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  • richardmitnick 1:23 pm on April 19, 2018 Permalink | Reply
    Tags: Astrobites, , , , Comet 67P/Churyumov-Gerasimenko, , ,   

    From astrobites: “A ‘Breathing’ Comet” 

    Astrobites bloc

    astrobites

    Apr 19, 2018
    Jamila Pegues

    Title: Synthesis of Molecular Oxygen via Irradiation of Ice Grains in the Protosolar Nebula
    Authors: O. Mousis, T. Ronnet, J. I. Lunine, R. Maggiolo, P. Wurz, G. Danger, and A. Bouquet
    First Author’s Institution: Aix Marseille Universite, CNRS, LAM (Laboratoire d’Astrophysique de Marseille) UMR 7326, 13388, Marseille, France
    1
    Status: Accepted to The Astrophysical Journal [open access]

    2
    Figure 1: A picture of the comet 67P/C-G, taken by Rosetta in August 2014. The resolution is 5.3 meters/pixel. Image credit: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA.

    ESA Rosetta spacecraft

    In August 2014, the Rosetta orbiter met up with the comet known as 67P/Churyumov-Gerasimenko (aka, 67P/C-G). Rosetta stuck close by, watching and observing, as the comet orbited around the Sun. Now, nearly four years later, we’re still learning new science from everything Rosetta (and its lander Philae) discovered. In today’s astrobite, we focus on one comet discovery in particular: molecular oxygen.

    See the full article here .

    Please help promote STEM in your local schools.

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    What do we do?

    Astrobites is a daily astrophysical literature journal written by graduate students in astronomy. Our goal is to present one interesting paper per day in a brief format that is accessible to undergraduate students in the physical sciences who are interested in active research.
    Why read Astrobites?

    Reading a technical paper from an unfamiliar subfield is intimidating. It may not be obvious how the techniques used by the researchers really work or what role the new research plays in answering the bigger questions motivating that field, not to mention the obscure jargon! For most people, it takes years for scientific papers to become meaningful.
    Our goal is to solve this problem, one paper at a time. In 5 minutes a day reading Astrobites, you should not only learn about one interesting piece of current work, but also get a peek at the broader picture of research in a new area of astronomy.

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  • richardmitnick 9:07 am on April 18, 2018 Permalink | Reply
    Tags: Astrobites, , , , , , Triple Threat: Uncovering Triple Systems with Gravitational Waves   

    From astrobites: “Triple Threat: Uncovering Triple Systems with Gravitational Waves” 

    Astrobites bloc

    astrobites

    Apr 17, 2018
    Lisa Drummond

    Title: Detecting triple systems with gravitational wave observations
    Authors: Yohai Meiron, Bence Kocsis, Abraham Loeb
    Status: The Astrophysical Journal, open access

    The Laser Interferometer Gravitational-Wave Observatory (LIGO) collaboration has been receiving a lot of press in recent years, with a run of groundbreaking gravitational wave (GW) detections (most recently, a neutron star binary!), capturing the excitement of the astrophysics community and general public alike.

    All of the gravitational waves detected so far have been produced by compact binary mergers. This series of LIGO discoveries begs the question – where are the gravitational waves produced by triples? Triple systems are not uncommon in astrophysics – but how would we distinguish a standard compact binary coalescence signal from one produced by a tight binary in orbit around a triple companion? Todays’ paper tackles this question by identifying signatures of the triple that are apparent in the GW signal.

    What is a hierarchical triple system?

    Triple systems consist of three celestial bodies orbiting each other simultaneously. A physical triple system usually exhibits a hierarchical structure. Two of the objects form a close binary, called the inner binary, and the third companion lies on the outskirts, orbiting at distance that far exceeds the length of the inner binary separation.

    1
    Figure 1: A schematic of a stellar triple system. The inner binary (denoted with yellow arrows) orbits a third companion (blue arrows). Image from http://wondergressive.com/triple-star-system-new-gravity/.

    See the full article here .

    Please help promote STEM in your local schools.

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    What do we do?

    Astrobites is a daily astrophysical literature journal written by graduate students in astronomy. Our goal is to present one interesting paper per day in a brief format that is accessible to undergraduate students in the physical sciences who are interested in active research.
    Why read Astrobites?

    Reading a technical paper from an unfamiliar subfield is intimidating. It may not be obvious how the techniques used by the researchers really work or what role the new research plays in answering the bigger questions motivating that field, not to mention the obscure jargon! For most people, it takes years for scientific papers to become meaningful.
    Our goal is to solve this problem, one paper at a time. In 5 minutes a day reading Astrobites, you should not only learn about one interesting piece of current work, but also get a peek at the broader picture of research in a new area of astronomy.

     
  • richardmitnick 8:12 am on April 13, 2018 Permalink | Reply
    Tags: A Naked-Eye Superflare Detected from Proxima Centauri, Astrobites, , , ,   

    From astrobites: “A Naked-Eye Superflare Detected from Proxima Centauri” 

    Astrobites bloc

    astrobites

    Apr 12, 2018
    Daniel Berke

    Title: The First Naked-Eye Superflare Detected from Proxima Centauri
    Authors: Ward S. Howard, Matt A. Tilley, Hank Corbett, Allison Youngblood, R. O. Parke Loyd, Jeffrey K. Ratzloff, Octavi Fors, Daniel del Ser, Evgenya L. Shkolnik, Carl Ziegler, Erin E. Goeke, Aaron D. Pietraallo, Joshua Haislip, Nicholas M. Law
    First Author’s Institution: Department of Physics and Astronomy, University of North Carolina at Chapel Hill, North Carolina, USA
    1
    Status: Submitted to AAS Journals, open access on ArXiv

    Proxima Centauri is the closest known star to the Sun at just 4.246 light-years (1.302 parsecs) away.

    Centauris Alpha Beta Proxima 27, February 2012. Skatebiker

    It’s a red dwarf of spectral type M6 with about 12% of the Sun’s mass, 1.2 times the diameter of Jupiter, and 0.17% of the Sun’s luminosity. It hosts the closest known exoplanet to us, Proxima Centauri b, which was discovered in 2016 as covered in this Astrobite. Like our Sun, it’s on the main sequence, steadily fusing hydrogen into helium in its core. Yet this tiny star is way more active than the Sun is!

    The energy contained in the magnetic fields can be violently released in the form of stellar flares, which can grow as large as Proxima Centauri itself and reach temperatures of up to 27 million K! (Normally its effective surface temperature is around 3,000 K.) These flares from Proxima Centauri have been observed frequently in the past (for instance in this recent Astrobite).

    2
    The nearest exoplanet to Earth may get hit hard by damaging ultraviolet radiation, making it tough for life to survive there, a new study suggests. Typical superflare. No image credit.

    1
    The light curve of Proxima Centauri as seen by the Evryscope around the time of the superflare. Three weaker (but still strong) flares were detected in the aftermath of the superflare, marked by arrows. Figure 1 in the paper.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    What do we do?

    Astrobites is a daily astrophysical literature journal written by graduate students in astronomy. Our goal is to present one interesting paper per day in a brief format that is accessible to undergraduate students in the physical sciences who are interested in active research.
    Why read Astrobites?

    Reading a technical paper from an unfamiliar subfield is intimidating. It may not be obvious how the techniques used by the researchers really work or what role the new research plays in answering the bigger questions motivating that field, not to mention the obscure jargon! For most people, it takes years for scientific papers to become meaningful.
    Our goal is to solve this problem, one paper at a time. In 5 minutes a day reading Astrobites, you should not only learn about one interesting piece of current work, but also get a peek at the broader picture of research in a new area of astronomy.

     
  • richardmitnick 10:28 am on April 11, 2018 Permalink | Reply
    Tags: A White Dwarf Kicked Out of a Supernova, Astrobites, , , ,   

    From astrobites: “A White Dwarf Kicked Out of a Supernova” 

    Astrobites bloc

    astrobites

    1
    NASA/JPL-Caltech

    Title: Further insight on the hypervelocity white dwarf, LP 40-365 (GD 492): a nearby emissary from a single-degenerate Type Ia supernova
    Author: Roberto Raddi, Mark Hollands, Detlev Koester, et al.
    First Author’s Institution: University of Warwick, UK

    Status: Accepted to ApJ

    I’m sure you’ve heard of Type Ia supernovae. They’re a certain type of exploding star, most famous for the fact that their brightness can be easily calculated from the other features of the explosion. If you know how bright something is, and you measure how much of the light reaches you, that tells you how far away the light source must be; “standard candle” is the common term for objects like this. Type Ia supernovae are useful to astronomers who want to measure the distance to far-away galaxies, and they form one link in the cosmic distance ladder.

    Despite how useful Type Ia supernovae are, we still don’t fully understand how they happen. We know that you need a white dwarf, and you need that white dwarf’s mass to increase until it nears a critical point (the Chandrasekhar mass limit, which is about 1.4 times the mass of the Sun). What we don’t know is what makes a white dwarf’s mass increase to reach that point. There are two models that we usually consider for how this happens. Firstly, the white dwarf could slowly pull matter from a nearby star. Secondly, two white dwarfs could collide. The two models are often called “single-degenerate” and “double-degenerate”, because “degenerate objects” is another term for white dwarfs (a term related to the physics of their structure). The advantages and disadvantages of the two models have been debated for decades. In recent years the debate seems to have leaned more towards the double-degenerate channel for most Type Ia supernovae, and the single-degenerate channel for some unusual-looking Type Ia supernovae.

    Last year, a team of astronomers found a white dwarf named LP40-365. It’s moving through the galaxy incredibly fast (about 500–800 km/s), and it contains an unusual collection of elements. The authors of the discovery paper suggest that this is a leftover from a Type Ia supernova — a white dwarf that tried to go bang but survived. Today’s authors studied spectra of the star (from the Copernico telescope) in order to get a better idea of what is going on with it.


    Copernica Telescope located on a mountain ridge approximately 4 kilometers southeast of and 350 m higher than the town of Asiago Italy

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    What do we do?

    Astrobites is a daily astrophysical literature journal written by graduate students in astronomy. Our goal is to present one interesting paper per day in a brief format that is accessible to undergraduate students in the physical sciences who are interested in active research.
    Why read Astrobites?

    Reading a technical paper from an unfamiliar subfield is intimidating. It may not be obvious how the techniques used by the researchers really work or what role the new research plays in answering the bigger questions motivating that field, not to mention the obscure jargon! For most people, it takes years for scientific papers to become meaningful.
    Our goal is to solve this problem, one paper at a time. In 5 minutes a day reading Astrobites, you should not only learn about one interesting piece of current work, but also get a peek at the broader picture of research in a new area of astronomy.

     
  • richardmitnick 7:35 pm on April 10, 2018 Permalink | Reply
    Tags: Astrobites, , , , , not enough stellar mass: a cosmic conundrum, Too much star formation   

    From astrobites: “Too much star formation, not enough stellar mass: a cosmic conundrum” 

    Astrobites bloc

    astrobites

    Title: ON THE INCONSISTENCY BETWEEN COSMIC STELLAR MASS DENSITY AND STAR FORMATION RATE UP TO z ~ 8
    Authors: H. Yu & F. Y. Wang
    First author’s institution: Nanjing University
    1
    Status: Published in the Astrophysical Journal, Open Access

    The universe is a pretty efficient star making machine. Since around a billion years after the Big Bang, galaxies have been assembling and forming stars with abandon. Many of these stars have now died, particularly the most massive, which have much shorter lifetimes than less massive stars, and often end their lives in cataclysmic supernovae. But a number of low mass stars are still around from the very earliest star forming episodes. As a result, the overall density of stars in the universe has been increasing. Figure 1, from today’s paper, shows the Stellar Mass Density (SMD) from recent observations – the stellar mass density is peaked at the current day (redshift zero)

    2
    Figure 1: Top: The stellar mass density (SMD; mass in stars per unit volume) of the universe over cosmic time. The green and blue points show recent observations. The red line, with grey error regions, is the best fit to the observed data. The solid black and dashed black lines show the inferred density from star formation history (SFH) observations. Middle: the ratio of SMD with a constant recycling factor to an evolving recycling factor. Bottom: Ratio of the SFH fit to the SMD fit.

    However, a key discovery over the past few decades is that the universe is not forming stars with quite the same enthusiasm as it once was. In fact, the peak of star formation activity in the universe was around ten billion years ago, or three and a half billion years after the Big Bang. Since then, the Star Formation Rate Density (SFRD, the mass in stars formed per unit volume) has been gradually decreasing.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    What do we do?

    Astrobites is a daily astrophysical literature journal written by graduate students in astronomy. Our goal is to present one interesting paper per day in a brief format that is accessible to undergraduate students in the physical sciences who are interested in active research.
    Why read Astrobites?

    Reading a technical paper from an unfamiliar subfield is intimidating. It may not be obvious how the techniques used by the researchers really work or what role the new research plays in answering the bigger questions motivating that field, not to mention the obscure jargon! For most people, it takes years for scientific papers to become meaningful.
    Our goal is to solve this problem, one paper at a time. In 5 minutes a day reading Astrobites, you should not only learn about one interesting piece of current work, but also get a peek at the broader picture of research in a new area of astronomy.

     
  • richardmitnick 11:16 am on February 22, 2018 Permalink | Reply
    Tags: Astrobites, , , , , PEPSI technology   

    From astrobites: “Deep Spectra with PEPSI” 

    Astrobites bloc

    astrobites

    Title: PEPSI deep spectra III: A chemical analysis of the ancient planet-host star Kepler−444
    https://arxiv.org/abs/1712.06986
    Authors: C. E. Mack III, K. G. Strassmeier, I. Ilyin, S. C. Schuler, F. Spada, and S. A. Barnes
    First Author’s Institution: Leibnitz Institute for Astrophysics Potsdam
    1
    Status: In press in Astronomy & Astrophysics, open access

    More and more information can be squeezed out of spectra at ever higher resolutions and over longer wavelength ranges. Today, one cutting-edge spectrograph at visible wavelengths is the Potsdam Echelle Polarimetric and Spectroscopic Instrument (PEPSI) at the Large Binocular Telescope (LBT) on Mt. Graham in Arizona. Cunningly, PEPSI was build to take data from three different telescopes on Mt. Graham. They include 1.) the LBT itself, with twin 8.4 m primary mirrors; 2.) the nearby 1.8 m Vatican Advanced Technology Telescope (VATT) through an underground cable; and 3.) a tiny, effectively 13 mm solar telescope on the LBT patio, right next to the barbeque.

    U Arizona Large Binocular Telescope, Mount Graham, Arizona, USA, Altitude 3,221 m (10,568 ft)

    Vatican Advanced Technology Telescope, U Arizona Steward Observatory, Altitude 792 meters (2,598 ft)

    The hydra-headed PEPSI can produce spectra with a resolution of up to around λ/Δλ=270,000 between wavelengths of about 380 to 910 nm. The first deep spectral data from PEPSI are just now coming out in a set of three papers, and we’ll look at one of them, a chemical analysis of a planet-hosting star.

    See the full article here .

    Please help promote STEM in your local schools.

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    What do we do?

    Astrobites is a daily astrophysical literature journal written by graduate students in astronomy. Our goal is to present one interesting paper per day in a brief format that is accessible to undergraduate students in the physical sciences who are interested in active research.
    Why read Astrobites?

    Reading a technical paper from an unfamiliar subfield is intimidating. It may not be obvious how the techniques used by the researchers really work or what role the new research plays in answering the bigger questions motivating that field, not to mention the obscure jargon! For most people, it takes years for scientific papers to become meaningful.
    Our goal is to solve this problem, one paper at a time. In 5 minutes a day reading Astrobites, you should not only learn about one interesting piece of current work, but also get a peek at the broader picture of research in a new area of astronomy.

     
  • richardmitnick 1:47 pm on February 19, 2018 Permalink | Reply
    Tags: Astrobites, , , , ,   

    From astrobites: “Big light comes from small clusters” 

    Astrobites bloc

    astrobites

    Title: The Little Engines That Could? Globular Clusters Contribute Significantly to Reionization-era Star Formation
    Authors: Michael Boylan-Kolchin
    First Author’s Institution: University of Texas, Austin, TX, USA

    Status: Submitted to Monthly Notices of the Royal Astronomical Society, open access via arXiv

    This article was previously covered on Astrobites, but here is another Astrobiter’s take on it!

    When the lights went on.

    Reionization era and first stars, Caltech

    The Epoch of Reionization (EoR), as its name suggests, is the relic of a very ionizing (read exciting) time in the evolutionary history of our universe. It is the time when the first stars are thought to have lived and died, as light emerged in the darkness of the cosmos, for the first time after recombination. Leading up to this point, the universe had been unobservable for millions of years due to the presence of neutral hydrogen that blocks any high energy photons capable of ionizing the medium by absorbing them. However, something during the reionization epoch provided enough light to strip the electrons off of all the existing neutral atoms, making it possible to peer back into the formation of first stars and galaxies.

    Finding the culprit.

    Today, what exactly caused reionization remains a puzzle that many scientists are eager to solve. Sources such as supernovae, active galactic nuclei, binary mergers, and more recently, faint dwarf galaxies have all been posited as significant contributors of ionizing photons. Regrettably, constraining them with observations, especially in the case of faint sources, is far from easy and continues to render the pursuit inconclusive.

    In the wake of this situation, author Boylan-Kolchin turns his eye towards something that has long been a corner-stone of the study of early galaxies. These objects are tightly bound collection of stars a.k.a globular clusters (GCs), whose numerousness and ancient origin (coinciding with the EoR) make them important objects in the context of cosmic reionization. In his work, the author seeks to theoretically infer the contribution of GCs to reionization, and spell out its implications. Using the number density and stellar mass distribution of GCs from local observations, and a uniform rate of formation over 1 Gyr (redshift z ~ 4-10), he artificially synthesizes stellar populations characteristic of a GC to obtain its ultraviolet luminosity function (UVLF; the number distribution per unit volume and magnitude in ultraviolet wavelengths) at various epochs.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    What do we do?

    Astrobites is a daily astrophysical literature journal written by graduate students in astronomy. Our goal is to present one interesting paper per day in a brief format that is accessible to undergraduate students in the physical sciences who are interested in active research.
    Why read Astrobites?

    Reading a technical paper from an unfamiliar subfield is intimidating. It may not be obvious how the techniques used by the researchers really work or what role the new research plays in answering the bigger questions motivating that field, not to mention the obscure jargon! For most people, it takes years for scientific papers to become meaningful.
    Our goal is to solve this problem, one paper at a time. In 5 minutes a day reading Astrobites, you should not only learn about one interesting piece of current work, but also get a peek at the broader picture of research in a new area of astronomy.

     
  • richardmitnick 12:27 pm on February 8, 2018 Permalink | Reply
    Tags: Astrobites, , , , , How much does the Milky… weigh?   

    From astrobites: “How much does the Milky… weigh?” 

    Astrobites bloc

    astrobites

    Title: What galaxy masses perturb the local cosmic expansion?
    Authors: Jorge Penarrubia & Azadeh Fattahi
    First Author’s Institution: Institute for Astronomy, University of Edinburgh, Royal Observatory
    1
    Status: Published in MNRAS, open access

    Picture this: you’re at your local clinic for an annual physical, and your doctor asks to measure your weight. Simple, right? But now, imagine your doctor doesn’t have a scale, nor the ability to lift you, nor any understanding of what your body is made of. Oh, and you’re invisible, too. Not so simple anymore…

    This is (more or less) the challenge astrophysicists face when trying the measure the mass of the Milky Way, our humble galactic home. And even though this has been an active area of research for nearly 60 years, today’s best estimates still vary widely from one another (see figure 1 for a few recent examples). Back at your annual physical, it’s as if your doctor tells you, “I think you weigh about 150 lbs, give or take 80 lbs.”

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    Figure 1: Fourteen recent mass estimates of the Milky Way produced since 1999, obtained through a variety of different methods. Note how the estimates vary significantly from each other, by up to a factor of 5. Figure adapted from Table 8 in Hawthorn & Gerhard 2017.

    A guide to measuring heavy, invisible things

    Like other galaxies, much of the Milky Way’s mass comes in the form of dark matter, which is a bit of a bummer, because we can’t see it. What we can see are visible objects – like stars, gas clouds, or dust particles – whose motion is a tell-tale for the dark matter density around them (this Astrobite and this one provide a great overview of how this is done in practice). So in order to measure the total mass of the galaxy (often referred to as the galaxy’s virial mass), we need to find observable objects all the way out to the galaxy’s edge. The issue is that out at the fringes of our galaxy, visible tracers are few and hard to find. This is one of the main causes of the large uncertainty in our estimate of the Milky Way’s mass.

    Fortunately, there are a few other theoretical approaches to measuring the total mass of a galaxy. And these methods do not rely as heavily on observing faint objects at the outskirts of galaxies. Today’s paper discusses several of these, and specifically one that involves measuring the mass of a galaxy based on how it perturbs the local Hubble flow (or in other words, how its gravitational force affects the motion of other galaxies far beyond its own boundaries, where the expansion of the universe is the dominant effect). In theory, the mass derived from the perturbed Hubble flow is equal to the virial mass of the galaxy, which could be a big deal because we can theoretically calculate the mass of the Milky Way without needing to find faint objects at the edge of the galaxy!

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    Figure 2: 6 of the 12 APOSTLE simulations. The two dashed circles represent the boundaries of the galaxy equivalents of the Milky Way and Andromeda, and the solid circle represents a 3 Mpc radius around the pair of galaxies, inside of which one can measure their influence on the Hubble Flow. Figure 2 in the paper.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    What do we do?

    Astrobites is a daily astrophysical literature journal written by graduate students in astronomy. Our goal is to present one interesting paper per day in a brief format that is accessible to undergraduate students in the physical sciences who are interested in active research.
    Why read Astrobites?

    Reading a technical paper from an unfamiliar subfield is intimidating. It may not be obvious how the techniques used by the researchers really work or what role the new research plays in answering the bigger questions motivating that field, not to mention the obscure jargon! For most people, it takes years for scientific papers to become meaningful.
    Our goal is to solve this problem, one paper at a time. In 5 minutes a day reading Astrobites, you should not only learn about one interesting piece of current work, but also get a peek at the broader picture of research in a new area of astronomy.

     
  • richardmitnick 11:24 am on February 7, 2018 Permalink | Reply
    Tags: Astrobites, , , , , , The Deepest Rumblings of the Sun   

    From astrobites: “The Deepest Rumblings of the Sun” 

    Astrobites bloc

    astrobites

    Feb 7, 2018
    Avery Schiff

    Title: Asymptotic g modes: Evidence for a rapid rotation of the solar core
    Authors: Eric Fossat, Patrick Boumier, Thierry Corbard, et al.
    First Author’s Institution: Université Côte d’Azur, Observatoire Côte d’Azur, France
    1
    Status: Published in Astronomy and Astrophysics, open access

    Far below its surface, the Sun slowly breaths with invisible pulses. Blobs of plasma are launched upwards by buoyant forces, only to reach the peak of their trajectories and plunge back to the depths below. This motion is known as a g-mode oscillation, and until recently it was unseen by solar scientists. In today’s paper, Fossat et al. describe one of the most promising detections of the g-modes to date and the implications for the Sun’s deepest layers.

    Helioseismology

    While the Sun appears constant in brightness to the naked eye, careful telescope observations reveal that it periodically dims and brightens on a miniscule scale. Just as a song is made from many notes, the flickering occurs at countless different frequencies that create the “music” of the Sun. Helioseismology, an observation technique that tracks vibrations deep into the Sun, uses Fourier analysis to determine which frequencies are most important and study three potential sources of brightness fluctuations on the Sun: p-mode, g-mode, and f-mode oscillations. Since the brightness of plasma is strongly related to the density, each mode is associated with material compressing or decompressing in some way. P-mode and f-mode oscillations are frequently observed at the solar surface, but the g-modes lurk far beneath the surface of the Sun. By studying g-modes, we are studying the lowest depths of the Sun far below what is visible to us.

    2
    Figure 1: An illustration of the layers of the sun. While p-mode oscillations are able to travel from the surface all the way to the core, g-modes are unable to escape the radiative zone. Credit: ESA

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    What do we do?

    Astrobites is a daily astrophysical literature journal written by graduate students in astronomy. Our goal is to present one interesting paper per day in a brief format that is accessible to undergraduate students in the physical sciences who are interested in active research.
    Why read Astrobites?

    Reading a technical paper from an unfamiliar subfield is intimidating. It may not be obvious how the techniques used by the researchers really work or what role the new research plays in answering the bigger questions motivating that field, not to mention the obscure jargon! For most people, it takes years for scientific papers to become meaningful.
    Our goal is to solve this problem, one paper at a time. In 5 minutes a day reading Astrobites, you should not only learn about one interesting piece of current work, but also get a peek at the broader picture of research in a new area of astronomy.

     
  • richardmitnick 8:37 am on February 1, 2018 Permalink | Reply
    Tags: Astrobites, , , , , Post-starburst galaxies: the missing link in galaxy evolution?   

    From astrobites: “Post-starburst galaxies: the missing link in galaxy evolution?” 

    Astrobites bloc

    astrobites

    Feb 1, 2018
    Joanna Ramasawmy

    Title: Massive post-starburst galaxies at z > 1 are compact proto-spheroids
    Authors: Omar Almaini, Vivienne Wild, David T. Maltby, William G. Hartley, Chris Simpson, Nina A. Hatch, Ross J. McLure, James S. Dunlop, Kate Rowlands
    First Author’s Institution: School of Physics and Astronomy, University of Nottingham, University Park, Nottingham NG7 2RD, U.K
    1
    Status: Accepted for publication in MNRAS, open access

    2
    NGC 5090 and 5091, a pair of interacting galaxies which show two different morphologies, or galaxy shapes. NGC 5090 is an elliptical galaxy, whereas NGC 5091 is a disc-shaped spiral galaxy. Source: ESO.

    Surveys of the nearby universe show that we can divide galaxies into two types if we look at their colours — we find a “blue cloud” of star-forming galaxies, and “red sequence” of passive ellipticals without active star formation. Besides their colours, there is another important difference between these two types of galaxies: their shape, or morphology. It turns out that most blue galaxies have a disc shape, while red galaxies are spheroidal. The majority of massive galaxies we see around us are spheroidal passive galaxies. But how and when do galaxies evolve from star-forming discs to red-and-dead spheroids?

    In this paper, the authors investigate post-starburst galaxies (PSBs, or E+A galaxies as described in the astrobites galaxy classification guide), which are galaxies that have only recently stopped forming stars. One narrative of galaxy evolution suggests that galaxies move from the blue cloud to the red sequence following a rapid quenching of star formation. By shutting down star formation, the hot blue stars rapidly die out and the galaxy is left with an old red stellar population, explaining the transition in colour. However, this doesn’t explain the additional structural transformation that changes galaxies from a disc to a spheroid morphology. PSBs, rare galaxies caught in this transition phase, might hold the key.

    PSBs are traditionally identified by their spectral features, usually the strong absorption lines associated with the A-type stars that dominate these galaxies’ starlight. However, spectroscopy limits us to looking at nearby, bright galaxies. Very distant galaxies are much fainter and so require very long exposure times on the most expensive space telescopes. The authors of this paper use a novel technique, identifying “supercolours” that allow them to categorise galaxies using just photometric data — which is much cheaper as it can be done from the ground! This method allows them to obtain a large sample of galaxies at high redshifts (z > 1), investigating an earlier period in the history of the universe than other studies of PSBs. The authors are interested in two properties of PSBs: the size (or compactness), and the morphological shape. The authors then compare these properties of PSBs to those of the blue cloud and red sequence galaxy populations.

    See the full article here .

    Please help promote STEM in your local schools.

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    What do we do?

    Astrobites is a daily astrophysical literature journal written by graduate students in astronomy. Our goal is to present one interesting paper per day in a brief format that is accessible to undergraduate students in the physical sciences who are interested in active research.
    Why read Astrobites?

    Reading a technical paper from an unfamiliar subfield is intimidating. It may not be obvious how the techniques used by the researchers really work or what role the new research plays in answering the bigger questions motivating that field, not to mention the obscure jargon! For most people, it takes years for scientific papers to become meaningful.
    Our goal is to solve this problem, one paper at a time. In 5 minutes a day reading Astrobites, you should not only learn about one interesting piece of current work, but also get a peek at the broader picture of research in a new area of astronomy.

     
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