astrobites 2017

Find out the latest thinking about our universe.
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A Binary Companion to a Be Star

Postby bystander » Mon Feb 06, 2017 7:24 pm

A Binary Companion to a Be Star
astrobites | 2017 Feb 06
Matthew Green wrote:
What happens if a star spins so fast it throws off its own atmosphere?

We believe this is what we see in a class of stars called Be stars. Be stars are stars of spectral class B whose spectra also show emission lines, often double-peaked ... This shape of emission line can be matched by a model in which the star is surrounded by a disc of material, with the emission coming from the disc rather than the star itself. One side of the disc is moving towards us relative to the star, and its emission is therefore Doppler shifted towards the blue end of the spectrum (‘blue-shifted’). The other side is moving away from us relative to the star, causing its light to be red-shifted. The result is that see two peaks with different wavelengths, each peak corresponding to one side of the disc. ...

A Spectroscopic Orbit for the late-type Be star β CMi - Nick Dulaney et al
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The Largest, Ugliest Duckling in the Universe

Postby bystander » Thu Feb 09, 2017 9:28 pm

The Largest, Ugliest Duckling in the Universe
astrobites | 2017 Feb 07
Zephyr Penoyre wrote:
The night sky is full of fantastically beautiful things.

There are huge rings of ice, pluming jets of ultra-relativistic gas, and (at a rough estimate) at least 14 balloons from children’s birthday parties. Each of these intrigues and excites us with its appearance alone; how did they come to be and what fate ultimately will befall them?

There are also quite a few boring, ugly things up there. And the structure and history of those can be just as enthralling. In this case, I believe, even more so.

We’re going to tell one of those ugly duckling stories. Except in this one we’re going to start off with a bunch of beautiful swans, crash ’em all into each other and end up with one huge, fat and sluggish duckling. ...

The ATLAS3D project - XXV: Two-dimensional kinematic analysis of simulated
galaxies and the cosmological origin of fast and slow rotators
- T. Naab et al
    Monthly Notices of the RAS 444(4):3357 (11 Nov 2014) DOI: 10.1093/mnras/stt1919
    arXiv.org > astro-ph > arXiv:1311.0284 > 01 Nov 2013 (v1), 05 Nov 2013 (v2)
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Can You Tell a Sibling from a Doppelganger?

Postby bystander » Thu Feb 09, 2017 9:33 pm

Can You Tell a Sibling from a Doppelganger?
astrobites | 2017 Feb 08
Ingrid Pelisoli wrote:
Stars are not born alone. Stellar formation occurs inside giant molecular clouds, which collapse when the internal gas pressure cannot overcome gravity. This is known as Jeans instability. The increase in density caused by the collapse leads to a fragmentation of the cloud, forming thus not only one, but many stars from the same original material. Consequently stars that are born together have the same initial composition. In addiction, these sibling stars are subjected to each others’ gravitational pull, so the formation process usually results in a stellar cluster rather than isolated stars. ...

Galactic Doppelganger: The chemical similarity among field stars
and among stars with a common birth origin
- M. Ness et al
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NIKA2: A New Era for Cluster Cosmology

Postby bystander » Thu Feb 09, 2017 9:40 pm

NIKA2: A New Era for Cluster Cosmology
astrobites | 2017 Feb 09
Amber Hornsby wrote:
Residing at the 30m IRAM telescope in Pico Veleta, Spain, the eagerly anticipated New-IRAM-KIDs-array 2 (NIKA2) imaging camera is coming to the end of its commissioning phase and is almost ready to be let loose on the scientific community. Today we will be exploring the capabilities of it and its predecessor NIKA within the field of Cosmology, specifically the Sunyaev-Zel’dovich effect (SZ effect). ...

High Angular Resolution SZ Observations with NIKA and NIKA2 - B. Comis et al
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Don’t Blame Asteroids for the Late Heavy Bombardment!

Postby bystander » Sun Feb 12, 2017 4:04 pm

Don’t Blame Asteroids for the Late Heavy Bombardment!
astrobites | 2017 Feb 10
Michael Hammer wrote:
Asteroids have a bad reputation. They may have wiped out the dinosaurs, and they have threatened the survival of humanity in many terrible movies.

Until today’s featured paper, asteroids were also blamed for the Late Heavy Bombardment (LHB, for short) – a period of time in the early solar system when the Moon, the Earth, and the other rocky planets were hit with an unusually high amount of impactors from a variety of material in space. It lasted from the Sun’s formation 4.6 billion years (Gyr) ago until the impact that created the Orientale crater on the Moon 800 million years later (3.8 Gyr ago). Planetary scientists working on the Apollo missions in the 1960s first hypothesized the LHB when astronauts brought back impact melt rocks from various craters that unexpectedly all dated back to this time. The idea was later extended to include the rest of the inner solar system when planetary scientists found similar cratering histories on each of the rocky planets. These LHB-era impacts are believed to have been caused by some combination of asteroids (from the asteroid belt), comets (from the Kuiper Belt and beyond), and leftover material from the formation of the inner rocky planets. However, it is still not clear which of these three sources was the main culprit.

To address one part of this issue, Nesvorny et al. – the authors of today’s paper, ask: Were there enough impacting asteroids to account for all of the craters on the Moon from the Late Heavy Bombardment? ...

Modeling the Historical Flux of Planetary Impactors - David Nesvorny, Fernando Roig, William F. Bottke
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Galaxies Playing Possum

Postby bystander » Thu Feb 16, 2017 4:52 pm

Galaxies Playing Possum
astrobites | 2017 Feb 13
Paddy Alton wrote:
Early-type galaxies: much-maligned, misnamed, and misunderstood. Maligned for being boring (including by me), misnamed by tradition (the old idea was that formless elliptical blobs settle down into ‘late-type’ spirals: more-or-less the opposite of the truth), but misunderstood? I’ll explain.

You see, early-type galaxies (ETGs) encompass a wide range of galaxy types, from elliptical to lenticular, which all appear to have one thing in common: they’re dead as a doornail. At least, that is, in the sense that they are no longer forming any stars. A galaxy is essentially a really big collection of stars held together by gravity: thus, a galaxy that isn’t forming stars is ultimately doomed. Those stars will eventually die, and then what you have isn’t really a galaxy anymore, but rather just a collection of burnt-out cinders. But are all ETGs really like this? Or are some of them not quite as dead as they might first appear? ...

Investigating early-type galaxy evolution with a multiwavelength approach.
II. The UV structure of 11 galaxies with Swift-UVOT
- R. Rampazzo et al
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Rings of Dust

Postby bystander » Thu Feb 16, 2017 5:03 pm

Rings of Dust
astrobites | 2017 Feb 14
Elisabeth Matthews wrote:
Let’s talk about dust. Again.

Yeah, I know I might be sounding a bit repetitive… but this particular dust is really pretty. Take a look at Figure 1 to see what I mean.

This is data from the SPHERE instrument on the Very Large Telescope. SPHERE is a state-of-the-art high contrast imager, meaning that it is very very good at imaging very very faint things near very very bright nearby stars. This is useful if you want to image exoplanets orbiting those very very bright nearby stars, or image other structures – such as these faint dust rings around the star. ...

SPHERE/SHINE reveals concentric rings in the debris disk of HIP 73145 - M. Feldt et al
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Honey, I found Isolated Dwarfs!

Postby bystander » Thu Feb 16, 2017 5:27 pm

Honey, I found Isolated Dwarfs!
astrobites | 2017 Feb 15
Bhawna Motwani wrote:
The current favourite model for the evolution of the universe, the Lambda Cold Dark Matter (LCDM) model, supports growth of cosmological structure via consolidation of smaller units. Widely referred to as ‘hierarchical’ assembly, this prescription posits that dark matter haloes as small as the size of our solar system act as the first seedlings that gradually grow up to be galaxies, galaxy groups and galaxy clusters. As a natural consequence of this picture, cosmological simulations predict a huge extant population of satellite structures surrounding the present-day structure at all scales that survived during the latter’s build-up process.

So, where are these satellites; have we seen them? ...

Direct evidence of hierarchical assembly at low masses from isolated dwarf galaxy groups - Sabrina Stierwalt et al
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Neutron Star Mergers May Help Short GRBs Go “Boom”

Postby bystander » Thu Feb 16, 2017 5:36 pm

Neutron Star Mergers May Help Short GRBs Go “Boom”
astrobites | 2017 Feb 16
Thankful Cromartie wrote:
The LIGO Scientific Collaboration‘s direct detection of gravitational waves (GWs) is the first whisper from an era of so-called “multimessenger astronomy,” of which astronomers have thus far only been able to dream. The ability to probe an astrophysical event in both the electromagnetic spectrum and in gravitational waves would allow for groundbreaking scientific activities, such as unique tests of general relativity (GR) and understanding the interior properties of neutron stars (NSs). Among the transient events able to produce a strong signal simultaneously in GWs and the EM spectrum are black hole-black hole (BH-BH) mergers, NS-BH mergers, and NS-NS mergers. Intriguingly, NS-BH and NS-NS mergers are strongly favored progenitors of gamma-ray bursts (GRBs), making them ideal multimessenger candidates. ...

Binary Neutron Star Mergers: A Jet Engine for Short Gamma-Ray Bursts - Milton Ruiz et al
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Re: Galaxies Playing Possum

Postby Ann » Fri Feb 17, 2017 12:50 am

bystander wrote:Galaxies Playing Possum
astrobites | 2017 Feb 13
Paddy Alton wrote:
Early-type galaxies: much-maligned, misnamed, and misunderstood. Maligned for being boring (including by me), misnamed by tradition (the old idea was that formless elliptical blobs settle down into ‘late-type’ spirals: more-or-less the opposite of the truth), but misunderstood? I’ll explain.

You see, early-type galaxies (ETGs) encompass a wide range of galaxy types, from elliptical to lenticular, which all appear to have one thing in common: they’re dead as a doornail. At least, that is, in the sense that they are no longer forming any stars. A galaxy is essentially a really big collection of stars held together by gravity: thus, a galaxy that isn’t forming stars is ultimately doomed. Those stars will eventually die, and then what you have isn’t really a galaxy anymore, but rather just a collection of burnt-out cinders. But are all ETGs really like this? Or are some of them not quite as dead as they might first appear? ...

Investigating early-type galaxy evolution with a multiwavelength approach.
II. The UV structure of 11 galaxies with Swift-UVOT
- R. Rampazzo et al


How interesting! I checked out NGC 1533, the galaxy that was shown as a prime example of a seemingly red-and-dead galaxy playing possum and forming stars on the sly.

The colors of NGC 1533 are unremarkable, 0.980 (B-V) and 0.490 (U-B). We wouldn't expect low levels of star formation to affect the B-V colors very much at all, but the U-B index might be more sensitive. But a U-B index of 0.490 does not in itself suggest the presence, even at low levels, of ultraviolet-bright young stars.

Maybe the correct conclusion is that low levels of star formation are found in many elliptical and lenticular galaxies.

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Move over Philae, we have a new lander in town

Postby bystander » Fri Feb 17, 2017 11:08 pm

Move over Philae, we have a new lander in town
astrobites | 2017 Feb 17
Amber Hornsby wrote:
Europa is the smallest of the Galilean moons orbiting Jupiter, but it’s potentially one of the most exciting bodies in our diverse Solar System. Why? With oceans of liquid water hiding underneath its icy crust, Europa is an essential target in the search for life beyond our pale blue dot. To uncover the secrets of this mysterious moon we must take one giant leap for aliens everywhere and get to grips with its poorly understood surface.

Today’s bite will be going beyond the extremely cool science goals of a recently proposed Europa lander, and focusing on one big question. How do we successfully land on a moon? ...

Europa Lander Science Definition Team Report

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The Sun In A Distant Mirror

Postby bystander » Fri Feb 24, 2017 5:44 pm

The Sun In A Distant Mirror
astrobites | 2017 Feb 20
Philipp Plewa wrote:
How can we learn what lies beneath the surface of a star? One approach, called asteroseismology, is to study a star’s vibrations to infer its internal structure. The inside structure of the Sun in particular can be studied in great detail, because its vibrations are actually apparent on its surface (Fig. 1, see also: Helioseismology). The visible pattern of surface quivers shows the imprint of global acoustic oscillations, which are caused by resonant waves traveling through the Sun on peculiar paths, probing various depths. The same must be happening in faraway stars, yet due to their distance only the variability of their overall properties can be measured, for instance changes in brightness or temperature, which are however similarly caused by the stars’ intrinsic oscillations.

An impressive instrument that has been built specifically to measure the brightness of stars with extreme precision over time is the Kepler space telescope. Its primary aim is to detect the transits of exoplanets, but its features make it suitable for asteroseismology as well. The authors of today’s paper investigate how Kepler would see a Sun-like star from far away, by pointing it at Neptune. ...

A Distant Mirror: Solar Oscillations Observed on Neptune by the Kepler K2 Mission - P. Gaulme et al

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Preparing for the Temperature Drop at Night

Postby bystander » Fri Feb 24, 2017 5:56 pm

Preparing for the Temperature Drop at Night
astrobites | 2017 Feb 21
Shang-Min Tsai wrote:
There is an old sci-fi movie “The Chronicles of Riddick” setting on a bizarre planet. One scene I still remember depicted the dawn on the planet. As the sun was rising (Yes, somehow not tidally-locked…), the frozen surface from the night suddenly became so boiling hot that it burned anything into ash within seconds. Fortunately, on Earth, the day-night temperature difference is much milder, usually less than 30 °C, because the atmosphere mitigates the temperature and that the Earth rotates fast (like making evenly grilled chicken by spinning).

Hot Jupiters, on the other hand, are extreme worlds. They orbit very close to their host stars (< 0.1 AU) and are locked by the tidal force into synchronous rotation, always having the same side facing their stars. This makes for interesting atmospheric dynamics. In today’s astrobite, we take a look into these exotic worlds. The authors examined what essentially controls the day-night temperature differences and compare their theory to numerical simulations (so called general circulation models or GCM). ...

Atmospheric Circulation of Hot Jupiters: Dayside-Nightside Temperature Differences - Thaddeus D. Komacek, Adam P. Showman
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TRAPPIST-1: Just right?

Postby bystander » Fri Feb 24, 2017 6:14 pm

TRAPPIST-1: Just right?
astrobites | 2017 Feb 22
Elisabeth Matthews wrote:
Back on May 12th, 2016, the discovery of three planets around the star TRAPPIST-1 was announced – in classic imaginative astronomer fashion, the planets were named b, c and d. It was a big deal, leading to a Nature paper, a NASA press release, and some speedy follow-up work taking a look at the atmospheres of b and c. The atmospheric studies confirmed that these two planets don’t host puffy and hydrogen/helium dominated atmospheres. This is notable, as a puffy hydrogen or helium atmosphere would make the planet uninhabitable. Incidentally, these were the first ever Earth-sized planets to have their atmospheres studied.

TRAPPIST-1 is an exciting system as it’s basically right in our astrophysical backyard: extremely close to us, at just 12 parsecs. For reference, even alpha Centauri, the nearest star system to us, is 1.34 parsecs away. Not only does this make the system feel tangible, it also makes follow-up and characterisation work much easier to carry out. ...

Seven temperate terrestrial planets around the nearby ultracool dwarf star TRAPPIST-1 - Michaël Gillon et al

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Do Electric Cosmologists Dream of the EoR?

Postby bystander » Fri Feb 24, 2017 6:28 pm

Do Electric Cosmologists Dream of the EoR?
astrobites | 2017 Feb 23

If you’re worried about the robot uprising or the much closer inevitability of machines usurping us in the workplace, then this probably isn’t the astrobite to improve your outlook on the matter. However, until the point that we have made ourselves obsolete in almost every field imaginable, we can give you some insight into how machine learning is being used to make discoveries in astronomy, cosmology, and astrophysics. ...

Analysing the 21cm signal from the Epoch of Reionization with artificial neural networks - Hayato Shimabukuro, Benoit Semelin
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Searching for Evidence of Dark Matter in Stellar Streams

Postby bystander » Fri Feb 24, 2017 6:52 pm

Searching for Evidence of Dark Matter in Stellar Streams
astrobites | 2017 Feb 24
Nora Shipp wrote:
The Milky Way is surrounded by elusive, invisible dark matter galaxies, and we finally have a way to find them.

Astrophysicists have already discovered dozens of visible satellite galaxies orbiting the Milky Way by picking out clusters of stars from images like Fig. 1. Each of these galaxies has a halo of invisible dark matter that does not emit or reflect light, but they all also have stars at their centers that give away their location. However, we also expect there to be smaller dark matter halos around the Milky Way that aren’t quite big enough to gravitationally pull together clumps of gas at their centers to form stars. These are the invisible Milky Way dark galaxies. ...

A sharper view of Pal 5's tails: Discovery of stream perturbations
with a novel non-parametric technique
- Denis Erkal, Sergey E. Koposov, Vasily Belokurov

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HD 95086 — Constraints and Conundrums

Postby bystander » Fri Mar 03, 2017 4:30 pm

HD 95086 — Constraints and Conundrums
astrobites | 2017 Feb 27
Mara Zimmerman wrote:
HD 95086 is one of the more well studied and characterized systems; it hosts planetary, planetesimal, and dust components, which make it quite the intriguing subject to study. Its planet HD 95086 b was directly imaged by GPI in late 2013; the planet is about 4 times the mass of Jupiter and orbits its star at a distance of about 56 AU. The disk in the system is characterized by three components— a 55 K cool component, a 75 K warm component at – each of those two corresponding to a planetesimal belt– and a possible hot component at 300 K, which could suggest activity in the habitable zone of the star (Su et al. 2015). There is also quite a large gap in HD 95086’s disk, extending from about 8 to 80 AU. This system presents a perfect playground for the study of evolution and formation of unusual systems. ...

Constraints on the Architecture of the HD 95086 Planetary System with the Gemini Planet Imager - Julien Rameau et al

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Rock & Roll & Water

Postby bystander » Fri Mar 03, 2017 4:45 pm

Rock & Roll & Water: A Statistical Look at Water Accretion as a Polluter of White Dwarfs
astrobites | 2017 Feb 28
Jamila Pegues wrote:
Atmospheric pollution… elsewhere in space?!

Astronomers, like astrochemists and astrobiologists, gaze beyond the skies for signs of exoplanets with liquid water, in the hopes of narrowing down the search for life as we know it somewhere out in space. But for some extrasolar systems, as the authors of today’s astrobite show, we may be looking a bit too late.

Today’s authors investigate if water from rocky bodies may be polluting the atmospheres of helium white dwarfs. White dwarfs (aka, WDs) have very high surface gravities. That means that the lightest elements, hydrogen and helium, float at a WD’s surface, while heavier elements, like carbon and oxygen, are dragged down below the surface like crocodiles in quicksand. It takes about a million years for the heavier elements, or metals as astronomers call them, to sink below the surface down to lower atmospheric layers of WDs. That’s a snap of your fingers compared to how it takes billions of years for WDs to cool into black dwarfs. ...

Trace hydrogen in helium atmosphere white dwarfs as a possible signature of water accretion - Nicola Pietro Gentile Fusillo et al
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Peeking Through the Haze

Postby bystander » Fri Mar 03, 2017 4:54 pm

Peeking Through the Haze: A Look at Titan’s Bright Surface Features
astrobites | 2017 Mar 01
Kerrin Hensley wrote:
Titan, Saturn’s largest moon, is the only solar system object other than the Earth to have a thick atmosphere and standing surface liquid. When the Cassini spacecraft began observing Titan, it even discovered lakes and seas dotting the northern hemisphere. Don’t fire up your rocket just yet, though—because Titan is so cold, the lakes and seas are filled with liquid methane and ethane rather than water.

Titan’s thick, methane-rich atmosphere makes it difficult to observe the surface at visible wavelengths. Luckily, there are several windows in the near-infrared through which light can pass and reveal the surface. Seven of these windows overlap with the wavelength range covered by Cassini’s Visual and Infrared Mapping Spectrometer (VIMS). By looking at how the brightness of the surface changes with wavelength, we can learn about the composition of the surface material. ...

Compositional Similarities and Distinctions Between Titan’s Evaporitic Terrains - Shannon MacKenzie, Jason Barnes
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Teaching Stellar Classification to Computers

Postby bystander » Fri Mar 03, 2017 5:01 pm

Teaching Stellar Classification to Computers
astrobites | 2017 Mar 02
Philipp Plewa wrote:
A fundamental property of a star is its effective temperature, which observational astronomers like to express in terms of a spectral type or color. A hot star of class O, for example, emits more light at shorter wavelengths, which makes it bluer than a colder star of class G or M (spectrally speaking). Ideally, the spectral type of a star is determined from a high-resolution spectrum. The next best thing would be to know its brightness in at least a few different wavelengths bands. For a large sample of stars, this method (multi-band photometry) is usually the most efficient. It might seem unintuitive, but the authors of today’s paper show that under certain conditions a star’s spectral type can also be determined accurately from a single-band image only, using supervised machine learning techniques. ...

Stellar classification from single-band imaging using machine learning - T. Kuntzer, M. Tewes, F. Courbin
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Let’s talk about policy, baby

Postby bystander » Fri Mar 03, 2017 5:09 pm

Let’s talk about policy, baby
astrobites | 2017 Mar 03
Mia de los Reyes wrote:
I recently attended a panel workshop held by the Centre for Science and Policy at the University of Cambridge, and I wanted to summarize some of the things I learned in this Astrobite.

I know, I know. “Policy” sounds complicated, and many scientists either don’t want to read about it or feel powerless when dealing with it. But science is done by humans, and policy affects all of us. That means that whether we like it or not, science and policy are inextricably related. ...
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Getting a peek at exozodis

Postby bystander » Fri Mar 10, 2017 4:45 pm

Getting a peek at exozodis
astrobites | 2017 Mar 04
Eckhart Spalding wrote:
The inner solar system contains a wispy, flared disk of dusty residue from comets and asteroid collisions, along with a bit of interstellar dust. This is zodiacal dust, which you can see with your naked eye. Zodiacal disk analogs are also known to exist around other stars and have attracted considerable interest ever since their first discovery in 2006. Known disks are dramatically different from the zodiacal disk, so they must depend on other physical mechanisms. Exozodis could also represent the greatest source of noise for future space-based missions to directly image exo-Earths. Before we ever get a picture of an exo-Earth, we need to advance our understanding of exozodis. ...

Constraints on the structure of hot exozodiacal dust belts - Florian Kirchschlager et al
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A Stellar Way to Identify Planets in Protoplanetary Disks

Postby bystander » Fri Mar 10, 2017 4:54 pm

Bridging the Gap: A Stellar Way to Identify Planets in Protoplanetary Disks
astrobites | 2017 Mar 06
Jamila Pegues wrote:
Ever wanted to witness the Earth’s formation in action?

Well… you may have missed your chance.

Unless you have access to a time machine, Superman’s sketchy ability to go back in time, or any other manner of disobeying the laws of space-time as humans (barely) understand them, there’s no way for you to rewind the clock and witness Earth’s formation when you yourself hadn’t even formed yet (presumably).

That’s one reason some astronomers turn their telescopes beyond the Solar System and peer out at protoplanetary disks. A protoplanetary disk consists of a young star at its center, surrounded by a rotating disk of dust and gas. The Solar System is thought to have once been a protoplanetary disk, before Earth and its other planets formed. So, by observing and modeling the behavior of growing planets in protoplanetary disks out in space, astronomers can piece together the complex process of planet formation – and, by extension, how Earth came to be. ...

Mass Constraint for a Planet in a Protoplanetary Disk from the Gap Width - Kazuhiro D. Kanagawa et al
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Baby Galaxies Blowing Bubbles

Postby bystander » Fri Mar 10, 2017 5:03 pm

Baby Galaxies Blowing Bubbles
astrobites | 2017 Mar 07
Christopher Lovell wrote:
About four hundred thousand years after the Big Bang, the universe settled into a pretty dull period in its history. There were no stars or galaxies, just one massive expanse of neutral hydrogen, sitting in the dark. This period in the universe’s history, known appropriately as the Dark Ages, came abruptly to an end when the first stars were born and began to shine, dumping loads of high energy photons into their surroundings. These photons created ‘bubbles’ of ionised hydrogen around the stars, which slowly grew as more photons were pumped out by the stars. The bubbles surrounding the first stars were pretty small, but later, as stars began to group together into the first galaxies, these bubbles were blown much bigger by the combined photons from all the stars in the galaxy. Over time the bubbles from neighbouring galaxies began to overlap, until eventually all of the hydrogen in the universe was ionised (see Figure 1). This process is known as reionisation (Astrobites has written plenty about reionisation in the past – for more background, go check out some of these articles), and it’s a key period in the universe’s history.

The subject of today’s bite are these ionised bubbles, the baby galaxies that blew them, and how much they contributed to reionisation. We will see that there is a close relationship between the properties of a galaxy and the size of the bubble it can blow. The size of the bubble also affects how easily we can see the galaxy. Finally, we’ll also learn about two upcoming observatories that it’s hoped will be able to see both the bubbles and their galaxies at earlier times than ever before. ...

Modeling of Lyman-alpha Emitting Galaxies and Ionized Bubbles at the Era of Reionization - Hidenobu Yajima et al
Know the quiet place within your heart and touch the rainbow of possibility; be
alive to the gentle breeze of communication, and please stop being such a jerk.
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A Volcanic Hydrogen Habitable Zone

Postby bystander » Fri Mar 10, 2017 5:14 pm

A Volcanic Hydrogen Habitable Zone
astrobites | 2017 Mar 08
Joseph Schmitt wrote:
The search for life beyond the solar system has long focused on the habitable zone (HZ). This is the region around a star where a planet with the right properties could maintain liquid water on its surface for a substantial period of time. The classical inner edge of the HZ was set using the runaway greenhouse effect, in which a positive feedback loop causes oceans to evaporate creating an oven-like world similar to Venus. The classical outer edge of the HZ was set using the maximum greenhouse effect from carbon dioxide, which is the distance at which adding carbon dioxide to a planet’s atmosphere starts cooling the planet (due to scattering the light or condensation). There have been many other calculations of the HZ edges using different assumptions, such as a nearly desert planet and planets with different masses. In this paper, the authors try to use volcanoes to expand edges of the HZ. They calculate the HZ edges for atmospheres with significant amounts of hydrogen gas produced by volcanoes, another powerful greenhouse gas. ...

A Volcanic Hydrogen Habitable Zone - Ramses M. Ramirez, Lisa Kaltenegger

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Know the quiet place within your heart and touch the rainbow of possibility; be
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