Author Topic: Exoplanets And Stars Thread  (Read 18115 times)

Offline Star One

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Exoplanets And Stars Thread
« 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
« Last Edit: 06/28/2017 09:45 AM by Star One »

Offline Star One

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Exoplanet Thread
« Reply #1 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
« Last Edit: 01/26/2017 06:57 PM by Star One »

Offline ikke666

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Re: Exoplanet Thread
« Reply #2 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,...)

Offline testguy

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Re: Exoplanet Thread
« Reply #3 on: 01/27/2017 05:29 PM »
Try this.  Updates daily.

http://exoplanet.eu/catalog/

Offline hop

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Re: Exoplanet Thread
« Reply #4 on: 01/28/2017 06:00 AM »
There's also the NASA Exoplanet archive http://exoplanetarchive.ipac.caltech.edu/

Offline Star One

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Re: Exoplanet Thread
« Reply #5 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/

Offline ikke666

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Re: Exoplanet Thread
« Reply #6 on: 01/28/2017 03:55 PM »
thanks for the sites  ;D

Offline Star One

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Re: Exoplanet Thread
« Reply #7 on: 02/02/2017 08:38 PM »

Offline Star One

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Re: Exoplanet Thread
« Reply #8 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#

Offline Star One

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Exoplanet Thread
« Reply #9 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

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« Last Edit: 02/15/2017 08:05 PM by Star One »

Offline Mongo62

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Re: Exoplanet Thread
« Reply #10 on: 02/28/2017 07:23 PM »
Towards Detection of Exoplanetary Rings Via Transit Photometry: Methodology and a Possible Candidate

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.

Offline Star One

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Exoplanet Thread
« Reply #11 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
« Last Edit: 03/10/2017 06:51 PM by Star One »

Offline jebbo

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Re: Exoplanet Thread
« Reply #12 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

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

Offline Bynaus

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Re: Exoplanet Thread
« Reply #13 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.

Offline jebbo

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Re: Exoplanet Thread
« Reply #14 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
« Last Edit: 03/13/2017 05:50 PM by jebbo »

Offline Star One

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Re: Exoplanet Thread
« Reply #15 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.

http://physicstoday.scitation.org/doi/abs/10.1063/PT.3.3494#.WMbXbKSwOf8.twitter

Offline Star One

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Exoplanet Thread
« Reply #16 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
« Last Edit: 03/14/2017 01:48 PM by Star One »

Offline Star One

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Re: Exoplanet Thread
« Reply #17 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

Offline Bynaus

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Re: Exoplanet Thread
« Reply #18 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.

Offline Star One

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Re: Exoplanet Thread
« Reply #19 on: 03/28/2017 08:17 PM »

Offline CuddlyRocket

Re: Exoplanet Thread
« Reply #20 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⊕.

Offline Star One

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Re: Exoplanet Thread
« Reply #21 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/

Offline Star One

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Exoplanet Thread
« Reply #22 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
« Last Edit: 04/06/2017 08:37 PM by Star One »

Offline CuddlyRocket

Re: Exoplanet Thread
« Reply #23 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.

Offline jebbo

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Re: Exoplanet Thread
« Reply #24 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
« Last Edit: 04/09/2017 04:49 PM by jebbo »

Offline CuddlyRocket

Re: Exoplanet Thread
« Reply #25 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)

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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.

Quote
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.

Offline Bynaus

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Re: Exoplanet Thread
« Reply #26 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)

Quote
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.

Quote
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.
« Last Edit: 04/18/2017 06:54 AM by Bynaus »

Offline Star One

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Re: Exoplanet Thread
« Reply #27 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

Offline Star One

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Re: Exoplanet Thread
« Reply #28 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/

Offline Star One

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Re: Exoplanet Thread
« Reply #29 on: 04/26/2017 06:52 PM »
Speculations on Habitable Zone Waterworlds

Quote
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

Offline CuddlyRocket

Re: Exoplanet Thread
« Reply #30 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! :)

Offline Star One

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Re: Exoplanet Thread
« Reply #31 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.

Offline Star One

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Re: Exoplanet Thread
« Reply #32 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/

Offline Star One

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Re: Exoplanet Thread
« Reply #33 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

Offline Star One

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Exoplanet Thread
« Reply #34 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

More info to the above on this link.

http://www.centauri-dreams.org/?p=37606
« Last Edit: 05/03/2017 05:37 PM by Star One »

Offline Star One

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Re: Exoplanet Thread
« Reply #35 on: 05/10/2017 08:46 PM »
Exploring the Planet / Brown Dwarf Boundary

http://www.centauri-dreams.org/?p=37665

Offline missinglink

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Re: Exoplanet Thread
« Reply #36 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

Offline gospacex

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Re: Exoplanet Thread
« Reply #37 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...

Offline Star One

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Re: Exoplanet Thread
« Reply #38 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.

Offline Torbjorn Larsson, OM

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Re: Exoplanet Thread
« Reply #39 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."

Offline missinglink

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Re: Exoplanet Thread
« Reply #40 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.

Thanks for answers received thus far.
« Last Edit: 05/11/2017 08:36 PM by missinglink »

Offline dror

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Re: Exoplanet Thread
« Reply #41 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.
"If we crave some cosmic purpose, then let us find ourselves a worthy goal. "
Carl Sagan, Pale Blue Dot

Offline Star One

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Re: Exoplanet Thread
« Reply #42 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

Offline missinglink

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Re: Exoplanet Thread
« Reply #43 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.

Offline gospacex

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Re: Exoplanet Thread
« Reply #44 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!
« Last Edit: 05/12/2017 05:50 PM by gospacex »

Offline Oli

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Re: Exoplanet Thread
« Reply #45 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.

Offline TakeOff

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Re: Exoplanet Thread
« Reply #46 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.

Offline TakeOff

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Re: Exoplanet Thread
« Reply #47 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.

Offline hop

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Re: Exoplanet Thread
« Reply #48 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

There is already a thread about for the gravitational focus telescope concept:  http://forum.nasaspaceflight.com/index.php?topic=27490.0

Offline CuddlyRocket

Re: Exoplanet Thread
« Reply #49 on: 05/16/2017 08:30 PM »
K2-106, a system containing a metal rich planet and a planet of lower density (arXiv)

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!

Offline Star One

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Re: Exoplanet Thread
« Reply #50 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

Offline Star One

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Re: Exoplanet Thread
« Reply #51 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/

Offline Star One

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Exoplanet Thread
« Reply #52 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
« Last Edit: 05/30/2017 11:33 AM by Star One »

Offline hop

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Re: Exoplanet Thread
« Reply #53 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 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.

Offline CuddlyRocket

Re: Exoplanet Thread
« Reply #54 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!

Offline Star One

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Re: Exoplanet Thread
« Reply #55 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

Offline Star One

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Exoplanet Thread
« Reply #56 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.
« Last Edit: 06/05/2017 04:19 PM by Star One »

Offline Star One

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Re: Exoplanet Thread
« Reply #57 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

Offline Star One

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Re: Exoplanet Thread
« Reply #58 on: 06/09/2017 04:51 PM »
 Planet Formation around TRAPPIST-1

https://www.centauri-dreams.org/?p=37917

Offline CuddlyRocket

Re: Exoplanet Thread
« Reply #59 on: 06/13/2017 02:44 AM »
Two new massive planets detected around the star HD 27894 (Phys.org article).
Three planets around HD 27894 (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.

Offline Star One

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Exoplanet Thread
« Reply #60 on: 06/13/2017 08:24 AM »
I still can't help wonder if there are more planets in the large gap.
« Last Edit: 06/13/2017 08:31 AM by Star One »

Offline Bynaus

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Re: Exoplanet Thread
« Reply #61 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).
« Last Edit: 06/13/2017 08:37 AM by Bynaus »

Offline Star One

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Re: Exoplanet Thread
« Reply #62 on: 06/13/2017 08:35 PM »
New evidence that all stars are born in pairs

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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/

Offline Star One

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Re: Exoplanet Thread
« Reply #63 on: 06/14/2017 07:46 PM »
Mistaken brown dwarf is actually two planets orbiting each other

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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

Offline CuddlyRocket

Re: Exoplanet Thread
« Reply #64 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.)

Offline clongton

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Re: Exoplanet Thread
« Reply #65 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.
« Last Edit: 06/16/2017 12:22 AM by clongton »
Chuck - DIRECT co-founder
I started my career on the Saturn-V F-1A engine

Offline jebbo

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Re: Exoplanet Thread
« Reply #66 on: 06/19/2017 09:37 AM »
An announcement from the Pale Red Dot team is expected at 11am CET:

https://twitter.com/Pale_red_dot/status/876530355523776513

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

--- Tony

Offline Alpha_Centauri

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Re: Exoplanet Thread
« Reply #67 on: 06/19/2017 10:22 AM »
Sounds like it is just announcing the search rather than any discoveries yet.

Offline jebbo

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Re: Exoplanet Thread
« Reply #68 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
« Last Edit: 06/19/2017 10:42 AM by jebbo »

Offline Star One

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Exoplanet Thread
« Reply #69 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.
« Last Edit: 06/19/2017 10:50 AM by Star One »

Offline Alpha_Centauri

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Re: Exoplanet Thread
« Reply #70 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.
« Last Edit: 06/19/2017 11:03 AM by Alpha_Centauri »

Offline jebbo

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Re: Exoplanet Thread
« Reply #71 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

Offline Star One

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Exoplanet Thread
« Reply #72 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?
« Last Edit: 06/19/2017 11:44 AM by Star One »

Offline jebbo

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Re: Exoplanet Thread
« Reply #73 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

Offline Star One

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Exoplanet Thread
« Reply #74 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?
« Last Edit: 06/19/2017 12:02 PM by Star One »

Offline jebbo

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Re: Exoplanet Thread
« Reply #75 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
« Last Edit: 06/19/2017 12:27 PM by jebbo »

Offline Star One

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Re: Exoplanet Thread
« Reply #76 on: 06/19/2017 08:34 PM »
Article on the same.

Pale Red Dot: Campaign 2

https://www.centauri-dreams.org/?p=37964

Offline CuddlyRocket

Re: Exoplanet Thread
« Reply #77 on: 06/20/2017 06:11 AM »
Cross-posting to provide links to relevant posts in the Kepler Updates thread:

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.

Offline jebbo

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Re: Exoplanet Thread
« Reply #78 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, and predates the latest DR25 release.

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

--- Tony




Offline Alpha_Centauri

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Re: Exoplanet Thread
« Reply #79 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).
« Last Edit: 06/20/2017 11:17 AM by Alpha_Centauri »

Offline jebbo

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Re: Exoplanet Thread
« Reply #80 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

Offline Alpha_Centauri

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Re: Exoplanet Thread
« Reply #81 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
« Last Edit: 06/20/2017 12:52 PM by Alpha_Centauri »

Offline Star One

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Exoplanet Thread
« Reply #82 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.
« Last Edit: 06/20/2017 07:22 PM by Star One »

Offline Star One

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Re: Exoplanet Thread
« Reply #83 on: 06/23/2017 08:52 PM »

Offline Star One

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Exoplanet Thread
« Reply #84 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.
« Last Edit: 06/27/2017 10:57 AM by Star One »

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Re: Exoplanets And Stars Thread
« Reply #86 on: 06/28/2017 09:47 AM »
Groundbreaking discovery confirms existence of orbiting supermassive black holes

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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.


Read more at: https://phys.org/news/2017-06-groundbreaking-discovery-orbiting-supermassive-black.html#jCp

Offline Star One

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Re: Exoplanets And Stars Thread
« Reply #87 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

Offline Star One

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Re: Exoplanets And Stars Thread
« Reply #88 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

Offline Star One

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Exoplanets And Stars Thread
« Reply #89 on: 07/06/2017 07:41 PM »
A cosmic barbecue: Researchers spot 60 new 'hot Jupiter' candidates

https://www.eurekalert.org/pub_releases/2017-07/yu-acb070617.php
« Last Edit: 07/06/2017 08:01 PM by Star One »

Offline CuddlyRocket

Re: Exoplanets And Stars Thread
« Reply #90 on: 07/07/2017 05:40 AM »
^^ Paper on arXiv

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.

Offline Star One

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Re: Exoplanets And Stars Thread
« Reply #91 on: 07/07/2017 06:59 AM »
^^ Paper on arXiv

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?

Offline Star One

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Re: Exoplanets And Stars Thread
« Reply #92 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

Offline CuddlyRocket

Re: Exoplanets And Stars Thread
« Reply #93 on: 07/09/2017 07:57 PM »
^^ Paper on arXiv

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'.

Offline Star One

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Re: Exoplanets And Stars Thread
« Reply #94 on: 07/09/2017 07:59 PM »
^^ Paper on arXiv

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.

Offline CuddlyRocket

Re: Exoplanets And Stars Thread
« Reply #95 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!

Offline Star One

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Re: Exoplanets And Stars Thread
« Reply #96 on: 07/12/2017 09:04 AM »
Hidden Stars May Make Planets Appear Smaller

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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."

For more information about exoplanets, visit:

https://exoplanets.nasa.gov

https://www.jpl.nasa.gov/news/news.php?release=2017-187&rn=news.xml&rst=6893

Offline Star One

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Exoplanets And Stars Thread
« Reply #97 on: 07/12/2017 01:17 PM »
Eight planetary systems found hosting 20 super-Earth & Neptune-mass companions

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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.

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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.

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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/
« Last Edit: 07/12/2017 01:29 PM by Star One »

Offline Star One

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Re: Exoplanets And Stars Thread
« Reply #98 on: 07/12/2017 07:25 PM »
Smallest-ever star discovered by astronomers

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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/

Offline Star One

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Re: Exoplanets And Stars Thread
« Reply #99 on: 07/13/2017 07:20 PM »
More to Life Than the Habitable Zone

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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

Offline Star One

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Re: Exoplanets And Stars Thread
« Reply #100 on: 07/18/2017 07:40 PM »
Why We Need a New Type of SETI Instrument

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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

Offline Star One

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Re: Exoplanets And Stars Thread
« Reply #101 on: 07/19/2017 07:04 PM »
“Variable and polarized radio emission from the T6 brown dwarf WISEP J112254.73+255021.5”

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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.

https://newton.cx/~peter/2017/07/variable-and-polarized-radio-emission-from-the-t6-brown-dwarf-wisep-j112254-73255021-5/

Offline Star One

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Exoplanets And Stars Thread
« Reply #102 on: 07/19/2017 07:53 PM »
Astronomers discover Earth-sized exoplanet with very short orbital period

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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.

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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
« Last Edit: 07/19/2017 07:56 PM by Star One »

Offline Bynaus

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Re: Exoplanets And Stars Thread
« Reply #103 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).

Offline as58

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Re: Exoplanets And Stars Thread
« Reply #104 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.
« Last Edit: 07/19/2017 09:20 PM by as58 »

Offline CuddlyRocket

Re: Exoplanets And Stars Thread
« Reply #105 on: 07/20/2017 03:20 AM »
Astronomers discover Earth-sized exoplanet with very short orbital period

From the arXiv paper:

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).

Offline Star One

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Re: Exoplanets And Stars Thread
« Reply #106 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

Offline hop

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Re: Exoplanets And Stars Thread
« Reply #107 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 (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.

Offline Star One

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Exoplanets And Stars Thread
« Reply #108 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 (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.
« Last Edit: 07/26/2017 09:03 PM by Star One »

Offline hop

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Re: Exoplanets And Stars Thread
« Reply #109 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

Offline Alpha_Centauri

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Re: Exoplanets And Stars Thread
« Reply #110 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
Quote
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.
« Last Edit: 07/27/2017 10:14 AM by Alpha_Centauri »

Offline Star One

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Re: Exoplanets And Stars Thread
« Reply #111 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?

Offline Bynaus

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Re: Exoplanets And Stars Thread
« Reply #112 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.

Offline Star One

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Exoplanets And Stars Thread
« Reply #113 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.
« Last Edit: 07/27/2017 08:14 AM by Star One »

Offline Bynaus

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Re: Exoplanets And Stars Thread
« Reply #114 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.

Offline Star One

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Re: Exoplanets And Stars Thread
« Reply #115 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.

Offline Alpha_Centauri

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Re: Exoplanets And Stars Thread
« Reply #116 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/

Offline LouScheffer

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Re: Exoplanets And Stars Thread
« Reply #117 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 (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.

Offline Star One

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Re: Exoplanets And Stars Thread
« Reply #118 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/

Offline hop

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Re: Exoplanets And Stars Thread
« Reply #119 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.

Offline Star One

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Re: Exoplanets And Stars Thread
« Reply #120 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.

Offline Star One

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Re: Exoplanets And Stars Thread
« Reply #121 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/

Offline Star One

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Re: Exoplanets And Stars Thread
« Reply #122 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

Offline hop

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Re: Exoplanets And Stars Thread
« Reply #123 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


Offline Star One

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Re: Exoplanets And Stars Thread
« Reply #124 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.

Offline rubtest

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Re: Exoplanets And Stars Thread
« Reply #125 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.

Offline Star One

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Exoplanets And Stars Thread
« Reply #126 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
« Last Edit: 07/28/2017 06:52 PM by Star One »

Offline Dao Angkan

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Re: Exoplanets And Stars Thread
« Reply #127 on: 08/01/2017 02:36 AM »
Four new short-period giant planets discovered

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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.

Offline Phil Stooke

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Re: Exoplanets And Stars Thread
« Reply #128 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.

Offline Star One

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Re: Exoplanets And Stars Thread
« Reply #129 on: 08/01/2017 04:40 PM »

Exomoons: Rare in Inner Stellar Systems?

Quote
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

Offline Star One

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Exoplanets And Stars Thread
« Reply #130 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/
« Last Edit: 08/03/2017 09:06 AM by Star One »

Offline Star One

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Re: Exoplanets And Stars Thread
« Reply #131 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

Offline Star One

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Re: Exoplanets And Stars Thread
« Reply #132 on: 08/03/2017 07:53 PM »
Gravity Waves Detected In Sun's Interior Reveal Rapidly Rotating Core

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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

Offline Star One

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Re: Exoplanets And Stars Thread
« Reply #133 on: 08/04/2017 08:10 PM »
Bad News For Proxima b: An Earth-Like Atmosphere Might Not Survive There

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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!

https://www.universetoday.com/136641/bad-news-proxima-b-earth-like-atmosphere-might-not-survive/amp/

Offline Dao Angkan

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Re: Exoplanets And Stars Thread
« Reply #134 on: 08/09/2017 02:56 PM »
Four Earth-sized planets detected orbiting the nearest sun-like star





Quote
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

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.

Offline Star One

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Re: Exoplanets And Stars Thread
« Reply #135 on: 08/09/2017 06:49 PM »
Is Tau Ceti more sunlike than either of the Alpha Centauri stars then?

Offline Bob Shaw

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Re: Exoplanets And Stars Thread
« Reply #136 on: 08/09/2017 07:12 PM »
Have any planets been *really* detected around Bernard's Star? It would be rather nice!

Offline zubenelgenubi

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Re: Exoplanets And Stars Thread
« Reply #137 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.
« Last Edit: 08/09/2017 07:46 PM by zubenelgenubi »
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Offline Bynaus

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Re: Exoplanets And Stars Thread
« Reply #138 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 project is bound to find out!

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Re: Exoplanets And Stars Thread
« Reply #139 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 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?

Offline Bynaus

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Re: Exoplanets And Stars Thread
« Reply #140 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 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):
http://adsabs.harvard.edu/abs/2015csss...18..783L

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

Offline Star One

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Exoplanets And Stars Thread
« Reply #141 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 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):
http://adsabs.harvard.edu/abs/2015csss...18..783L

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.
« Last Edit: 08/09/2017 08:40 PM by Star One »

Offline Dao Angkan

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Re: Exoplanets And Stars Thread
« Reply #142 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.
« Last Edit: 08/09/2017 08:56 PM by Dao Angkan »

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Re: Exoplanets And Stars Thread
« Reply #143 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.

Offline Dao Angkan

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Re: Exoplanets And Stars Thread
« Reply #144 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.


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Re: Exoplanets And Stars Thread
« Reply #145 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.

Offline Dao Angkan

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Re: Exoplanets And Stars Thread
« Reply #146 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.




Offline Star One

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Re: Exoplanets And Stars Thread
« Reply #147 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/

Offline Star One

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Re: Exoplanets And Stars Thread
« Reply #148 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).

http://www.astronomerstelegram.org/?read=10634

Offline Star One

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Re: Exoplanets And Stars Thread
« Reply #149 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.

For more information about TRAPPIST-1, visit:

https://exoplanets.nasa.gov/trappist1

Offline Star One

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Re: Exoplanets And Stars Thread
« Reply #150 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

Offline Bynaus

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Re: Exoplanets And Stars Thread
« Reply #151 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.

Offline Star One

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Exoplanets And Stars Thread
« Reply #152 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.

Quote
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/
« Last Edit: 08/15/2017 07:35 PM by Star One »

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Re: Exoplanets And Stars Thread
« Reply #153 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

Offline Star One

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Re: Exoplanets And Stars Thread
« Reply #154 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/

Offline CuddlyRocket

Re: Exoplanets And Stars Thread
« Reply #155 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.

Unfortunately, they don't say what happened to the companion star. :(

Offline NIVbV-O77OdV-VSVN-Op-SLE7

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Re: Exoplanets And Stars Thread
« Reply #156 on: 08/18/2017 03:33 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

Just imagine a boat bobbing on water while watching something on the horizon reappear/disappear.


Offline Kesarion

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Re: Exoplanets And Stars Thread
« Reply #157 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.

Offline gospacex

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Re: Exoplanets And Stars Thread
« Reply #158 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.

Quote
  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".

Offline Star One

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Re: Exoplanets And Stars Thread
« Reply #159 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

Offline Star One

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Re: Exoplanets And Stars Thread
« Reply #160 on: 08/18/2017 07:04 PM »

Offline Star One

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Re: Exoplanets And Stars Thread
« Reply #161 on: 08/18/2017 07:23 PM »
Scientists improve brown dwarf weather forecasts

Quote
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/

Offline Star One

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Re: Exoplanets And Stars Thread
« Reply #162 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?

Offline CuddlyRocket

Re: Exoplanets And Stars Thread
« Reply #163 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.)

Offline Dao Angkan

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Re: Exoplanets And Stars Thread
« Reply #164 on: 08/18/2017 11:19 PM »
Only in as far as most stars are believed to have planets. Most of the nearest stars to 16.3 ly* still don't even have candidate planets yet.

*To 21 ly, as Wikipedia doesn't seem to have a list of stars from 16.3 - 20 ly.

Offline redliox

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Re: Exoplanets And Stars Thread
« Reply #165 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 to 16.3 ly* still don't even have candidate planets yet.

*To 21 ly, as Wikipedia doesn't seem to have a list 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.
"Let the trails lead where they may, I will follow."
-Tigatron

Offline Star One

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Re: Exoplanets And Stars Thread
« Reply #166 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?

Offline Dao Angkan

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Re: Exoplanets And Stars Thread
« Reply #167 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 to 16.3 ly* still don't even have candidate planets yet.

*To 21 ly, as Wikipedia doesn't seem to have a list 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
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).

Offline Dao Angkan

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Re: Exoplanets And Stars Thread
« Reply #168 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.

Offline Star One

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Re: Exoplanets And Stars Thread
« Reply #169 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?

Offline Alpha_Centauri

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Re: Exoplanets And Stars Thread
« Reply #170 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.
« Last Edit: 08/19/2017 02:46 PM by Alpha_Centauri »

Offline Dao Angkan

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Re: Exoplanets And Stars Thread
« Reply #171 on: 08/19/2017 03:21 PM »
There is a candidate for a Super Earth around Lalande 21185, the 6th closest main sequence star / 4th closest star system (it's missing from CuddlyRocket's list).

Offline Hungry4info3

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Re: Exoplanets And Stars Thread
« Reply #172 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.
« Last Edit: 08/19/2017 05:34 PM by Hungry4info3 »

Offline Star One

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Re: Exoplanets And Stars Thread
« Reply #173 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.

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