possible mode of volcanic and tectonic activity on a planet,” Lenardic said.

On Earth, plate tectonics plays a role in modulating climate, but the idea that plate tectonics is crucial for life is challenged by increasingly sophisticated models of planetary climates. For example, in a January study in the Journal of Geophysical Research, Lenardic and colleagues showed how water could be maintained on worlds without plate tectonics. The chapter in the upcoming “Handbook of Exoplanets” further explores this idea by considering planetary life potential under a range of tectonic modes that differ from Earth’s.

“I’m an optimist,” Lenardic said. “We’re at the first point in our history as humans where we might actually have some observations from other planets that we can use to test any of these ideas about life beyond our own. It can be easy to be Earth-centric and assume that life requires a planet like our own. But what we are seeing within our solar system is causing us to question this. One of the things I have learned from the history of exploring our own solar system is to be prepared for surprise. As we move beyond our solar system, in our search for life, that lesson is driving us to adapt our search strategies.”

Co-authors of the Astrobiology paper include lead author Sara Walker, Evgenya Shkolnik and Harrison Smith of Arizona State University; William Bains of the MIT; Leroy Cronin of the University of Glasgow; Shiladitya DasSarma of the University of Maryland School of Medicine; Sebastian Danielache of the Tokyo Institute of Technology and Sophia University in Tokyo; Shawn Domagal-Goldman of NASA’s Goddard Space Flight Center and the University of Washington’s Virtual Planetary Laboratory; Betul Kacar of Harvard, the University of Montana and the University of Arizona; Nancy Kiang of NASA’s Goddard Institute for Space Studies; Christopher Reinhard of the University of California, Riverside and Georgia Tech; William Moore of Hampton University and the National Institute of Aerospace in Hampton, Va.; and Edward Schwieterman of the Blue Marble Space Institute of Science in Seattle, the University of Washington’s Virtual Planetary Laboratory, the University of California, Riverside and the Universities Space Research Association in Columbia, Md.

-30-

https://www.eso.org/public/usa/images/eso1736a/
CAPTION: An artist’s impression of Ross 128 b, a temperate, rocky planet about 11 light-years from Earth that could have the necessary conditions for maintaining liquid surface water. (Photo courtesy of European Southern Observatory/M. Kornmesser)

http://news.rice.edu/files/2018/03/0323_EXOLIFE-al-lg2-1ax3yr7.jpg
CAPTION: Adrian Lenardic (Photo by Jeff Fitlow/Rice University)

The Astrobiology paper is available at: https://arxiv.org/ftp/arxiv/papers/1705/1705.08071.pdf

The planetary dynamics paper is available at: https://www.researchgate.net/publication/320456190_Volcanic-Tectonic_Modes_and_Planetary_Life_Potential

Post by: Star One on 03/28/2018 08:27 PM
Newly-discovered planet is hot, metallic and dense as Mercury

Hot, metallic, Earth-sized planet with a density similar to Mercury detected 339 light years away and characterised by global team of astronomers, including the University of Warwick
K2-229b is 20% larger than Earth but has a mass 2.6 times greater - and a dayside temperature of over 2000°C
Discovering details about far-flung planets across the universe gives us more clues as to how planets in our own solar system formed

https://warwick.ac.uk/newsandevents/pressreleases/newly-discovered_planet_is
Post by: missinglink on 03/28/2018 09:21 PM
Newly-discovered planet is hot, metallic and dense as Mercury
There be gold in them thar planets, GOLD! and it's mine, all mine! you can't have any of it.
Post by: Star One on 03/29/2018 06:36 AM
Dark matter 'missing' in a galaxy far, far away

Quote
Galaxies and dark matter go hand in hand; you typically don't find one without the other. So when researchers uncovered a galaxy, known as NGC1052-DF2, that is almost completely devoid of the stuff, they were shocked.

https://m.phys.org/news/2018-03-dark-galaxy.html
Post by: Star One on 03/29/2018 11:48 AM
RARE 'RUNAWAY' SUPERGIANT STAR DISCOVERED SPEEDING ACROSS NEIGHBORING GALAXY AT 300,000 MPH

http://www.newsweek.com/rare-runaway-supergiant-star-discovered-speeding-across-neighboring-galaxy-864578
Post by: leovinus on 03/29/2018 01:07 PM
Dark matter 'missing' in a galaxy far, far away

Quote
Galaxies and dark matter go hand in hand; you typically don't find one without the other. So when researchers uncovered a galaxy, known as NGC1052-DF2, that is almost completely devoid of the stuff, they were shocked.

https://m.phys.org/news/2018-03-dark-galaxy.html

A bit of context makes this even more interesting. Two years ago, the same author with the same instrument found a galaxy which was conjectured to consist of 99.9% dark matter https://www.space.com/33850-weird-galaxy-is-mostly-dark-matter.html (https://www.space.com/33850-weird-galaxy-is-mostly-dark-matter.html). In other words, we find galaxies with extreme mixing ratios <0..99.9> for matter and dark matter, and it seems more than just one example.
Post by: Star One on 04/03/2018 07:49 PM
Astronomers find 72 bright and fast explosions

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Gone in a (cosmological) flash: a team of astronomers found 72 very bright, but quick events in a recent survey and are still struggling to explain their origin. Miika Pursiainen of the University of Southampton will present the new results on Tuesday 3 April at the European Week of Astronomy and Space Science.

The scientists found the transients in data from the Dark Energy Survey Supernova Programme (DES-SN). This is part of a global effort to understand dark energy, a component driving an acceleration in the expansion of the Universe. DES-SN uses a large camera on a 4-metre telescope in the Cerro Tololo Inter-American Observatory (CTIO) in the Chilean Andes. The survey looks for supernovae, the explosion of massive stars at the end of their lives. A supernova explosion can briefly be as bright as a whole galaxy, made up of hundreds of billions of stars.

Is the Milky Way getting bigger?

Quote
The galaxy we inhabit, the Milky Way, may be getting even bigger, according to Cristina Martínez-Lombilla, a PhD candidate at the Instituto de Astrofísica de Canarias in Tenerife, Spain, and her collaborators. She will present the work of her team in a talk on Tuesday 3 April at the European Week of Astronomy and Space Science in Liverpool.

Gravitational waves created by black holes in the cenetr of most galaxies

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Gravitational waves may be forged in the heart of the galaxy, says a new study led by PhD student Joseph Fernandez at Liverpool John Moores University. He sets out the work in a presentation on 3rd April at the European Week of Astronomy and Space Science in Liverpool.

https://www.sciencedaily.com/releases/2018/04/180402192817.htm

Post by: Star One on 04/04/2018 08:31 PM
Rare metals on Mars and Earth implicate colossal impacts

Quote
New research has revealed that a giant impact on Mars more than four billion years ago would explain the unusual amount of “iron loving” elements in the Red Planet.

https://astronomynow.com/2018/04/04/rare-metals-on-mars-and-earth-implicate-colossal-impacts/

Deep inside Perseus A – A telescope larger than the Earth makes a sharp image of the formation of black hole jets in the core of a radio galaxy

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Researchers have imaged newly forming jets of plasma from a massive black hole with unprecedented accuracy. Radio images made with a combination of telescopes in space and on the ground resolve the jet structure merely a couple of hundred black hole radii or 12 light days from its launching site.

https://www.sciencedaily.com/releases/2018/04/180403090046.htm

New findings from NYU Abu Dhabi and JPL about how 'giant' planets impact neighbors' habitability

Quote
Abu Dhabi, UAE (April 4, 2018) - In a new study published today in the Astrophysical Journal, researchers from New York University Abu Dhabi and NASA's Jet Propulsion Laboratory (JPL) in Pasadena, CA, share new findings about how the presence of "giant" planets (between 10 and 1000 times as large as the Earth) affects potentially habitable neighbors that would be discovered with the next generation of ground-based and space-borne telescopes.

Artificial intelligence helps to predict likelihood of life on other worlds

Quote
Developments in artificial intelligence may help us to predict the probability of life on other planets, according to new work by a team based at Plymouth University. The study uses artificial neural networks (ANNs) to classify planets into five types, estimating a probability of life in each case, which could be used in future interstellar exploration missions. The work is presented at the European Week of Astronomy and Space Science (EWASS) in Liverpool on 4 April by Mr Christopher Bishop.

Post by: eeergo on 04/05/2018 01:57 PM
Extraordinary compendium of 8 protoplanetary disks imaged by ESO's SPHERE in the TTauri region:

https://arxiv.org/pdf/1803.10882.pdf
Post by: Star One on 04/05/2018 08:42 PM
Quote
A Columbia University-led team of astrophysicists has discovered a dozen black holes gathered around Sagittarius A* (Sgr A*), the supermassive black hole in the center of the Milky Way Galaxy. The finding is the first to support a decades-old prediction, opening up myriad opportunities to better understand the universe.

"Everything you'd ever want to learn about the way big black holes interact with little black holes, you can learn by studying this distribution," said Columbia Astrophysicist Chuck Hailey, co-director of the Columbia Astrophysics Lab and lead author on the study. "The Milky Way is really the only galaxy we have where we can study how supermassive black holes interact with little ones because we simply can't see their interactions in other galaxies. In a sense, this is the only laboratory we have to study this phenomenon."

http://chandra.harvard.edu/press/18_releases/press_040418.html

eso1810 — Photo Release

Quote
MUSE data points to isolated neutron star beyond our galaxy

5 April 2018

Quote
New images from ESO’s Very Large Telescope in Chile and other telescopes reveal a rich landscape of stars and glowing clouds of gas in one of our closest neighbouring galaxies, the Small Magellanic Cloud. The pictures have allowed astronomers to identify an elusive stellar corpse buried among filaments of gas left behind by a 2000-year-old supernova explosion. The MUSE instrument was used to establish where this elusive object is hiding, and existing Chandra X-ray Observatory data confirmed its identity as an isolated neutron star.

http://www.eso.org/public/news/eso1810/

MIPT physicists design a model of Martian winter

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A team of researchers from MIPT and their German and Japanese colleagues have designed a numerical model of the annual water cycle in the Martian atmosphere. Previously, the scientists focused their research on relatively large airborne dust particles that serve as water condensation nuclei on Mars. In this study, the MIPT team expanded the analysis to include smaller particles that are more elusive. As a result, the calculations turned out to be more accurate and consistent with the data obtained from Mars orbiters. The paper was published in the Journal of Geophysical Research: Planets.

Post by: Star One on 04/06/2018 07:52 PM
Hunting for dark matter in the smallest galaxies in the universe

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Astrophysicists from the University of Surrey and the University of Edinburgh have created a new method to measure the amount of dark matter at the centre of tiny "dwarf" galaxies.

Giant solar tornadoes put researchers in a spin

Quote
Despite their appearance solar tornadoes are not rotating after all, according to a team of scientists. A new analysis of these gigantic structures, each one several times the size of the Earth, indicates that they may have been misnamed because scientists have so far only been able to observe them using 2-dimensional images.

https://www.sciencedaily.com/releases/2018/04/180405223410.htm
Post by: jebbo on 04/09/2018 07:08 AM
The First Naked-Eye Superflare Detected from Proxima Centauri

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Proxima b is a terrestrial-mass planet in the habitable-zone of Proxima Centauri. Proxima Centauri's high stellar activity however casts doubt on the habitability of Proxima b: sufficiently bright and frequent flares and any associated proton events may destroy the planet's ozone layer, allowing lethal levels of UV flux to reach its surface. In March 2016, the Evryscope observed the first naked-eye-visible superflare detected from Proxima Centauri. Proxima increased in brightness by a factor of ~68 during the superflare and released a bolometric energy of 10^33.5 erg, ~10X larger than any previously-detected flare from Proxima. Over the last two years the Evryscope has recorded 23 other large Proxima flares ranging in bolometric energy from 10^30.6 erg to 10^32.4 erg; coupling those rates with the single superflare detection, we predict at least five superflares occur each year. Simultaneous high-resolution HARPS spectroscopy during the Evryscope superflare constrains the superflare's UV spectrum and any associated coronal mass ejections. We use these results and the Evryscope flare rates to model the photochemical effects of NOx atmospheric species generated by particle events from this extreme stellar activity, and show that the repeated flaring is sufficient to reduce the ozone of an Earth-like atmosphere by 90% within five years. We estimate complete depletion occurs within several hundred kyr. The UV light produced by the Evryscope superflare therefore reached the surface with ~100X the intensity required to kill simple UV-hardy microorganisms, suggesting that life would struggle to survive in the areas of Proxima b exposed to these flares

https://arxiv.org/abs/1804.02001 (https://arxiv.org/abs/1804.02001)

Wow!
Post by: Star One on 04/09/2018 04:26 PM
South Africa’s MeerKAT radio telescope observes a rare burst of activity from an exotic star, demonstrating outstanding capabilities as a new instrument for scientific exploration

Quote
6 April 2018
An article published today in The Astrophysical Journal presents the study of a magnetar – a star that is one of the most magnetic objects known in the universe – that awoke in 2017 from a 3-year slumber. Radio observations that could only be made with MeerKAT, a telescope being built in the Northern Cape province of South Africa, triggered observations with NASA X-ray telescopes orbiting the Earth. This first publication in the scientific literature of astronomical discoveries requiring the use of MeerKAT heralds its arrival into the stable of world-class research instruments.

Cosmic magnetic fields with astonishing order

Quote
Modern radio telescopes unearth structures that nobody has ever expected.

http://news.rub.de/english/press-releases/2018-04-05-astronomy-cosmic-magnetic-fields-astonishing-order
Post by: leovinus on 04/10/2018 08:26 PM
Dark matter 'missing' in a galaxy far, far away

Quote
Galaxies and dark matter go hand in hand; you typically don't find one without the other. So when researchers uncovered a galaxy, known as NGC1052-DF2, that is almost completely devoid of the stuff, they were shocked.

https://m.phys.org/news/2018-03-dark-galaxy.html

A bit of context makes this even more interesting. Two years ago, the same author with the same instrument found a galaxy which was conjectured to consist of 99.9% dark matter https://www.space.com/33850-weird-galaxy-is-mostly-dark-matter.html (https://www.space.com/33850-weird-galaxy-is-mostly-dark-matter.html). In other words, we find galaxies with extreme mixing ratios <0..99.9> for matter and dark matter, and it seems more than just one example.

Interesting discussion of this discovery at http://backreaction.blogspot.com/2018/04/no-that-galaxy-without-dark-matter-has.html (http://backreaction.blogspot.com/2018/04/no-that-galaxy-without-dark-matter-has.html).
Post by: Star One on 04/10/2018 08:35 PM

Massive Stars as Major Factories of Galactic Cosmic Rays

Felix Aharonian, Ruizhi Yang, Emma de Oña Wilhelmi
(Submitted on 6 Apr 2018)
We report a remarkable constancy of the energy and radial distribution of the CR density, w(E,r)∝E−2.3r−1, derived around the prominent galactic clusters Westerlund 1, Westerlund 2, Cyg OB2, and, presumably, also towards three ultracompact clusters located in the Galactic Centre (GC). The 1/r decrement of the CR density with the distance from the star cluster is a distinct signature of continuous injection of CRs and their diffusion through ISM. The analysis of γ-ray data show that the hard energy spectra of parent protons continue up to ∼ 1 PeV, and the efficiency of conversion of kinetic energy of powerful stellar winds can be as high as 10 percent. This implies that the population of young massive stars can provide production of CRs at a rate of up to 1041 erg/s, which is sufficient to support the flux of Galactic CRs without invoking other source populations.

https://arxiv.org/abs/1804.02331
Post by: Star One on 04/10/2018 08:42 PM
Dense stellar clusters may foster black hole megamergers

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Black holes in these environments could combine repeatedly to form objects bigger than anything a single star could produce.

http://news.mit.edu/2018/dense-stellar-clusters-may-foster-black-hole-megamergers-0410
Post by: CuddlyRocket on 04/11/2018 06:23 PM
Four new 'hot Jupiter' exoplanets discovered (https://phys.org/news/2018-04-hot-jupiter-exoplanets.html) (Phys.org article)

HATS-39b, HATS-40b, HATS-41b, and HATS-42b: Three Inflated Hot Jupiters and a Super-Jupiter Transiting F Stars (https://arxiv.org/abs/1804.01623) (arXiv paper)

Quote
(Abstract)
We report the discovery of four transiting hot Jupiters from the HATSouth survey: HATS-39b, HATS-40b, HATS41b and HATS-42b. These discoveries add to the growing number of transiting planets orbiting moderately bright (12.5 < V < 13.7) F dwarf stars on short (2-5 day) periods. The planets have similar radii, ranging from 1.33(+0.29/-0.20) R_J for HATS-41b to 1.58(+0.16/-0.12) R_J for HATS-40b. Their masses and bulk densities, however, span more than an order of magnitude. HATS-39b has a mass of 0.63 +/- 0.13 M_J, and an inflated radius of 1.57 +/- 0.12 R_J, making it a good target for future transmission spectroscopic studies. HATS-41b is a very massive 9.7 +/- 1.6 M_J planet and one of only a few hot Jupiters found to date with a mass over 5 M_J. This planet orbits the highest metallicity star ([Fe/H] = 0.470 +/- 0.010) known to host a transiting planet and is also likely on an eccentric orbit. The high mass, coupled with a relatively young age (1.34 +0.31/-0.51 Gyr) for the host star, are factors that may explain why this planet's orbit has not yet circularised.
Post by: Dao Angkan on 04/11/2018 07:06 PM
https://arxiv.org/abs/1804.03476

Gl15A c, a "Super Neptune" with a period around 7600 days, along with confirmation of the 11.44 day period "Super Earth" Gl15A b. That makes it the closest known multi-planet system to Earth at ~11.7ly (This binary system is more commonly known as Groombridge 34).
Post by: Star One on 04/11/2018 07:32 PM
Disk Imagery from Nearby Young Stars

Quote
Here’s an interesting situation: Around a star designated GSC 07396-00759, a member of a multiple star system, astronomers have found an edge-on disk. Such disks are helpful ways of studying planetary evolution, as we’re looking at gas, dust and planetesimals that represent a planetary system in the process of formation. But at GSC 07396-00759, the disk is more evolved than the gas-rich disk around the T Tauri star in the same system. In other words, we have two stars evidently of the same age whose disks show a different evolutionary pace.

https://www.centauri-dreams.org/2018/04/11/disk-imagery-from-nearby-young-stars/

After 30 years of R&D, breakthrough announced in dark matter detection technology, definitive search to begin for axion particles

Quote
This week, the Axion Dark Matter Experiment (ADMX) unveiled a new result, published in the journal Physical Review Letters, that places it in a category of one: it is the world’s first and only experiment to have achieved the necessary sensitivity to “hear” the telltale signs of dark matter axions. This technological breakthrough is the result of more than 30 years of research and development, with the latest piece of the puzzle coming in the form of a quantum-enabled device that allows ADMX to listen for axions more closely than any experiment ever built.

Saturn's formation and early evolution at the origin of Jupiter's massive moons

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The four massive Galilean satellites are believed to have formed within a circumplanetary disk during the last stages of Jupiter's formation. While the existence of a circum-jovian disk is supported by hydrodynamic simulations, no consensus exists regarding the origin and delivery mechanisms of the building blocks of the forming satellites. The opening of a gap in the circumsolar disk would have efficiently isolated Jupiter from the main sources of solid material. However, a reservoir of planetesimals should have existed at the outer edge of Jupiter's gap, where solids were trapped and accumulated over time. Here we show that the formation of Saturn's core within this reservoir, or its prompt inward migration, allows planetesimals to be redistributed from this reservoir towards Jupiter and the inner Solar System, thereby providing enough material to form the Galilean satellites and to populate the Main Belt with primitive asteroids. We find that the orbit of planetesimals captured within the circumjovian disk are circularized through friction with gas in a compact system comparable to the current radial extent of the Galilean satellites. The decisive role of Saturn in the delivery mechanism has strong implications for the occurrence of massive moons around extrasolar giant planets as they would preferentially form around planets within multiple planet systems.

https://arxiv.org/abs/1804.02892

The H.E.S.S. Galactic plane survey

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We present the results of the most comprehensive survey of the Galactic plane in very high-energy (VHE) gamma-rays, including a public release of Galactic sky maps, a catalog of VHE sources, and the discovery of 16 new sources of VHE gamma-rays. The High Energy Spectroscopic System (H.E.S.S.) Galactic plane survey (HGPS) was a decade-long observation program carried out by the H.E.S.S. I array of Cherenkov telescopes in Namibia from 2004 to 2013. The observations amount to nearly 2700 h of data, covering the Galactic plane at longitudes from l = 250 deg to 65 deg and latitudes |b| < 3 deg. In addition to the unprecedented spatial coverage, the HGPS also features a relatively high angular resolution (0.08 deg), sensitivity (1.5% Crab flux for point-like sources), and energy range (0.2-100 TeV). We constructed a source catalog with a systematic procedure for both source detection and characterization of morphology and spectrum. We present this method, including the introduction of a model component to account for unresolved, large-scale emission along the Galactic plane. In total, the resulting HGPS catalog contains 78 VHE sources, of which 14 are not reanalyzed here. Where possible, we provide a firm identification of the VHE source or plausible associations with sources in other astronomical catalogs. We also studied the characteristics of the VHE sources with source parameter distributions. 16 new sources were previously unknown or unpublished, and we individually discuss their identifications or possible associations. We firmly identified 31 sources as pulsar wind nebulae (PWNe), supernova remnants (SNRs), composite SNRs, or gamma-ray binaries. Among the 47 sources not yet identified, most of them (36) have possible associations with cataloged objects, notably PWNe and energetic pulsars that could power VHE PWNe.

https://arxiv.org/abs/1804.02432

Weave: a semicoherent search implementation for continuous gravitational waves

Quote
All-sky surveys for isolated continuous gravitational waves present a significant data-analysis challenge. Semicoherent search methods are commonly used to efficiently perform the computationally-intensive task of searching for these weak signals in the noisy data of gravitational-wave detectors such as LIGO and Virgo. We present a new implementation of a semicoherent search method, Weave, that for the first time makes full use of a parameter-space metric to generate search templates in the correct resolution, combined with optimal lattices to minimize the required number of templates and hence the computational cost of the search. We describe the implementation of Weave and associated design choices, and characterize its behavior using semi-analytic models.

https://arxiv.org/abs/1804.03392
Post by: Star One on 04/11/2018 08:27 PM
Tour of the Moon in 4K

Our Sun: Three Different Wavelengths

From March 20-23, 2018, NASA's Solar Dynamics Observatory captured three sequences of our Sun in three different extreme ultraviolet wavelengths. The resulting images illustrate how different features that appear in one sequence are difficult, if not impossible, to see in the others.

In the red sequence (304 Angstroms), we can see very small spicules - jets of solar material - and some small prominences at the Sun's edge, which are not easy to see in the other two sequences. In the second sequence (193 Angstroms), we can readily observe the large and dark coronal hole, though it is difficult to make out in the others. In the third (171 wavelengths), we can see strands of plasma waving above the surface, especially above the one small, but bright, active region near the right edge. These are just three of the ten extreme ultraviolet wavelengths in which SDO images the Sun every 12 seconds, every day.

https://www.nasa.gov/image-feature/our-sun-three-different-wavelengths
Post by: Star One on 04/12/2018 08:16 PM
Captured! Radio telescope records a rare 'glitch' in a pulsar's regular pulsing beat

Quote
Pulsars are rapidly rotating neutron stars and sometimes they abruptly increase their rotation rate. This sudden change of spin rate is called a “glitch” and I was part of a team that recorded one happening in the Vela Pulsar, with the results published today in Nature.

Approximately 5-6% of pulsars are known to glitch. The Vela pulsar is perhaps the most famous – a very southern object that spins about 11.2 times per second and was discovered by scientists in Australia in 1968.

It is 1,000 light-years away, its supernova occurred about 11,000 years ago and roughly once every three years this pulsar suddenly speeds up in rotation.

These glitches are unpredictable, and one has never been observed with a radio telescope large enough to see individual pulses.

To understand what the glitch may be, first we need to understand what makes a pulsar.

Post by: redliox on 04/15/2018 03:27 PM
Another astronomy news item:

TESS is due to launch in less than 24 hours; approximately 6:50 EST.
Post by: Star One on 04/17/2018 08:00 PM
Powerful new camera developed to directly image exoplanets

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University of California-Santa Barbara physicist Benjamin Mazin is leading an international team developing what they say is the world’s largest, most sophisticated superconducting camera in a bid to directly image exoplanets orbiting nearby stars.

While NASA is famed for the occasional convoluted acronym, the camera team came up with its own prize winner: DARKNESS, which stands for “DARK-speckle Near-infrared Energy-resolved Superconducting Spectrophotometer.”

“It is the first 10,000-pixel integral field spectrograph designed to overcome the limitations of traditional semiconductor detectors,” UC Santa Barbara said in a release. “It employs Microwave Kinetic Inductance Detectors that, in conjunction with a large telescope and an adaptive optics system, enable direct imaging of planets around nearby stars.”

The DARKNESS camera can take thousands of images per second without the “read noise” and other factors that affect more traditional cameras. It also can determine the wavelength and arrival time of every photon striking its detector.

“This technology will lower the contrast floor so that we can detect fainter planets,” Mazin said in the UC Santa Barbara release. “Mazin explained. “We hope to approach the photon noise limit … allowing us to see planets 100 million times fainter than the star. At those contrast levels, we can see some planets in reflected light, which opens up a whole new domain of planets to explore.

“The really exciting thing is that this is a technology pathfinder for the next generation of telescopes,” he said.

https://astronomynow.com/2018/04/16/powerful-new-camera-developed-to-image-exoplanets/
Post by: Star One on 04/17/2018 08:28 PM
Spaceflight from Super-Earths is difficult

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Many rocky exoplanets are heavier and larger than the Earth, and have higher surface gravity. This makes space-flight on these worlds very challenging, because the required fuel mass for a given payload is an exponential function of planetary surface gravity, ∼3.3exp(g0). We find that chemical rockets still allow for escape velocities on Super-Earths up to 10x Earth mass. More massive rocky worlds, if they exist, would require other means to leave the planet, such as nuclear propulsion.

https://arxiv.org/abs/1804.04727

A Search for Dark Matter Annihilation in the Milky Way Halo

Quote
The Milky Way halo is the brightest source of dark matter annihilation on the sky. Indeed, the potential strength of the Galactic dark matter signal can supersede that expected from dwarf galaxies and galaxy groups even in regions away from the Inner Galaxy. In this Letter, we present the results of a search for dark matter annihilation in the smooth Milky Way halo for |b|>20∘ and r<50∘ using 413 weeks of Fermi Pass 8 data within the energy range of ∼0.8-50 GeV. We exclude thermal dark matter with mass below ∼70 GeV that annihilates to bb¯ at the 95% confidence level, providing the strongest limits on the annihilation cross section in this mass range. We explore how these limits depend on uncertainties in cosmic-ray foregrounds by varying over a set of reasonable models. These results exclude the region of dark matter parameter space that is consistent with the excess of ∼GeV photons observed at the Galactic Center for the bb¯ annihilation channel and, for the first time, put the τ+τ− explanation under tension.

https://arxiv.org/abs/1804.04132

Earth as an Exoplanet

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The search for habitable and inhabited environments beyond our planet commonly focuses on analogs to Earth, especially in the case of exoplanets. Observations from ground-based facilities, satellites, and spacecraft have yielded a rich collection of data that can be used to effectively view a distant Earth within the context of exoplanet characterization. Application of planetary and exoplanetary remote sensing techniques to these datasets then enables the development of approaches to detecting signatures of habitability and life on other worlds. In addition, an array of models have also been used to simulate exoplanet-like datasets for the distant Earth, thereby providing insights that are often complementary to those from existing observations. Of course, Earth's atmosphere and surface environment has evolved substantially in the 4.5 billion years since our planet formed. A combination of in situ geological and bio-geochemical modeling studies of our planet have provided glimpses of environments that, while technically bellonging to our Earth, are seemingly alien worlds. Understanding the myriad ways Earth has been habitable and inhabited, coupled with remote sensing approaches honed on the distant Earth, provides a key guide to recognizing potentially life-bearing environments in distant planetary systems.

https://arxiv.org/abs/1804.04138

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We study shadows cast by a certain class of rotating wormholes and point out the crucial role of a rotating wormhole throat in the formation of a shadow, a crucial point overlooking of which has resulted erroneous results in the earlier studies on shadows of the same class of rotating wormholes. We explore the dependence of the shadows on the spin of the wormholes. We compare our results with that of the Kerr black hole. With increasing values of the spin, the shapes of the wormhole shadows start deviating considerably from that of the black hole. Such considerable deviation, if detected in future observations, may possibly indicate the presence of a wormhole. In other words, the results obtained here indicate that, through the observations of their shadows, the wormholes which are considered in this work and have reasonable spin, can be distinguished from a black hole.

https://arxiv.org/abs/1803.11422

Highly Volcanic Exoplanets, Lava Worlds, and Magma Ocean Worlds: An Emerging Class of Dynamic Exoplanets of Significant Scientific Priority

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Highly volcanic exoplanets, which can be variously characterized as 'lava worlds', 'magma ocean worlds', or 'super-Ios' are high priority targets for investigation. The term 'lava world' may refer to any planet with extensive surface lava lakes, while the term 'magma ocean world' refers to planets with global or hemispherical magma oceans at their surface. 'Highly volcanic planets', including super-Ios, may simply have large, or large numbers of, active explosive or extrusive volcanoes of any form. They are plausibly highly diverse, with magmatic processes across a wide range of compositions, temperatures, activity rates, volcanic eruption styles, and background gravitational force magnitudes. Worlds in all these classes are likely to be the most characterizable rocky exoplanets in the near future due to observational advantages that stem from their preferential occurrence in short orbital periods and their bright day-side flux in the infrared. Transit techniques should enable a level of characterization of these worlds analogous to hot Jupiters. Understanding processes on highly volcanic worlds is critical to interpret imminent observations. The physical states of these worlds are likely to inform not just geodynamic processes, but also planet formation, and phenomena crucial to habitability. Volcanic and magmatic activity uniquely allows chemical investigation of otherwise spectroscopically inaccessible interior compositions. These worlds will be vital to assess the degree to which planetary interior element abundances compare to their stellar hosts, and may also offer pathways to study both the very young Earth, and the very early form of many silicate planets where magma oceans and surface lava lakes are expected to be more prevalent. We suggest that highly volcanic worlds may become second only to habitable worlds in terms of both scientific and public long-term interest.

https://arxiv.org/abs/1804.05110
Post by: Star One on 04/18/2018 07:57 PM
Study: Diamond from the sky may have come from 'lost planet'

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Fragments of a meteorite that fell to Earth about a decade ago provide compelling evidence of a lost planet that once roamed our solar system, according to a study published Tuesday.

https://phys.org/news/2018-04-diamond-sky-lost-planet.amp?
Post by: Star One on 04/19/2018 07:37 PM
The GALAH Survey: Second Data Release

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The Galactic Archaeology with HERMES (GALAH) survey is a large-scale stellar spectroscopic survey of the Milky Way and designed to deliver chemical information complementary to a large number of stars covered by the Gaia mission. We present the GALAH second public data release (GALAH DR2) containing 342,682 stars. For these stars, the GALAH collaboration provides stellar parameters and abundances for up to 23 elements to the community. Here we present the target selection, observation, data reduction and detailed explanation of how the spectra were analysed to estimate stellar parameters and element abundances. For the stellar analysis, we have used a multi-step approach. We use the physics-driven spectrum synthesis of Spectroscopy Made Easy (SME) to derive stellar labels (Teff, logg, [Fe/H], [X/Fe], vmic, vsini, AKS) for a representative training set of stars. This information is then propagated to the whole survey with the data-driven method of The Cannon. Special care has been exercised in the spectral synthesis to only consider spectral lines that have reliable atomic input data and are little affected by blending lines. Departures from local thermodynamic equilibrium (LTE) are considered for several key elements, including Li, O, Na, Mg, Al, Si, and Fe, using 1D MARCS stellar atmosphere models. Validation tests including repeat observations, Gaia benchmark stars, open and globular clusters, and K2 asteroseismic targets lend confidence in our methods and results. Combining the GALAH DR2 catalogue with the kinematic information from Gaia will enable a wide range of Galactic Archaeology studies, with unprecedented detail, dimensionality, and scope.

https://arxiv.org/abs/1804.06041

Superflares on Giant Stars

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The Kepler mission identified huge flares on various stars including some of solar type. These events are substantially more energetic than solar flares, and so they are referred to as superflares. Even a small probability of such a superflare on the Sun would be a menace to modern society. A flare comparable in energy with that of superflares was observed on 24th and 25th September on the binary HK Lac. Unlike the Kepler stars, there are observations of differential rotation for HK Lac. This differential rotation appears to be anti-solar. For anti-solar differential rotation, dynamo models can give magnetic activity waves of dipole symmetry as well as quasi-stationary magnetic configurations with quadrupole symmetry. The magnetic energy of such stationary configurations is usually about two orders of magnitude higher than that associated with activity waves. We believe that this mechanism could provide sufficient energy to produce superflares on late type stars, and present some simple models in support of this idea.

https://arxiv.org/abs/1804.06315
Post by: Star One on 04/20/2018 08:10 PM

An Unexpected Dip in the Solar Gamma-Ray Spectrum

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The solar disk is a bright source of multi-GeV gamma rays, due to the interactions of hadronic cosmic rays with the solar atmosphere. However, the underlying production mechanism is not understood, except that its efficiency must be greatly enhanced by magnetic fields that redirect some cosmic rays from ingoing to outgoing before they interact. To elucidate the nature of this emission, we perform a new analysis of solar atmospheric gamma rays with 9 years of Fermi-LAT data, which spans nearly the full 11-year solar cycle. We detect significant gamma-ray emission from the solar disk from 1 GeV up to ≳200 GeV. The overall gamma-ray spectrum is much harder (∼E−2.2γ) than the cosmic-ray spectrum (∼E−2.7CR). We find a clear anticorrelation between the solar cycle phase and the gamma-ray flux between 1-10 GeV. Surprisingly, we observe a spectral dip between ∼30-50 GeV in an otherwise power-law spectrum. This was not predicted, is not understood, and may provide crucial clues to the gamma-ray emission mechanism. The flux above 100 GeV, which is brightest during the solar minimum, poses exciting opportunities for HAWC, LHAASO, IceCube, and KM3NeT.

https://arxiv.org/abs/1804.06846