Author Topic: Astronomy Thread  (Read 63621 times)

Offline Star One

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Re: Astronomy Thread
« Reply #300 on: 01/09/2018 05:00 PM »
Extra-Terrestrial Hypatia Stone Rattles Solar System Status Quo

https://scienmag.com/extra-terrestrial-hypatia-stone-rattles-solar-system-status-quo/

Offline Bynaus

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Re: Astronomy Thread
« Reply #301 on: 01/09/2018 06:58 PM »
Extra-Terrestrial Hypatia Stone Rattles Solar System Status Quo

https://scienmag.com/extra-terrestrial-hypatia-stone-rattles-solar-system-status-quo/

A couple of years ago, I was co-author on a paper studying the Hypatia stone (https://arxiv.org/abs/1510.06594). The stone is clearly extraterrestrial, yes, but I think this whole story is getting blown way out of proportion in the new paper.

First, its not like carbon-dominated materials are unheard off in meteorites - we identified several possibilities in our paper, the strongest, in my opinion, being that the stone is shock-compressed (thus diamond-bearing) graphite nodule from an iron meteorite (there is actually additional support for this from the Fe, Ni, S and P phases the authors of the new paper report - all these elements are abundant in iron meteorites).

Second, the claim of a pre-solar origin would require the identification of the characteristically large isotopic anomalies, which the authors of the new paper do not report.
« Last Edit: 01/09/2018 07:01 PM by Bynaus »

Offline Star One

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Re: Astronomy Thread
« Reply #302 on: 01/09/2018 08:13 PM »
White dwarf’s inner makeup is mapped for the first time

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Astronomers have probed the inner life of a dead star. Tiny changes in a white dwarf’s brightness reveal that the stellar corpse has more oxygen in its core than expected, researchers report online January 8 in Nature. The finding could challenge theories of how stars live and die, and may have implications for measuring the expansion of the universe.

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More recent observations suggest that these so-called standard candles may not be so standard after all. If the white dwarfs that help create supernovas have varying oxygen contents, that may help explain some of the differences, Fontaine says.

Accounting for that difference may someday help reveal details of what dark energy is made of, says astrophysicist Alexei Filippenko of the University of California, Berkeley. But those implications are a long way off. “Just how much bearing it will have on cosmology remains to be seen,” he says.

https://www.sciencenews.org/article/white-dwarfs-inner-makeup-mapped-first-time

Offline fthomassy

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Re: Astronomy Thread
« Reply #303 on: 01/09/2018 10:38 PM »
Cross posting as it might relate to astronomy tracking too ...
Incredible footage of stage sep and the boostback burn.


Thanks!  That was my video. I'm hoping at some point other launch regulars who do tracking shots start to adopt my setup and software for their shots as well.  The software is very experimental, but it's freely available.  Computer, joystick, and telescope not included, of course.
gyatm . . . Fern

Offline Star One

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Re: Astronomy Thread
« Reply #304 on: 01/10/2018 07:17 PM »
Across the universe, fast radio bursts ‘shout and twist’

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An international group of astronomers has found that the Cornell-discovered fast radio burst FRB 121102 – a brief, gigantic pulse of radio waves from 3 billion light years away – passes through a veil of magnetized plasma. This causes the cosmic blasts to “shout and twist,” which will help the scientists determine the source.

The research is featured on the cover of Nature, Jan. 11.

The “shouting” represents the bursts, and the “twisting” describes a physical phenomenon called Faraday rotation, which occurs as radio waves pass through a magnetized plasma, explained James Cordes, the George Feldstein Professor of Astronomy. Measurement of the twisting provides further scientific detail on the origin of FRB 121102. The data were culled from the Arecibo Observatory in Puerto Rico and confirmed by Green Bank Observatory in West Virginia.

http://news.cornell.edu/stories/2018/01/across-universe-fast-radio-bursts-shout-and-twist

Offline Star One

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Re: Astronomy Thread
« Reply #305 on: 01/11/2018 08:52 PM »
The K2-138 System: A Near-resonant Chain of Five Sub-Neptune Planets Discovered by Citizen Scientists

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K2-138 is a moderately bright (V = 12.2, K = 10.3) main-sequence K star observed in Campaign 12 of the NASA K2 mission. It hosts five small (1.6–3.3 ${R}_{\oplus }$) transiting planets in a compact architecture. The periods of the five planets are 2.35, 3.56, 5.40, 8.26, and 12.76 days, forming an unbroken chain of near 3:2 resonances. Although we do not detect the predicted 2–5 minute transit timing variations (TTVs) with the K2 timing precision, they may be observable by higher-cadence observations with, for example, Spitzer or CHEOPS. The planets are amenable to mass measurement by precision radial velocity measurements, and therefore K2-138 could represent a new benchmark system for comparing radial velocity and TTV masses. K2-138 is the first exoplanet discovery by citizen scientists participating in the Exoplanet Explorers project on the Zooniverse platform.

http://iopscience.iop.org/article/10.3847/1538-3881/aa9be0

Offline jebbo

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Re: Astronomy Thread
« Reply #306 on: 01/12/2018 09:31 AM »
The K2-138 System: A Near-resonant Chain of Five Sub-Neptune Planets Discovered by Citizen Scientists

Yes, this is a very interesting one: the two transits at ~42 days that suggest a sixth planet are consistent with the 3/2 resonance chain ... if you skip two slots at ~18.6 days and 27.9 days

--- Tony

Offline Star One

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Re: Astronomy Thread
« Reply #307 on: 01/12/2018 09:35 AM »
The K2-138 System: A Near-resonant Chain of Five Sub-Neptune Planets Discovered by Citizen Scientists

Yes, this is a very interesting one: the two transits at ~42 days that suggest a sixth planet are consistent with the 3/2 resonance chain ... if you skip two slots at ~18.6 days and 27.9 days

--- Tony

Go and have a quick look at Professor Chris Lintott’s twitter account as he talks about that very thing on there.

Offline Star One

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Re: Astronomy Thread
« Reply #308 on: 01/12/2018 12:53 PM »
Meet the amateur astronomers who track secretive spy satellites for fun

https://www.popsci.com/zuma-spy-satellite-amateur-astronomer

Offline Star One

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Re: Astronomy Thread
« Reply #309 on: 01/12/2018 07:36 PM »
We may be able to see mountains and valleys on distant worlds

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Moiya McTier at Columbia University in New York presented her research into the embryonic field of exotopography on 11 January at a meeting of the American Astronomical Society. She says that by analysing the dip in a star’s light as a planet passes in front of it, we might be able to discern actual details about the planet’s landscape.

None of the rocky planets in our solar system are perfectly round: there are mountains, canyons, craters and other features that carve elevations high and low across a surface. So why shouldn’t there be similar features on planets orbiting other stars?

McTier took US Geological Survey maps of our four terrestrial planets and the Moon to determine what their light curve around

https://www.newscientist.com/article/2158466-we-may-be-able-to-see-mountains-and-valleys-on-distant-worlds

Offline CuddlyRocket

Re: Astronomy Thread
« Reply #310 on: 01/13/2018 05:53 PM »
The K2-138 System: A Near-resonant Chain of Five Sub-Neptune Planets Discovered by Citizen Scientists

Yes, this is a very interesting one: the two transits at ~42 days that suggest a sixth planet are consistent with the 3/2 resonance chain ... if you skip two slots at ~18.6 days and 27.9 days

55.8 days, and any multiple thereof, is a whole number multiple of both 18.6 and 27.9. So, perhaps there's something larger with such an orbital period, but not a multiple of ~42 days, that disrupted the formation of any planets at those two slots? If the orbital period is long enough it might not have transited during the observation run.

Offline Star One

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Re: Astronomy Thread
« Reply #311 on: 01/16/2018 07:33 PM »
Ingredients for life revealed in meteorites that fell to Earth

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Two wayward space rocks, which separately crashed to Earth in 1998 after circulating in our solar system’s asteroid belt for billions of years, share something else in common: the ingredients for life. They are the first meteorites found to contain both liquid water and a mix of complex organic compounds such as hydrocarbons and amino acids.

A detailed study of the chemical makeup within tiny blue and purple salt crystals sampled from these meteorites, which included results from X-ray experiments at the Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab), also found evidence for the pair’s past intermingling and likely parents. These include Ceres, a brown dwarf planet that is the largest object in the asteroid belt, and the asteroid Hebe, a major source of meteorites that fall on Earth.

https://astronomynow.com/2018/01/16/ingredients-for-life-revealed-in-meteorites-that-fell-to-earth/

Online jgoldader

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Re: Astronomy Thread
« Reply #312 on: 01/16/2018 08:36 PM »
Ingredients for life revealed in meteorites that fell to Earth

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Two wayward space rocks, which separately crashed to Earth in 1998 after circulating in our solar system’s asteroid belt for billions of years, share something else in common: the ingredients for life. They are the first meteorites found to contain both liquid water and a mix of complex organic compounds such as hydrocarbons and amino acids.

A detailed study of the chemical makeup within tiny blue and purple salt crystals sampled from these meteorites, which included results from X-ray experiments at the Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab), also found evidence for the pair’s past intermingling and likely parents. These include Ceres, a brown dwarf planet that is the largest object in the asteroid belt, and the asteroid Hebe, a major source of meteorites that fall on Earth.

https://astronomynow.com/2018/01/16/ingredients-for-life-revealed-in-meteorites-that-fell-to-earth/

I'm pretty sure I remember a while back reading about water from the ancient Earth discovered in salt crystals from fossilized rocks... ah, here it is!

https://www.sciencedaily.com/releases/2001/12/011210163624.htm

This new study looks to be in a similar spirit.  (Boy, it really WAS a while back!)  Awfully interesting stuff.
« Last Edit: 01/16/2018 08:37 PM by jgoldader »
Recovering astronomer

Offline Star One

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Re: Astronomy Thread
« Reply #313 on: 01/17/2018 08:11 PM »
The Third Workshop on Extremely Precise Radial Velocities: The New Instruments

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The Third Workshop on Extremely Precise Radial Velocities was held at the Penn Stater Conference Center and Hotel in State College, Pennsylvania, USA from 2016 August 14 to 17, and featured over 120 registrants from around the world. Here we provide a brief description of the conference, its format, and its session topics and chairs. 23 instrument teams were represented in plenary talks, and we present a table containing the basic characteristics of their new precise Doppler velocimeters.

https://arxiv.org/abs/1801.05383

Offline Star One

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Astronomy Thread
« Reply #314 on: 01/18/2018 07:33 PM »
Using Gravitational-wave Observations and Quasi-universal Relations to Constrain the Maximum Mass of Neutron Stars

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Combining the GW observations of merging systems of binary neutron stars and quasi-universal relations, we set constraints on the maximum mass that can be attained by nonrotating stellar models of neutron stars. More specifically, exploiting the recent observation of the GW event GW170817 and drawing from basic arguments on kilonova modeling of GRB 170817A together with the quasi-universal relation between the maximum mass of nonrotating stellar models ${M}_{\mathrm{TOV}}$ and the maximum mass supported through uniform rotation ${M}_{\max }\,=({1.20}_{-0.05}^{+0.02}){M}_{\mathrm{TOV}}$, we set limits for the maximum mass to be ${2.01}_{-0.04}^{+0.04}\leqslant {M}_{\mathrm{TOV}}/{M}_{\odot }\lesssim {2.16}_{-0.15}^{+0.17}$, where the lower limit in this range comes from pulsar observations. Our estimate, which follows a very simple line of arguments and does not rely on the modeling of the electromagnetic signal in terms of numerical simulations, can be further refined as new detections become available. We briefly discuss the impact that our conclusions have on the equation of state of nuclear matter.

http://iopscience.iop.org/article/10.3847/2041-8213/aaa401/meta

New Titan Findings from Topographical Map

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Cassini’s huge dataset will yield discoveries for many years, as witness the global topographical map of Titan that has been assembled by Cornell University astronomers. The map draws on topographical data of the moon from multiple sources by way of studying its terrain and the flow of its surface liquids. Bear in mind that only 9 percent of Titan has been observed at relatively high resolution, and another 25-30 percent at lower resolution. For the remainder, the team mapped the surface using an interpolation algorithm and a global minimization process described in the first of two papers in Geophysical Review Letters.

https://www.centauri-dreams.org/?p=39157
« Last Edit: 01/18/2018 07:46 PM by Star One »

Offline jebbo

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Re: Astronomy Thread
« Reply #315 on: 01/19/2018 07:57 AM »
Interesting proposal for a large space-based telescope to hunt for biosignatures ... this is the first ESA L4 idea I've seen (might be premature to create an ESA L4 mission competition thread ;) )

Personally, in that time frame, I'd be thinking about on-orbit assembly rather than single fairing-limited launch.

SUPERSHARP - Segmented Unfolding Primary for Exoplanet Research via Spectroscopic High Angular Resolution Photography

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We propose to search for biosignatures in the spectra of reflected light from about 100 Earth-sized planets that are already known to be orbiting in their habitable zones (HZ). For a sample of G and K type hosts, most of these planets will be between 25 and 50 milli-arcsec (mas) from their host star and 1 billion to 10 billion times fainter. To separate the planet's image from that of its host star at the wavelength (763nm) of the oxygen biosignature we need a telescope with an aperture of 16 metres. Furthermore, the intensity of the light from the host star at the position in the image of the exoplanet must be suppressed otherwise the exoplanet will be lost in the glare.
This presents huge technical challenges. The Earth's atmosphere is turbulent which makes it impossible to achieve the required contrast from the ground at 763nm. The telescope therefore needs to be in space and to fit the telescope in the rocket fairing it must be a factor of 4 or more times smaller when folded than when operational. To obtain spectroscopy of the planet's biosignature at 763nm we need to use an integral field spectrometer (IFS) with a field of view (FOV) of 1000 x 1000 milli-arcsec (mas) and a spectral resolution of 100. This is a device that simultaneously takes many pictures of the exoplanet each at a slightly different wavelength which are then recorded as a data cube with two spatial dimensions and one wavelength dimension. In every data cube wavelength slice, the background light from the host star at the location of the planet image must be minimised. This is achieved via a coronagraph which blocks the light from the host star and active/adaptive optics techniques which continuously maintain very high accuracy optical alignment to make the images as sharp as possible. These are the technical challenges to be addressed in a design study.

https://arxiv.org/abs/1801.06111

--- Tony
« Last Edit: 01/19/2018 07:57 AM by jebbo »

Offline Star One

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Re: Astronomy Thread
« Reply #316 on: 01/19/2018 08:48 PM »

Offline Star One

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Astronomy Thread
« Reply #317 on: 01/23/2018 08:06 PM »
Evidence of an Upper Bound on the Masses of Planets and Its Implications for Giant Planet Formation

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Celestial bodies with a mass of $M\approx 10\,{M}_{\mathrm{Jup}}$ have been found orbiting nearby stars. It is unknown whether these objects formed like gas-giant planets through core accretion or like stars through gravitational instability. I show that objects with $M\lesssim 4\,{M}_{\mathrm{Jup}}$ orbit metal-rich solar-type dwarf stars, a property associated with core accretion. Objects with $M\gtrsim 10\,{M}_{\mathrm{Jup}}$ do not share this property. This transition is coincident with a minimum in the occurrence rate of such objects, suggesting that the maximum mass of a celestial body formed through core accretion like a planet is less than $10\,{M}_{\mathrm{Jup}}$. Consequently, objects with $M\gtrsim 10\,{M}_{\mathrm{Jup}}$ orbiting solar-type dwarf stars likely formed through gravitational instability and should not be thought of as planets. Theoretical models of giant planet formation in scaled minimum-mass solar nebula Shakura–Sunyaev disks with standard parameters tuned to produce giant planets predict a maximum mass nearly an order of magnitude larger. To prevent newly formed giant planets from growing larger than $10\,{M}_{\mathrm{Jup}}$, protoplanetary disks must therefore be significantly less viscous or of lower mass than typically assumed during the runaway gas accretion stage of giant planet formation. Either effect would act to slow the Type I/II migration of planetary embryos/giant planets and promote their survival. These inferences are insensitive to the host star mass, planet formation location, or characteristic disk dissipation time.

http://iopscience.iop.org/article/10.3847/1538-4357/aa961c

Medium-sized satellites of large Kuiper belt objects

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While satellites of mid- to small-Kuiper belt objects tend to be similar in size and brightness to their primaries, the largest Kuiper belt objects preferentially have satellites with small fractional brightness. In the two cases where the sizes and albedos of the small faint satellites have been measured, these satellites are seen to be small icy fragments consistent with collisional formation. Here we examine Dysnomia and Vanth, the satellites of Eris and Orcus, respectively. Using the Atacama Large Millimeter Array, we obtain the first spatially resolved observations of these systems at thermal wavelengths. We find a diameter for Dysnomia of 700±115 km and for Vanth of 475+/-75 km, with albedos of 0.04_+0.02_-0.01 and 0.08+/-0.02 respectively. Both Dysnomia and Vanth are indistinguishable from typical Kuiper belt objects of their size. Potential implications for the formation of these types of satellites are discussed.

https://arxiv.org/abs/1801.07221
« Last Edit: 01/23/2018 08:22 PM by Star One »

Offline Star One

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Re: Astronomy Thread
« Reply #318 on: 01/24/2018 04:51 PM »
Really like Phil Plait’s writing on this article, he has a really good way of getting things across.

THE STAR HD 4113 IS WAY, *WAY* MORE THAN MEETS THE EYE

http://www.syfy.com/syfywire/the-star-hd-4113-is-way-way-more-than-meets-the-eye

Offline jebbo

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Re: Astronomy Thread
« Reply #319 on: 01/24/2018 05:00 PM »
Lol, I'm not a huge fan of his style .. all the gosh wow stuff irritates me. But he does explain things well.

Edit: though I must say HD 4113 deserves the odd gosh, wow ;-)

--- Tony
« Last Edit: 01/24/2018 05:01 PM by jebbo »