Author Topic: Astronomy Thread  (Read 96731 times)

Offline RotoSequence

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Re: Astronomy Thread
« Reply #540 on: 08/22/2018 06:03 AM »
Which if you had read the article you would have seen pointed out.

And reading the article makes the critique offered seem even less notable than I'd initially thought. Who hasn't gotten into a debate with Sean Carroll at this point?  ;)

Offline Star One

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Re: Astronomy Thread
« Reply #541 on: 08/22/2018 06:56 AM »
Eerie Sky Glow Called 'Steve' Isn't an Aurora, Is 'Completely Unknown' to Science

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Given its coincidence with the northern lights, Steve was just thought to be part of the aurora — the shimmering sheets of nighttime color that appear in the sky when charged plasma particles streak out of the sun, sail across space on solar winds and jolt down Earth's magnetic field toward the planet's poles. However, a new study published today (Aug. 20) in the journal Geophysical Research Letters suggests that such a simple explanation might not apply.

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For their new study, the team combined images taken by a network of ground-based cameras with data collected from one of the National Oceanic and Atmospheric Administration's Polar-orbiting Operational Environmental Satellites, which were equipped with instruments capable of detecting charged particles descending through Earth's atmosphere.

Contrary to the findings from the Steve study published earlier this year, the satellite did not detect any charged particles raining down toward Earth's magnetic-field lines, indicating that whatever created Steve did not follow the same rules as the solar particles that create the aurora.

https://www.livescience.com/63385-steve-not-aurora-mystery-phenomenon.html


Offline Star One

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Re: Astronomy Thread
« Reply #542 on: 08/22/2018 08:24 PM »
Stars memorize rebirth of our home galaxy

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The Milky Way galaxy has died once before, and we are now in what is considered its second life. Calculations by Masafumi Noguchi (Tohoku University) have revealed previously unknown details about the Milky Way. These were published in the July 26 edition of Nature.

https://phys.org/news/2018-08-stars-rebirth-home-galaxy

Offline dougkeenan

Re: Astronomy Thread
« Reply #543 on: 08/23/2018 06:49 PM »

Offline Star One

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Astronomy Thread
« Reply #544 on: 08/28/2018 08:01 PM »
Eclipsing binaries in the open cluster Ruprecht 147. I: EPIC 219394517

Eclipsing binaries in star clusters offer more stringent tests of stellar evolution theory than field binaries because models must not only match the binary properties, but also the radiative properties of all other cluster members at a single chemical composition and a single age. Here we report new spectroscopic observations of the G type, detached eclipsing binary EPIC 219394517 in the open cluster Ruprecht 147 ([Fe/H] = +0.10), which was observed in late 2015 by the K2 mission. A joint analysis of our radial-velocity measurements and the K2 light curve shows the 6.5 day orbit to be very nearly circular. We derive highly precise masses of 1.0782 +/- 0.0019 Msun and 1.0661 (+0.0027/-0.0021) Msun, radii of 1.055 +/- 0.011 Rsun and 1.042 +/- 0.012 Rsun, and effective temperatures of 5930 +/- 100 K and 5880 +/- 100 K for the primary and secondary, respectively. The distance we infer, 283 (+18/-16) pc, corresponds to a parallax in good agreement with the Gaia/DR2 value for the star. Current stellar evolution models from the MIST and PARSEC series match the above physical properties very well at ages of 2.48 and 2.65 Gyr. Isochrones for these same ages and the measured composition, along with our reddening estimate for EPIC 219394517, also show generally good agreement with the optical and near-infrared color-magnitude diagrams of the cluster, which can be constructed with no free parameters as the distances of all member stars are known from Gaia.

https://arxiv.org/abs/1808.07482

Meteorite data indicate Jupiter underwent distinct growth phases

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Analysis of meteorite data indicates the growth of Jupiter into the solar system’s most massive planet was held up for about two million years during a phase in which kilometre-size planetesimals crashed into it, releasing heat that prevented rapid cooling, contraction and further gas accretion.

https://astronomynow.com/2018/08/27/meteorite-data-indicate-jupiter-underwent-distinct-growth-phases/

« Last Edit: 08/28/2018 08:09 PM by Star One »

Offline Star One

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Re: Astronomy Thread
« Reply #545 on: 08/30/2018 08:11 PM »
Unstoppable Monster in the Early Universe - ALMA obtains most detailed view of distant starburst galaxy

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Astronomers obtained the most detailed anatomy chart of a monster galaxy located 12.4 billion light-years away. Using the Atacama Large Millimeter/submillimeter Array (ALMA), the team revealed that the molecular clouds in the galaxy are highly unstable, which leads to runaway star formation. Monster galaxies are thought to be the ancestors of the huge elliptical galaxies in today’s Universe, therefore these findings pave the way to understand the formation and evolution of such galaxies.

https://alma-telescope.jp/en/news/press/aztecone-201808

Offline Star One

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Re: Astronomy Thread
« Reply #546 on: 09/01/2018 02:16 PM »
Water worlds could support life, study says

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Analysis by UChicago, Penn State scientists challenges idea that life requires ‘Earth clone’

https://news.uchicago.edu/story/water-worlds-could-support-life-study-says

Offline Star One

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Re: Astronomy Thread
« Reply #547 on: 09/03/2018 06:37 AM »
How a NASA scientist looks in the depths of the Great Red Spot to find water on Jupiter

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But one critical question has bedeviled astronomers for generations: Is there water deep in Jupiter's atmosphere, and if so, how much?

Gordon L. Bjoraker, an astrophysicist at NASA's Goddard Space Flight Center in Greenbelt, Maryland, reported in a recent paper in the Astronomical Journal that he and his team have brought the Jovian research community closer to the answer.

https://m.phys.org/news/2018-08-nasa-scientist-depths-great-red.html

Offline Star One

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Re: Astronomy Thread
« Reply #548 on: 09/07/2018 07:48 PM »
Polaris, the North Star
Friday, September 7, 2018
Science Update - A look at CfA discoveries from recent journals
The North Star, Polaris, is a Cepheid variable: one whose mass, age and physical conditions generate periodic oscillations with a period proportional to the star's intrinsic luminosity. This extraordinarily useful property of Cepheid variables, discovered and calibrated at Harvard by Henrietta Leavitt starting in 1908, allows them to be used as cosmic distance calibrators. By comparing the intrinsic brightness as determined from the period (which is easily measured) with the measured brightness, the period-luminosity relationship, a precise distance can in principle be obtained. Cepheids in nearby galaxies that are receding from us provide the basis for the famous distance-velocity relationship of galaxies that underpins the expanding model of the universe (the "big bang" model). Cepheids are so important that they have also become benchmarks for testing our understanding of stellar evolution.

Polaris is not only famous as the beacon for early navigators, it is also the closest Cepheid to earth (445.5 light-years away), and a subject of intense study. It is a member of a triple system, and one source of confusion about its development has been the extent to which its companion stars could have affected its evolution. The star we can see by eye, Polaris Aa, has a close companion, Polaris Ab that orbits it in 29.59 years; a third star, Polaris B, orbits these two but is one hundred times farther away. Two more stars nearby, Polaris C and D, might also be faint companions.

Three CfA astronomers, Nancy Remage Evans, Margarita Karovska, and Evan Tingle led a team that has been monitoring Polaris with the Hubble Space Telescope since 2005. In their images they are able to resolve the two stars Aa and Ab and to follow their apparent separation which varies during the orbit; the most recent separation of these two in their mutual elliptical orbit is only about twelve astronomical units (about the distance of Saturn from the Sun). They have now incorporated into their results the newly released data from the Gaia mission, a spacecraft that has been measuring with new precision the distances to over a billion stars. The distance to Polaris (the above-mentioned value is from Gaia) settles a long-standing uncertainty about the distance which earlier authors found to be between about 326 light-years to 522 light-years. The newly reliable distance also fixes the intrinsic luminosity and thus enables a more careful calibration of Polaris’ period-luminosity relationship.

The situation is not what astronomers had previously thought. Polaris has a significantly lower mass (3.45 solar-masses, with an uncertainty of about 22%) than was predicted by conventional Cepheid models (one value was close to seven solar-masses). There is also evidence that Polaris Aa has undergone some mass loss, that its age is slightly older than expected from the models, and (not least) that the evolution may have been very complicated indeed with the triple system resulting from a prior merger event. While these critical issues do not dramatically alter the general conclusions about Cepheid stars, they do show that further refinements to our understanding of Cepheids will be vital to a more accurate and unambiguous period-luminosity relationship; tracking the orbit longer will help.

Offline Star One

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Re: Astronomy Thread
« Reply #549 on: 09/10/2018 08:32 PM »
The Sands of Phobos: The Martian moon's eccentric orbit refreshes its surface

Ronald-Louis Ballouz, Nicola Baresi, Sarah T. Crites, Yasuhiro Kawakatsu, Masaki Fujimoto
(Submitted on 7 Sep 2018)
The surface of the Martian moon Phobos exhibits two distinct geologic units, known as the red and blue units. The provenance of these regions is uncertain yet crucial to understanding the origin of the Martian moon and its interaction with the space environment. Here we show that Phobos' orbital eccentricity can cause sufficient grain motion to refresh its surface, suggesting that space weathering is the likely driver of the dichotomy on the moon's surface. In particular, we predict that blue regions are made up of pristine endogenic material that can be uncovered in steep terrain subject to large variations in the tidal forcing from Mars. The predictions of our model are consistent with current spacecraft observations which show that blue units are found near these regions.

https://arxiv.org/abs/1809.02520

Offline Star One

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Re: Astronomy Thread
« Reply #550 on: 09/10/2018 08:50 PM »
Artificial intelligence helps track down mysterious cosmic radio bursts

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While most fast radio bursts are one-offs, the source here, FRB 121102, is unique in emitting repeated bursts. This behavior has drawn the attention of many astronomers hoping to pin down the cause and the extreme physics involved in fast radio bursts.

The AI algorithms dredged up the radio signals from data were recorded over a five-hour period on Aug. 26, 2017, by the Green Bank Telescope in West Virginia. An earlier analysis of the 400 terabytes of data employed standard computer algorithms to identify 21 bursts during that period. All were seen within one hour, suggesting that the source alternates between periods of quiescence and frenzied activity, said Berkeley SETI postdoctoral researcher Vishal Gajjar.

UC Berkeley Ph.D. student Gerry Zhang and collaborators subsequently developed a new, powerful machine-learning algorithm and reanalyzed the 2017 data, finding an additional 72 bursts not detected originally. This brings the total number of detected bursts from FRB 121102 to around 300 since it was discovered in 2012.

https://m.phys.org/news/2018-09-artificial-intelligence-track-mysterious-cosmic.html


Offline Star One

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Re: Astronomy Thread
« Reply #551 on: 09/12/2018 08:37 PM »
Medium-sized satellites of large Kuiper belt objects

Michael E. Brown, Bryan J. Butler
(Submitted on 22 Jan 2018 (v1), last revised 10 Sep 2018 (this version, v2))
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


Offline Star One

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Astronomy Thread
« Reply #552 on: 09/12/2018 08:57 PM »
A Galactic Gem

ESO’s FORS2 instrument captures stunning details of spiral galaxy NGC 3981

This wonderful image shows the resplendent spiral galaxy NGC 3981 suspended in the inky blackness of space. This galaxy, which lies in the constellation of Crater (the Cup), was imaged in May 2018 using the FOcal Reducer and low dispersion Spectrograph 2 (FORS2) instrument on ESO’s Very Large Telescope (VLT).

FORS2 is mounted on Unit Telescope 1 (Antu) of the VLT at ESO’s Paranal Observatory in Chile. Amongst the host of cutting-edge instruments mounted on the four Unit Telescopes of the VLT, FORS2 stands apart due to its extreme versatility. This ”Swiss Army knife” of an instrument is able to study a variety of astronomical objects in many different ways — as well as being capable of producing beautiful images like this one.

The sensitive gaze of FORS2 revealed NGC 3981’s spiral arms, strewn with vast streams of dust and star-forming regions, and a prominent disc of hot young stars. The galaxy is inclined towards Earth, allowing astronomers to peer right into the heart of this galaxy and observe its bright centre, a highly energetic region containing a supermassive black hole. Also shown is NGC 3981’s outlying spiral structure, some of which appears to have been stretched outwards from the galaxy, presumably due to the gravitational influence of a past galactic encounter.

NGC 3981 certainly has many galactic neighbours. Lying approximately 65 million light years from Earth, the galaxy is part of the NGC 4038 group, which also contains the well-known interacting Antennae Galaxies. This group is part of the larger Crater Cloud, which is itself a smaller component of the Virgo Supercluster, the titanic collection of galaxies that hosts our own Milky Way galaxy.

NGC 3981 is not the only interesting feature captured in this image. As well as several foreground stars from our own galaxy, the Milky Way, FORS2 also captured a rogue asteroid streaking across the sky, visible as the faint line towards the top of the image. This particular asteroid has unwittingly illustrated the process used to create astronomical images, with the three different exposures making up this image displayed in the blue, green and red sections of the asteroid’s path.

This image was taken as part of ESO’s Cosmic Gems programme, an outreach initiative to produce images of interesting, intriguing or visually attractive objects using ESO telescopes, for the purposes of education and public outreach. The programme makes use of telescope time that cannot be used for science observations. In case the data collected could be useful for future scientific purposes, these observations are saved and made available to astronomers through ESO’s science archive.

https://www.eso.org/public/news/eso1830/



« Last Edit: 09/12/2018 09:01 PM by Star One »

Offline CuddlyRocket

Re: Astronomy Thread
« Reply #553 on: 09/17/2018 06:15 AM »
The hot Jupiter period-mass distribution as a signature of in situ formation (Bailey & Batygin) (arXiv)

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(Abstract)
More than two decades after the widespread detection of Jovian-class planets on short-period orbits around other stars, their dynamical origins remain imperfectly understood. In the traditional narrative, these highly irradiated giant planets, like Jupiter and Saturn, are envisioned to have formed at large stello-centric distances and to have subsequently undergone large-scale orbital decay. Conversely, more recent models propose that a large fraction of hot Jupiters could have formed via rapid gas accretion in their current orbital neighborhood. In this study, we examine the period-mass distribution of close-in giant planets, and demonstrate that the inner boundary of this population conforms to the expectations of the in-situ formation scenario. Specifically, we show that if conglomeration unfolds close to the disk's inner edge, the semi-major axis - mass relation of the emergent planets should follow a power law a∝M−2/7 - a trend clearly reflected in the data. We further discuss corrections to this relationship due to tidal decay of planetary orbits. Although our findings do not discount orbital migration as an active physical process, they suggest that the characteristic range of orbital migration experienced by giant planets is limited.

Despite the title and abstract, the paper seems to consider the sem-major axis - mass distribution!? Seems an odd mistake to make.

I like the fact that hot-Jupiter formation by migration is described as "the traditional narrative"! :) It's only been ~25 years since the first was discovered - just shows how fast this field has been moving.

Offline Star One

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« Last Edit: 09/19/2018 07:48 PM by Star One »

Offline Star One

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Re: Astronomy Thread
« Reply #555 on: 09/24/2018 01:04 PM »
Planet-Planet Tides in the TRAPPIST-1 System

Jason T. Wright
(Submitted on 21 Sep 2018)
The star TRAPPIST-1 hosts a system of seven transiting, terrestrial exoplanets apparently in a resonant chain, at least some of which are in or near the Habitable Zone. Many have examined the roles of tides in this system, as tidal dissipation of the orbital energy of the planets may be relevant to both the rotational and orbital dynamics of the planets, as well as their habitability. Generally, tides are calculated as being due to the tides raised on the planets by the star, and tides raised on the star by the planets. I write this research note to point out a tidal effect that may be at least as important as the others in the TRAPPIST-1 system and which is so far unremarked upon in the literature: planet-planet tides. Under some reasonable assumptions, I find that for every planet p in the TRAPPIST-1 system there exists some other planet q for which the planet-planet dynamical tidal strain is within an order of magnitude of the stellar eccentricity tidal strain, and that the effects of planet f on planet g are in fact greater than that of the star on planet g. It is thus not obvious that planet-planet tides can be neglected in the TRAPPIST-1 exoplanetary system, especially the tides on planet g due to planet f, if the planets are in synchronous rotation.
Comments:3 pp Research Note of the AAS
Subjects:Earth and Planetary Astrophysics (astro-ph.EP)
Journal reference:Wright (2018) Res. Notes AAS, 2, 175
DOI:10.3847/2515-5172/aae260
Cite as:arXiv:1809.08166 [astro-ph.EP]
 (or arXiv:1809.08166v1 [astro-ph.EP] for this version)

https://arxiv.org/abs/1809.08166

Offline Star One

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Re: Astronomy Thread
« Reply #556 on: 09/26/2018 03:53 PM »
BETA PIC B: AN EXOPLANET EMERGES FROM THE GLARE

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Subsequent observations taken over the years showed something incredible: The actual motion of the planet as it orbited the star! Images taken in 2009 and 2010 showed that it had moved from one side of the star to the other: Clear evidence of orbital motion. We happen to see its orbit almost (but not exactly) edge-on, so we see it move back and forth over the period orbit.

In the following years the planet made it ‘round the bend, and started heading back toward conjunction (closest approach) with Beta Pic, which happened in late September 2017. After that it was too close to the star to see, lost in the glare.

But now it has re-emerged, and was captured in an image yet again by the Spectro-Polarimetric High-contrast Exoplanet REsearch (or just SPHERE) detector on the ginormous 8.2-meter Very Large Telescope in Chile. This was taken just days ago, on September 17, 2018, and clearly shows the planet:

https://www.syfy.com/syfywire/beta-pic-b-an-exoplanet-emerges-from-the-glare

Offline Alpha_Centauri

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Re: Astronomy Thread
« Reply #557 on: 09/28/2018 08:10 AM »
Sort of astronomy but also maybe (...or maybe not) big news for particle physics.

A new preprint has been posted claiming that a set of cosmic ray events from a balloon-borne experiment cannot be explained by the Standard Model and instead propose they come from a low-mass supersymmetric particle.  Should be noted the balloon experiment team themselves are quite cautious about the earth-tunnelling interpretation despite having previously suggested it.

https://www.sciencemag.org/news/2018/09/oddball-particles-tunneling-through-earth-could-point-new-physics
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Oddball particles tunneling through Earth could point to new physics
Twice in the past 13 years, particles from outer space tunneled through Earth and up into the atmosphere above Antarctica, triggering faint pulses of radio waves that were picked up by a balloon-borne detector 35 kilometers above the ice cap. Those two events poke a hole in physicists’ standard model of fundamental particles and forces, and point to the existence of new particles, a team of astrophysicists argues in a new study.

https://www.livescience.com/63692-standard-model-broken-supersymmetry-new-physics.html
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Bizarre Particles Keep Flying Out of Antarctica's Ice, and They Might Shatter Modern Physics

There's something mysterious coming up from the frozen ground in Antarctica, and it could break physics as we know it.

Physicists don't know what it is exactly. But they do know it's some sort of cosmic ray — a high-energy particle that's blasted its way through space, into the Earth, and back out again. But the particles physicists know about — the collection of particles that make up what scientists call the Standard Model (SM) of particle physics — shouldn't be able to do that. Sure, there are low-energy neutrinos that can pierce through miles upon miles of rock unaffected. But high-energy neutrinos, as well as other high-energy particles, have "large cross-sections." That means that they'll almost always crash into something soon after zipping into the Earth and never make it out the other side.

The ANITA Anomalous Events as Signatures of a Beyond Standard Model Particle, and Supporting Observations from IceCube
https://arxiv.org/abs/1809.09615
« Last Edit: 09/28/2018 08:23 AM by Alpha_Centauri »

Offline Star One

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Re: Astronomy Thread
« Reply #558 on: 09/28/2018 03:05 PM »
And I always thought super-symmetry would turn out to be load of hogs wash, but it seems possibly not.

Offline Star One

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Astronomy Thread
« Reply #559 on: 10/01/2018 07:33 AM »
Surprised to see Martin Rees raising this sort of stuff in his book, mind you it maybe he’s a victim of selective quoting with this article.

Earth Could Be Crushed to The Size of a Soccer Field by Particle Accelerator Experiments, Astronomer Warns
« Last Edit: 10/01/2018 07:37 AM by Star One »