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  • richardmitnick 3:07 pm on January 28, 2023 Permalink | Reply
    Tags: "Searching for the Seeds of Supermassive Black Holes", AAS NOVA, , , , ,   

    From AAS NOVA: “Searching for the Seeds of Supermassive Black Holes” 

    AASNOVA

    From AAS NOVA

    1.27.23
    Colin Stuart

    1
    This Hubble Space Telescope image shows the spiral galaxy NGC 4051, which is classified as an active galaxy. Nearby active galaxies like NGC 4051 might be good analogues for the galaxies that hosted the seeds of supermassive black holes early in the universe. [D. Crenshaw and O. Fox/NASA/ESA Hubble CC BY 4.0]

    Astronomers are still trying to figure out exactly how supermassive black holes form. They may be the result of smaller black holes combining, and a new study says that these smaller black holes could show up in an upcoming survey with JWST.

    It Starts with a Seed

    The biggest black holes in the universe can tip the scales at billions of solar masses. What’s more, the first ones formed within a couple of hundred million years of the Big Bang. Just how did the universe build such gargantuan objects so quickly?

    Usually black holes form when a massive star dies, but no single star could birth a black hole that big. Instead, like flowers, supermassive black holes probably grow from seeds. Perhaps the smaller black holes created by the deaths of the first massive stars merged. This could create black holes up to a thousand solar masses, which gravity could then combine into supermassive black holes. Black holes up to a million solar masses may have formed directly from the gravitational collapse of dense gas clouds in the early universe. They too would merge over time.

    Finding a seed that has yet to germinate into a supermassive black hole would allow astronomers to see the process in action. Andy Goulding and Jenny Greene (both Princeton University) have recently investigated whether black hole seeds could reveal themselves in upcoming deep sky surveys with JWST. They focus on black holes with approximately one million solar masses at redshifts between 7 and 10.

    Colour Differences

    By definition a black hole is invisible. Its gravitational pull is so intense that it swallows all light that falls upon it. Yet black holes often reveal themselves through their accretion discs — the super-heated queue of material waiting to be devoured. Their accretion discs are often bright enough to be seen across most of the visible universe. These bright centres of distant galaxies are called active galactic nuclei.

    In their study, Goulding and Greene combined templates of active galactic nuclei at lower redshifts with mock galaxy catalogs specifically created for JWST. They concluded that the best local analogs of distant seed black hole active galactic nuclei are Seyfert I galaxies — active galaxies with broad emission lines in their spectra. The ultraviolet emission of black hole seeds and Seyfert I galaxies is expected to be similar.

    They then looked at whether these active galactic nuclei could show up in the upcoming JWST Advanced Deep Extragalactic Survey (JADES). They found that a distant active galactic nucleus powered by a seed black hole should appear a different colour to the rest of the galaxy in images taken by JWST’s Near Infrared Camera (NIRCam). Specifically, the galaxy will appear blue and the nucleus will be redder.

    While it’s hard to put an exact figure on it, Goulding and Greene estimated that astronomers might expect to find a few to tens of seed black holes within a one hundred square arcminute field. Perhaps then we’ll finally start to understand how supermassive black holes came to reside in the heart of almost every galaxy in the universe.

    Citation

    “An Empirical Approach to Selecting the First Growing Black Hole Seeds with JWST/NIRCam,” Andy D. Goulding and Jenny E. Greene 2022 ApJL 938 L9.
    https://iopscience.iop.org/article/10.3847/2041-8213/ac9614/pdf
    See the science paper for instructive material with images.

    See the full article here .

    Comments are invited and will be appreciated, especially if the reader finds any errors which I can correct. Use “Reply”.


    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.


    Stem Education Coalition

    1

    The mission of the American Astronomical Society is to enhance and share humanity’s scientific understanding of the Universe.

    The Society, through its publications, disseminates and archives the results of astronomical research. The Society also communicates and explains our understanding of the universe to the public.
    The Society facilitates and strengthens the interactions among members through professional meetings and other means. The Society supports member divisions representing specialized research and astronomical interests.
    The Society represents the goals of its community of members to the nation and the world. The Society also works with other scientific and educational societies to promote the advancement of science.
    The Society, through its members, trains, mentors and supports the next generation of astronomers. The Society supports and promotes increased participation of historically underrepresented groups in astronomy.
    The Society assists its members to develop their skills in the fields of education and public outreach at all levels. The Society promotes broad interest in astronomy, which enhances science literacy and leads many to careers in science and engineering.

    Adopted June 7, 2009

    The society was founded in 1899 through the efforts of George Ellery Hale. The constitution of the group was written by Hale, George Comstock, Edward Morley, Simon Newcomb and Edward Charles Pickering. These men, plus four others, were the first Executive Council of the society; Newcomb was the first president. The initial membership was 114. The AAS name of the society was not finally decided until 1915, previously it was the “Astronomical and Astrophysical Society of America”. One proposed name that preceded this interim name was “American Astrophysical Society”.

    The AAS today has over 7,000 members and six divisions – the Division for Planetary Sciences (1968); the Division on Dynamical Astronomy (1969); the High Energy Astrophysics Division (1969); the Solar Physics Division (1969); the Historical Astronomy Division (1980); and the Laboratory Astrophysics Division (2012). The membership includes physicists, mathematicians, geologists, engineers and others whose research interests lie within the broad spectrum of subjects now comprising contemporary astronomy.

    In 2019 three AAS members were selected into the tenth anniversary class of TED Fellows.

    The AAS established the AAS Fellows program in 2019 to “confer recognition upon AAS members for achievement and extraordinary service to the field of astronomy and the American Astronomical Society.” The inaugural class was designated by the AAS Board of Trustees and includes an initial group of 232 Legacy Fellows.

     
  • richardmitnick 5:24 pm on January 27, 2023 Permalink | Reply
    Tags: "The Corgi of Exoplanets - Methane Mystery", AAS NOVA, , , , Exoplanet HAT-P-18b, , , ,   

    From AAS NOVA And The NASA/ESA/CSA James Webb Space Telescope: “The Corgi of Exoplanets – Methane Mystery” 

    AASNOVA

    From AAS NOVA

    And

    NASA Webb Header

    National Aeronautics Space Agency/European Space Agency [La Agencia Espacial Europea] [Agence spatiale européenne][Europäische Weltraumorganization](EU)/ Canadian Space Agency [Agence Spatiale Canadienne](CA) James Webb Infrared Space Telescope annotated, finally launched December 25, 2021, ten years late.

    The NASA/ESA/CSA James Webb Space Telescope

    1.20.23
    Ben Cassese

    1
    An artist’s depiction of a transiting exoplanet with an escaping helium tail. [M. Kornmesserr, NASA/ESA Hubble CC BY 4.0]

    With JWST up and running, astronomers are getting a first look at the quirks of individual exoplanets. Features never before examined are coming into view: for instance, a recent study has revealed that while HAT-P-18b may not have much methane, it does have a tiny tail.

    JWST Shows Off, Finds a Corgi

    Now more than a year past its launch, JWST is finally doing what it was designed to do: collecting photons and wowing astronomers with the precision of its data. One of the earliest flexes of its scientific power occurred last summer, when it trained its attention on the transit of a Jupiter-sized, Saturn-mass exoplanet named HAT-P-18b.

    While the team, led by Guangwei Fu (Johns Hopkins University), found several molecules in the upper atmosphere of the planet using the Near Infrared Imager and Slitless Spectrograph (NIRISS) instrument [below], what they didn’t find was more surprising.

    3
    A subsample of the data, orange, and the best-fit model, blue, showing the helium absorption signature. The y-axis is in units of transit depth, meaning enhanced absorption appears as a positive bump. [Fu et al. 2022]

    The first of these surprises was a helium absorption signature, but not surrounding the planet: instead, their results indicate that HAT-P-18b is dragging along a faint tail of escaping helium. Similar features have been spotted trailing behind other planets, but this one was so subtle that it was previously missed by ground based observatories. In other words, HAT-P-18b is the corgi of the exoplanets: it has a tail, but it’s not a dominant structure.

    But what about methane?

    The second surprise concerned a molecule not displaced from the planet, but possibly missing entirely. One of the primary motivations for targeting HAT-P-18b specifically is its position in a uniquely helpful corner of parameter space for modelers working on a methane mystery.

    Hot planets with surface temperatures over 1000K are not expected to have any methane in their atmospheres, since thermodynamics at these extreme conditions prefer other species. However, simple models suggest that any worlds cooler than this should show signs of absorption caused by methane molecules in the upper atmosphere intercepting photons with a specific wavelength.

    Strangely, however, this prediction has not panned out in previous studies. Searches of several planets that should have held methane turned up none. This tension called for a closer look: were the assumptions baked into the models wrong, or was there something strange about the first worlds surveyed? With an equilibrium temperature of 800K, HAT-P-18b was the perfect target to help move the needle one way or another.

    3
    The NIRISS data, black, and several possible model atmospheres to explain it, colored on top. The green and red models were produced assuming equilibrium chemistry. The x-axis denotes wavelength, and the ticks range linearly from 0.5 to 2.5 microns. [Fu et al. 2022]

    Fu and collaborators made no conclusive methane detection, further deepening the model mismatch puzzle. Models which assume the atmosphere is in chemical equilibrium struggled to reproduce the combination of no-methane, yes-water seen in the data, which suggested that some other mechanism(s) were involved to remove the expected gas. Even more striking, other models which made no assumption about an equilibrium also did not confidently prefer including methane in the final fit over leaving it out entirely.

    In all, JWST revealed HAT-P-18b to be a strange world, one which subverts our expectations of atmospheric chemistry but charms with a helium tail. We’ll have to wait for JWST observations of other planets before we know just how weird either of those traits truly is.

    Citation

    Water and an Escaping Helium Tail Detected in the Hazy and Methane-depleted Atmosphere of HAT-P-18b from JWST NIRISS/SOSS, Guangwei Fu et al 2022 ApJL 940 L35.
    https://iopscience.iop.org/article/10.3847/2041-8213/ac9977/pdf
    See the science paper for instructive material with images.

    See the full article here .

    Comments are invited and will be appreciated, especially if the reader finds any errors which I can correct. Use “Reply”.


    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.


    Stem Education Coalition

    The NASA/ESA/CSA James Webb Space Telescope is a large infrared telescope with a 6.5-meter primary mirror. Webb was finally launched December 25, 2021, ten years late. Webb will be the premier observatory of the next decade, serving thousands of astronomers worldwide. It will study every phase in the history of our Universe, ranging from the first luminous glows after the Big Bang, to the formation of solar systems capable of supporting life on planets like Earth, to the evolution of our own Solar System.

    Webb is the world’s largest, most powerful, and most complex space science telescope ever built. Webb will solve mysteries in our solar system, look beyond to distant worlds around other stars, and probe the mysterious structures and origins of our universe and our place in it.

    Webb was formerly known as the “Next Generation Space Telescope” (NGST); it was renamed in Sept. 2002 after a former NASA administrator, James Webb.

    Webb is an international collaboration between National Aeronautics and Space Administration, the European Space Agency (ESA), and the Canadian Space Agency (CSA). The NASA Goddard Space Flight Center managed the development effort. The main industrial partner is Northrop Grumman; the Space Telescope Science Institute operates Webb.

    Several innovative technologies have been developed for Webb. These include a folding, segmented primary mirror, adjusted to shape after launch; ultra-lightweight beryllium optics; detectors able to record extremely weak signals, microshutters that enable programmable object selection for the spectrograph; and a cryocooler for cooling the mid-IR detectors to 7K.

    There are four science instruments on Webb: The Near InfraRed Camera (NIRCam), The Near InfraRed Spectrograph (NIRspec), The Mid-InfraRed Instrument (MIRI), and The Fine Guidance Sensor/ Near InfraRed Imager and Slitless Spectrograph (FGS-NIRISS).

    Webb’s instruments are designed to work primarily in the infrared range of the electromagnetic spectrum, with some capability in the visible range. It will be sensitive to light from 0.6 to 28 micrometers in wavelength.
    National Aeronautics Space Agency Webb NIRCam.

    The European Space Agency [La Agencia Espacial Europea] [Agence spatiale européenne][Europäische Weltraumorganization](EU) Webb MIRI schematic.

    Webb has four main science themes: The End of the Dark Ages: First Light and Reionization, The Assembly of Galaxies, The Birth of Stars and Protoplanetary Systems, and Planetary Systems and the Origins of Life.

    Launch was December 25, 2021, ten years late, on an Ariane 5 rocket. The launch was from Arianespace’s ELA-3 launch complex at European Spaceport located near Kourou, French Guiana. Webb is located at the second Lagrange point, about a million miles from the Earth.

    ESA50 Logo large

    Canadian Space Agency

    1

    The mission of the American Astronomical Society is to enhance and share humanity’s scientific understanding of the Universe.

    The Society, through its publications, disseminates and archives the results of astronomical research. The Society also communicates and explains our understanding of the universe to the public.
    The Society facilitates and strengthens the interactions among members through professional meetings and other means. The Society supports member divisions representing specialized research and astronomical interests.
    The Society represents the goals of its community of members to the nation and the world. The Society also works with other scientific and educational societies to promote the advancement of science.
    The Society, through its members, trains, mentors and supports the next generation of astronomers. The Society supports and promotes increased participation of historically underrepresented groups in astronomy.
    The Society assists its members to develop their skills in the fields of education and public outreach at all levels. The Society promotes broad interest in astronomy, which enhances science literacy and leads many to careers in science and engineering.

    Adopted June 7, 2009

    The society was founded in 1899 through the efforts of George Ellery Hale. The constitution of the group was written by Hale, George Comstock, Edward Morley, Simon Newcomb and Edward Charles Pickering. These men, plus four others, were the first Executive Council of the society; Newcomb was the first president. The initial membership was 114. The AAS name of the society was not finally decided until 1915, previously it was the “Astronomical and Astrophysical Society of America”. One proposed name that preceded this interim name was “American Astrophysical Society”.

    The AAS today has over 7,000 members and six divisions – the Division for Planetary Sciences (1968); the Division on Dynamical Astronomy (1969); the High Energy Astrophysics Division (1969); the Solar Physics Division (1969); the Historical Astronomy Division (1980); and the Laboratory Astrophysics Division (2012). The membership includes physicists, mathematicians, geologists, engineers and others whose research interests lie within the broad spectrum of subjects now comprising contemporary astronomy.

    In 2019 three AAS members were selected into the tenth anniversary class of TED Fellows.

    The AAS established the AAS Fellows program in 2019 to “confer recognition upon AAS members for achievement and extraordinary service to the field of astronomy and the American Astronomical Society.” The inaugural class was designated by the AAS Board of Trustees and includes an initial group of 232 Legacy Fellows.

     
  • richardmitnick 9:01 pm on January 25, 2023 Permalink | Reply
    Tags: "A Survey of Shredded Stars", AAS NOVA, , , , ,   

    From AAS NOVA: “A Survey of Shredded Stars” 

    AASNOVA

    From AAS NOVA

    1.25.23
    Kerry Hensley

    1
    Artist’s by now iconic impression of a tidal disruption event — the ripping apart of a star by a black hole. NASA/JPL-Caltech.

    A recent study of stars ripped apart by black holes — tidal disruption events — gives insight into the properties of these rare events and reveals a new category of events that lack strong spectral features.

    Disruptive Encounters
    2
    An example light curve of a tidal disruption event. Click to enlarge. [Adapted from Hammerstein et al. 2022]

    When a star passes too close to a black hole, the black hole’s powerful tidal forces spaghettify the star, stretching and elongating it until it’s eventually ripped apart. Some of the doomed star’s gas spirals toward the black hole, forming a superheated accretion disk that shines across the electromagnetic spectrum, acting like a beacon that draws our attention toward an otherwise hidden black hole.

    By collecting light curves and spectra of tidal disruption events as they brighten and fade over the course of months or years, astronomers have learned much about these dramatic events. In a recent publication, researchers tackled a new sample of shredded stars, aiming to understand how their spectral signatures and light curves map to their underlying physical properties.

    Sorting Spectra and Lining Up Light Curves

    3
    A subset of the tidal disruption event–hosting galaxies identified in the study. [Adapted from Hammerstein et al. 2022]

    While the tidal disruption events in the team’s sample have similar colors and light curves, their spectra revealed hidden differences; the strength of hydrogen and helium emission lines varied from event to event, and some events had no hydrogen or helium emission lines at all, revealing a previously unknown class of featureless tidal disruption events. When Hammerstein and collaborators used models to delve into their curated sample of events, they found that the featureless events tended to occur around more massive black holes, and events showing only helium emission lines involved more massive stars than the other three spectral classes.

    More to Learn

    4
    Cumulative distribution of the mass of the disrupted star for each of the four spectral types: featureless (black), hydrogen emission features (red), helium emission features (blue), hydrogen and helium emission features (green). [Hammerstein et al. 2022]

    Analyzing the events’ light curves revealed further trends (too many to discuss here — be sure to check out the science paper!), such as a potential connection between the maximum brightness of an event and how long it takes to fade.

    As is often the case when we begin to study increasingly large samples of rare phenomena, the data tend to both provide hints and pose questions. Future observatories and surveys tailored to detecting transient events, such as the decade-long Legacy Survey of Space and Time that will kick off at the Vera C. Rubin Observatory in 2024, are poised to reveal many more tidal disruption events — guiding us toward a better understanding of torn-apart stars.

    Citation

    The Final Season Reimagined: 30 Tidal Disruption Events from the ZTF-I Survey, Erica Hammerstein et al 2023 ApJ 942 9.
    https://iopscience.iop.org/article/10.3847/1538-4357/aca283/pdf
    See the science paper for instructive material with images.

    See the full article here .

    Comments are invited and will be appreciated, especially if the reader finds any errors which I can correct. Use “Reply”.


    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.


    Stem Education Coalition

    1

    The mission of the American Astronomical Society is to enhance and share humanity’s scientific understanding of the Universe.

    The Society, through its publications, disseminates and archives the results of astronomical research. The Society also communicates and explains our understanding of the universe to the public.
    The Society facilitates and strengthens the interactions among members through professional meetings and other means. The Society supports member divisions representing specialized research and astronomical interests.
    The Society represents the goals of its community of members to the nation and the world. The Society also works with other scientific and educational societies to promote the advancement of science.
    The Society, through its members, trains, mentors and supports the next generation of astronomers. The Society supports and promotes increased participation of historically underrepresented groups in astronomy.
    The Society assists its members to develop their skills in the fields of education and public outreach at all levels. The Society promotes broad interest in astronomy, which enhances science literacy and leads many to careers in science and engineering.

    Adopted June 7, 2009

    The society was founded in 1899 through the efforts of George Ellery Hale. The constitution of the group was written by Hale, George Comstock, Edward Morley, Simon Newcomb and Edward Charles Pickering. These men, plus four others, were the first Executive Council of the society; Newcomb was the first president. The initial membership was 114. The AAS name of the society was not finally decided until 1915, previously it was the “Astronomical and Astrophysical Society of America”. One proposed name that preceded this interim name was “American Astrophysical Society”.

    The AAS today has over 7,000 members and six divisions – the Division for Planetary Sciences (1968); the Division on Dynamical Astronomy (1969); the High Energy Astrophysics Division (1969); the Solar Physics Division (1969); the Historical Astronomy Division (1980); and the Laboratory Astrophysics Division (2012). The membership includes physicists, mathematicians, geologists, engineers and others whose research interests lie within the broad spectrum of subjects now comprising contemporary astronomy.

    In 2019 three AAS members were selected into the tenth anniversary class of TED Fellows.

    The AAS established the AAS Fellows program in 2019 to “confer recognition upon AAS members for achievement and extraordinary service to the field of astronomy and the American Astronomical Society.” The inaugural class was designated by the AAS Board of Trustees and includes an initial group of 232 Legacy Fellows.

     
  • richardmitnick 5:54 pm on January 7, 2023 Permalink | Reply
    Tags: "From the Laboratory to CW Leonis - A Hunt for a Metallic Molecule", "Isotopologues": molecules with the same chemical formula and structure in which one or more atoms has a different number of neutrons., AAS NOVA, , Astronomers have discovered more than 200 molecules in space since the first molecule was found in 1937., , , , CW Leonis is a carbon star: a supergiant star with a high abundance of carbon in its atmosphere., In order to be confident that we’ve discovered a molecule in space we need to know its spectrum., In the cold sparse space environment individual atoms can link up to form complex molecules., One of the best sites to study extraterrestrial molecules is in the dusty shroud and outflows of the star CW Leonis., , Searching Space for Chemical Compounds, Space based UV Astronomy, The chemistry of interstellar and circumstellar space, The team focused their search on magnesium dicarbide (MgC2).   

    From AAS NOVA: “From the Laboratory to CW Leonis – A Hunt for a Metallic Molecule” 

    AASNOVA

    From AAS NOVA

    1.4.23
    Kerry Hensley

    1
    This ultraviolet image of CW Leonis from NASA’s Galaxy Evolution Explorer spacecraft shows the remarkable shell surrounding the star. [NASA/JPL-Caltech]

    The sooty cloud surrounding the carbon star CW Leonis is known to contain more than 50 types of molecules, and the remaining unassigned spectral lines hint that many more molecules are present. Can a laboratory study of a metallic molecule help us identify some of these mystery spectral lines?

    Searching Space for Chemical Compounds

    2
    Another view of CW Leonis, this time from the Hubble Space Telescope. This image highlights the dusty layers shed by this evolved star. [T. Ueta, H. Kim/NASA ESA Hubble CC BY 4.0]

    Astronomers have discovered more than 200 molecules in space since the first molecule was found in 1937. These discoveries confirmed something incredible — that in the cold, sparse space environment, individual atoms can link up to form complex molecules. Finding molecules in space represents both a challenge and an opportunity: how can we explain the presence of molecules in such an unforgiving environment, and how can we use the fact that they do exist to learn about the chemistry of interstellar and circumstellar space?

    One of the best sites to study extraterrestrial molecules is in the dusty shroud and outflows of the star CW Leonis, also known as IRC+10216. CW Leonis is a carbon star: a supergiant star with a high abundance of carbon in its atmosphere. Among CW Leonis’s many molecules are metal-containing species like silicon dicarbide (SiC2), leading researchers to wonder if similar molecules might be responsible for any of the remaining unidentified lines in CW Leonis’s spectrum.

    Making Magnesium Molecules

    3
    Summary of the known transitions and energy levels for magnesium dicarbide, as determined from laboratory and astrophysical observations. [Changala et al. 2022]

    A team led by Bryan Changala‬ (Center for Astrophysics ∣ Harvard & Smithsonian) focused their search on magnesium dicarbide (MgC2). Changala and collaborators considered it likely that CW Leonis’s dusty shroud contains magnesium dicarbide because it’s chemically similar to the already-discovered silicon dicarbide, and many other magnesium-containing molecules have been found there.

    How do you determine if a star’s spectral lines are due to a particular molecule, though? In order to be confident that we’ve discovered a molecule in space, we need to know its spectrum, which is best determined by studying the molecule in a lab. In the case of magnesium dicarbide, researchers have used quantum mechanical models to predict the molecule’s spectrum but had never confirmed it in a lab.

    Changala‬ and coauthors combined magnesium atoms with acetylene molecules, which are made of carbon and hydrogen, hoping to synthesize magnesium dicarbide. The team successfully matched a spectral line from their sample to a line predicted by quantum mechanical models and performed additional tests to ensure that the molecule they created was actually magnesium dicarbide.

    Seeking a Spectral Match

    4
    Example of a spectral line attributed to magnesium dicarbide. The fitted line profile is shown in red, and the blue “U” indicates unidentified lines. [Adapted from Changala et al. 2022]

    Ultimately, Changala and collaborators used the spectrum of the newly synthesized molecule to assign 14 of CW Leonis’s unknown spectral lines to magnesium dicarbide and its isotopologues — molecules with the same chemical formula and structure in which one or more atoms has a different number of neutrons.

    What does the discovery of magnesium dicarbide in CW Leonis’s spectrum tell us? By comparing the abundance of magnesium dicarbide in the star’s surroundings with the abundances of other magnesium-containing molecules, researchers might be able to glean how these molecules are made. Additionally, these observations may help us understand how metals affect the chemistry of carbon-rich environments like the surroundings of carbon stars, helping to lift the veil on these dusty objects.

    Citation

    Laboratory and Astronomical Discovery of Magnesium Dicarbide, MgC2, P. B. Changala et al 2022 ApJL 940 L42.
    https://iopscience.iop.org/article/10.3847/2041-8213/aca144/pdf
    See the science paper for instructive material with images.

    See the full article here .

    Comments are invited and will be appreciated, especially if the reader finds any errors which I can correct. Use “Reply”.


    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.


    Stem Education Coalition

    1

    The mission of the American Astronomical Society is to enhance and share humanity’s scientific understanding of the Universe.

    The Society, through its publications, disseminates and archives the results of astronomical research. The Society also communicates and explains our understanding of the universe to the public.
    The Society facilitates and strengthens the interactions among members through professional meetings and other means. The Society supports member divisions representing specialized research and astronomical interests.
    The Society represents the goals of its community of members to the nation and the world. The Society also works with other scientific and educational societies to promote the advancement of science.
    The Society, through its members, trains, mentors and supports the next generation of astronomers. The Society supports and promotes increased participation of historically underrepresented groups in astronomy.
    The Society assists its members to develop their skills in the fields of education and public outreach at all levels. The Society promotes broad interest in astronomy, which enhances science literacy and leads many to careers in science and engineering.

    Adopted June 7, 2009

    The society was founded in 1899 through the efforts of George Ellery Hale. The constitution of the group was written by Hale, George Comstock, Edward Morley, Simon Newcomb and Edward Charles Pickering. These men, plus four others, were the first Executive Council of the society; Newcomb was the first president. The initial membership was 114. The AAS name of the society was not finally decided until 1915, previously it was the “Astronomical and Astrophysical Society of America”. One proposed name that preceded this interim name was “American Astrophysical Society”.

    The AAS today has over 7,000 members and six divisions – the Division for Planetary Sciences (1968); the Division on Dynamical Astronomy (1969); the High Energy Astrophysics Division (1969); the Solar Physics Division (1969); the Historical Astronomy Division (1980); and the Laboratory Astrophysics Division (2012). The membership includes physicists, mathematicians, geologists, engineers and others whose research interests lie within the broad spectrum of subjects now comprising contemporary astronomy.

    In 2019 three AAS members were selected into the tenth anniversary class of TED Fellows.

    The AAS established the AAS Fellows program in 2019 to “confer recognition upon AAS members for achievement and extraordinary service to the field of astronomy and the American Astronomical Society.” The inaugural class was designated by the AAS Board of Trustees and includes an initial group of 232 Legacy Fellows.

     
  • richardmitnick 10:28 pm on December 17, 2022 Permalink | Reply
    Tags: "Finding Ways to Catch Collapsars Making Heavy Metals", "r-process", AAS NOVA, , , , ,   

    From AAS NOVA: “Finding Ways to Catch Collapsars Making Heavy Metals” 

    AASNOVA

    From AAS NOVA

    12.14.22
    Kerry Hensley

    1
    An artist’s impression of a collapsar and an associated gamma-ray burst. [NASA/SkyWorks Digital]

    Researchers are still working out where heavy metals are made in the universe. A recent publication explores ways to tell if elements heavier than iron can be created when extremely massive stars collapse to form black holes.

    Making Heavy Metals

    In the cores of stars, nuclear fusion combines light elements into heavier ones, with the largest stars generating elements up to iron. But elements bulkier than iron must arise elsewhere, since a star that attempts to create anything heavier is doomed to collapse in a supernova explosion.

    About half of the elements beyond iron on the periodic table are thought to form through something called the r-process, in which atoms rapidly capture multiple neutrons in a dense, hot environment. Core-collapse supernovae were early contenders for r-process production, but simultaneous observations of light and gravitational waves from colliding neutron stars cemented mergers as an important source of heavy elements. Now, researchers are searching for ways to determine if certain supernovae could be sites of r-process element creation after all.

    Collapsars as Candidates

    Collapsars are rapidly rotating massive stars that explode as supernovae when they can no longer sustain nuclear fusion, ultimately creating a black hole. As the star’s core collapses, material in the outer layers forms an accretion disk, in which conditions for r-process element formation may exist. To probe the possible role that collapsars play in generating r-process elements, Jennifer Barnes (University of California-Santa Barbara) and Brian Metzger (Columbia University and Flatiron Institute) modeled the effects of r-process nucleosythesis on the light curves of collapsars exploding as supernovae.

    2
    An illustration of the authors’ model, in which r-process-enriched material is surrounded by an r-process-poor shell. [Barnes & Metzger 2022]

    Barnes and Metzger first used an analytical model to predict when the presence of r-process products might be observable as the supernova’s emission rises and falls, as well as how best to observe these effects. The team found that it may be possible to discern whether a collapsar explosion contains r-process material by making long-wavelength observations several months after the explosion, depending on how the material is distributed, but early in the explosion might offer a better chance of identifying these events.

    Light Curve Modeling

    As a follow-on to their initial investigation, the team modeled the evolution of light curves from collapsar explosions that produce varying amounts of r-process material. These models explore how supernova light curves change as a function of the mass ejected in the explosion, the velocity of the ejected mass, the amount of nickel-56 (a radioactive form of nickel that decays into cobalt-56, creating the characteristic shape of many supernova light curves), and the amount and distribution of r-process material.

    3
    Demonstration of how the degree of mixing (ψmix) affects the resultant light curve. As the degree of mixing increases (higher ψmix), the emission shifts toward the near-infrared. [Barnes & Metzger 2022]

    In general, the presence of r-process material causes supernova light curves to shift toward redder frequencies, though the distribution of the material plays a large role in how visible this effect is; material concentrated at the center of the explosion will have little effect, while material mixed throughout will have a larger effect. Ultimately, the authors concluded that monitoring supernovae for ~75 days after they explode could be a viable way to identify collapsars that produce r-process elements, paving the way for near-infrared follow-up observations with Webb.

    Citation

    Signatures of r-process Enrichment in Supernovae from Collapsars, Jennifer Barnes and Brian D. Metzger 2022 ApJL 939 L29.
    https://iopscience.iop.org/article/10.3847/2041-8213/ac9b41/pdf
    See the science paper for instructive material with images.

    See the full article here .

    Comments are invited and will be appreciated, especially if the reader finds any errors which I can correct. Use “Reply”.


    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.


    Stem Education Coalition

    1

    The mission of the American Astronomical Society is to enhance and share humanity’s scientific understanding of the Universe.

    The Society, through its publications, disseminates and archives the results of astronomical research. The Society also communicates and explains our understanding of the universe to the public.
    The Society facilitates and strengthens the interactions among members through professional meetings and other means. The Society supports member divisions representing specialized research and astronomical interests.
    The Society represents the goals of its community of members to the nation and the world. The Society also works with other scientific and educational societies to promote the advancement of science.
    The Society, through its members, trains, mentors and supports the next generation of astronomers. The Society supports and promotes increased participation of historically underrepresented groups in astronomy.
    The Society assists its members to develop their skills in the fields of education and public outreach at all levels. The Society promotes broad interest in astronomy, which enhances science literacy and leads many to careers in science and engineering.

    Adopted June 7, 2009

    The society was founded in 1899 through the efforts of George Ellery Hale. The constitution of the group was written by Hale, George Comstock, Edward Morley, Simon Newcomb and Edward Charles Pickering. These men, plus four others, were the first Executive Council of the society; Newcomb was the first president. The initial membership was 114. The AAS name of the society was not finally decided until 1915, previously it was the “Astronomical and Astrophysical Society of America”. One proposed name that preceded this interim name was “American Astrophysical Society”.

    The AAS today has over 7,000 members and six divisions – the Division for Planetary Sciences (1968); the Division on Dynamical Astronomy (1969); the High Energy Astrophysics Division (1969); the Solar Physics Division (1969); the Historical Astronomy Division (1980); and the Laboratory Astrophysics Division (2012). The membership includes physicists, mathematicians, geologists, engineers and others whose research interests lie within the broad spectrum of subjects now comprising contemporary astronomy.

    In 2019 three AAS members were selected into the tenth anniversary class of TED Fellows.

    The AAS established the AAS Fellows program in 2019 to “confer recognition upon AAS members for achievement and extraordinary service to the field of astronomy and the American Astronomical Society.” The inaugural class was designated by the AAS Board of Trustees and includes an initial group of 232 Legacy Fellows.

     
  • richardmitnick 10:52 am on December 11, 2022 Permalink | Reply
    Tags: "Dotting the i’s and Crossing the t’s - Follow-Up of an Exo-Venus", "TSM": Transmission Spectroscopy Metric, AAS NOVA, An exoplanet circling GJ 3929, , , , , , ,   

    From AAS NOVA: “Dotting the i’s and Crossing the t’s – Follow-Up of an Exo-Venus” 

    AASNOVA

    From AAS NOVA

    12.9.22
    Ben Cassese

    1
    An artist’s impression of a small exoplanet. [T. Pyle, CC BY 4.0/NASA Ames/JPL-Caltech/]

    Initial discovery is one thing, but true knowledge of a new exoplanet system requires careful follow-up studies. Sometimes, this extra effort simply refines what astronomers had already inferred; other times, it can turn up a surprise. In the best cases, such as a recent study focused on a planet circling GJ 3929, it can do both.

    Suggestions of a Planet

    It all started with the Transiting Exoplanet Survey Satellite (TESS), NASA’s latest planet-hunting lookout.

    ___________________________________________________________________
    National Aeronautics Space Agency/Massachusetts Institute of Technology TESS

    NASA/MIT Tess in the building.

    National Aeronautics Space Agency/Massachusetts Institute of Technology TESS – Transiting Exoplanet Survey Satellite replaced the Kepler Space Telescope in search for exoplanets. TESS is a NASA Astrophysics Explorer mission led and operated by Massachusetts Institute of Technology, and managed by NASA’s Goddard Space Flight Center.


    The NASA Goddard Space Flight Center

    Additional partners include Northrop Grumman, based in Falls Church, Virginia; NASA’s Ames Research Center in California’s Silicon Valley; the Center for Astrophysics – Harvard and Smithsonian; MIT Lincoln Laboratory; and the NASA Space Telescope Science Institute in Baltimore.


    ___________________________________________________________________
    Over its now four years in orbit, TESS has stared at millions of stars, checking each for signs of any attendant planets buzzing nearby. While TESS has been great at its job, it’s more of a scout for the exoplanet community than a detective: with so much sky to search, this busy satellite usually watches a star for only a few days at a time before moving on, alerting astronomers when it sees something suspicious but leaving the confirmation to others.

    TESS phoned home to report on one of these candidate planets, GJ 3929b, in May of 2020. This one caught the eye of several teams long accustomed to scanning TESS reports: if this one was real, it was interesting. Although it was purportedly similar in size to Earth, it whipped around its tiny host star once every two days, making our languid year-long trip around the Sun seem lazy.

    Earlier in 2022, another team published their analysis of GJ 3929b, which confirmed it was indeed an exo-Venus, and which hinted at a possible second, slightly farther out planetary companion. Recently, a team led by Corey Beard (University of California-Irvine) revealed their own exhaustive analysis, which went a step further and confirmed the second planet.

    Many Methods

    2
    The best-fitting model of the radial velocity of GJ 3929, with data collected from multiple telescopes overplotted.

    The long-period component is from the newly confirmed planet c, while the faster sinusoid marks the influence of the inner planet b. [Beard et al. 2022]

    To both refine the initial measurements TESS sent back and to search for other planets hiding nearby, Beard and collaborators employed an entire flotilla of telescopes.



    Each of which was tasked with gathering some new type of information: some took high-resolution images to search for nearby dim red stars which TESS missed, some acquired diagnostic spectra of the host star, and others recorded additional transits of the initial planet.

    The centerpiece of their analysis, however, turned on a particularly powerful new tool: the NEID (rhymes with “fluid,” from the Tohono O’odham word meaning “to see”) spectrometer at the Kitt Peak National Observatory.

    With a spectral resolution of R=110,000 and the ability to detect changes in the star’s motion down to 1.18 m/s, the team not only pinned down the mass of GJ 3929b, they also confirmed that GJ 3929c really was another planet circling a bit farther out on an a 15-day orbit.

    A Special Planet

    3
    A scatterplot showing how amicable planets of different radii are to atmosphere characterization (Transmission Spectroscopy Metric (TSM)). GJ 3929b, the main focus of this work, is shown in blue: it is one of the most promising known small planets for future atmospheric studies. [Beard et al. 2022]

    Every newly discovered planet is equally special, but in the era of Webb, some are more equal than others. That’s because Webb has a preference for puffy planetary atmospheres around puny stars: that’s the combination which is easiest for it to sniff out different molecules floating in the exoplanet’s air. Excitingly, Beard and collaborators showed that if GJ 3929 has an atmosphere, it’s likely perfect for this type of follow up. So, perhaps in a few years, we’ll see more follow-up of this system, but this time from another space-based informant.

    Citation

    “GJ 3929: High-precision Photometric and Doppler Characterization of an Exo-Venus and Its Hot, Mini-Neptune-mass Companion,” Corey Beard et al 2022 ApJ 936 55.
    https://iopscience.iop.org/article/10.3847/1538-4357/ac8480
    See the science paper for instructive material with images.

    See the full article here .

    Comments are invited and will be appreciated, especially if the reader finds any errors which I can correct. Use “Reply”.


    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.


    Stem Education Coalition

    1

    The mission of the American Astronomical Society is to enhance and share humanity’s scientific understanding of the Universe.

    The Society, through its publications, disseminates and archives the results of astronomical research. The Society also communicates and explains our understanding of the universe to the public.
    The Society facilitates and strengthens the interactions among members through professional meetings and other means. The Society supports member divisions representing specialized research and astronomical interests.
    The Society represents the goals of its community of members to the nation and the world. The Society also works with other scientific and educational societies to promote the advancement of science.
    The Society, through its members, trains, mentors and supports the next generation of astronomers. The Society supports and promotes increased participation of historically underrepresented groups in astronomy.
    The Society assists its members to develop their skills in the fields of education and public outreach at all levels. The Society promotes broad interest in astronomy, which enhances science literacy and leads many to careers in science and engineering.

    Adopted June 7, 2009

    The society was founded in 1899 through the efforts of George Ellery Hale. The constitution of the group was written by Hale, George Comstock, Edward Morley, Simon Newcomb and Edward Charles Pickering. These men, plus four others, were the first Executive Council of the society; Newcomb was the first president. The initial membership was 114. The AAS name of the society was not finally decided until 1915, previously it was the “Astronomical and Astrophysical Society of America”. One proposed name that preceded this interim name was “American Astrophysical Society”.

    The AAS today has over 7,000 members and six divisions – the Division for Planetary Sciences (1968); the Division on Dynamical Astronomy (1969); the High Energy Astrophysics Division (1969); the Solar Physics Division (1969); the Historical Astronomy Division (1980); and the Laboratory Astrophysics Division (2012). The membership includes physicists, mathematicians, geologists, engineers and others whose research interests lie within the broad spectrum of subjects now comprising contemporary astronomy.

    In 2019 three AAS members were selected into the tenth anniversary class of TED Fellows.

    The AAS established the AAS Fellows program in 2019 to “confer recognition upon AAS members for achievement and extraordinary service to the field of astronomy and the American Astronomical Society.” The inaugural class was designated by the AAS Board of Trustees and includes an initial group of 232 Legacy Fellows.

     
  • richardmitnick 12:02 pm on December 3, 2022 Permalink | Reply
    Tags: "Sizing Up Galaxies at Cosmic Noon", AAS NOVA, , , , , , ,   

    From AAS NOVA: “Sizing Up Galaxies at Cosmic Noon” 

    AASNOVA

    From AAS NOVA

    12.2.22
    Kerry Hensley

    1
    Image of Cosmic Evolution Early Release Science scientists looking at the Epoch 1 Near-Infrared Camera color mosaic in the Texas Advanced Computing Center’s visualization lab at University of Texas at Austin. Credit: R. Larson.

    How do galaxies grow? It’s a simple question, but answering it is complicated. A recent publication suggests that Webb observations might upend what we think we know about galaxy growth.

    Evolution Seen from Afar

    2
    Comparison of Hubble (left) and Webb (right) images of the Pillars of Creation. The different wavelength ranges spanned by Hubble and Webb have the potential to illuminate different aspects of many cosmic settings. [Science: NASA, ESA, CSA, STScI, Hubble Heritage Project (STScI, AURA); Image processing: Joseph DePasquale (STScI), Anton M. Koekemoer (STScI), Alyssa Pagan (STScI)]

    From our vantage point in the local universe, it’s hard to tell how the galaxies we see today evolved into their current forms.

    To understand how galaxies grow, we need high-resolution observations of galaxies billions of light-years away, and a succession of increasingly precise space telescopes have made these measurements possible.

    Observations with the Hubble Space Telescope helped establish some fundamental rules of galaxy growth: galaxies were smaller in the past than they are today, galaxies that are more massive are usually larger, and galaxies that are actively forming stars are larger than those that are not. But constraints set by Hubble’s observing wavelength range might mean that these rules are due for a reassessment, and Webb is poised to put them to the test.

    Webb Enters the Scene

    When Hubble observes galaxies in the early universe, it’s seeing light emitted at optical and ultraviolet wavelengths, while Webb sees light that originated in the near-infrared. This small difference might have a big impact: near-infrared light is a better tracer of stellar mass than optical or ultraviolet light, and it’s less sensitive to spatial changes in the mass-to-light ratio seen in some galaxies. Ultimately, when combined with its exceptional resolution, this means that Webb should provide more reliable measurements of galaxy sizes than other telescopes.

    Using data from the Webb Cosmic Evolution Early Release Science (CEERS) program, Katherine Suess (University of California-Santa Cruz and Stanford University) and collaborators studied galaxies during an era commonly nicknamed cosmic noon, which is marked by an abundance of star formation. The team’s goal was to determine the sizes of galaxies during this epoch at two different wavelengths (1.5 and 4.4 microns; 1 micron = 10^-6 meter) that correspond to light emitted in the optical and near-infrared, respectively.

    3
    The galaxies surveyed are situated in the Extended Groth Strip, which was previously observed by Hubble. Click to enlarge. [M. Davis (University of California-Berkeley)/NASA, ESA.

    How Do They Measure Up?

    4
    Comparison of galaxy sizes in 4.4-micron Webb images to 1.5-micron Webb images. [Suess et al. 2022]

    Suess and coauthors selected 1,179 bright galaxies with redshift, z, between 1.0 and 2.5 and used a computer algorithm to measure the sizes of these galaxies in the 1.5- and 4.4-micron Webb images. For the 703 galaxies successfully fit by this method, there was a definite size difference between the two wavelengths: the galaxies were, on average, 9% smaller in the 4.4-micron images than in the 1.5-micron images. This means that galaxies are more compact than rest-frame optical observations (e.g., Hubble observations) would suggest. Intriguingly, the difference in size between the two wavelengths appears to be a function of galaxy mass and color — the lightest, bluest galaxies surveyed scarcely show a size change, while those that are redder and more massive show a 30% size decrement at the longer wavelength.

    This seemingly straightforward finding might play a role in rewriting the rules of galaxy evolution. For instance, the mass-dependent size decrease between the 1.5- and 4.4-micron images might mean that massive galaxies aren’t actually much larger than their lighter counterparts! While the authors stress that there’s more analysis to be done, it’s clear that Webb observations will have an outsize impact on our understanding of galaxy growth.

    Citation

    Rest-frame Near-infrared Sizes of Galaxies at Cosmic Noon: Objects in JWST’s Mirror Are Smaller than They Appeared, Katherine A. Suess et al. 2022 ApJL 937 L33.
    https://iopscience.iop.org/article/10.3847/2041-8213/ac8e06/pdf
    See the science paper for instructive material with images and tables.

    See the full article here .

    Comments are invited and will be appreciated, especially if the reader finds any errors which I can correct. Use “Reply”.


    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.


    Stem Education Coalition

    1

    The mission of the American Astronomical Society is to enhance and share humanity’s scientific understanding of the Universe.

    The Society, through its publications, disseminates and archives the results of astronomical research. The Society also communicates and explains our understanding of the universe to the public.
    The Society facilitates and strengthens the interactions among members through professional meetings and other means. The Society supports member divisions representing specialized research and astronomical interests.
    The Society represents the goals of its community of members to the nation and the world. The Society also works with other scientific and educational societies to promote the advancement of science.
    The Society, through its members, trains, mentors and supports the next generation of astronomers. The Society supports and promotes increased participation of historically underrepresented groups in astronomy.
    The Society assists its members to develop their skills in the fields of education and public outreach at all levels. The Society promotes broad interest in astronomy, which enhances science literacy and leads many to careers in science and engineering.

    Adopted June 7, 2009

    The society was founded in 1899 through the efforts of George Ellery Hale. The constitution of the group was written by Hale, George Comstock, Edward Morley, Simon Newcomb and Edward Charles Pickering. These men, plus four others, were the first Executive Council of the society; Newcomb was the first president. The initial membership was 114. The AAS name of the society was not finally decided until 1915, previously it was the “Astronomical and Astrophysical Society of America”. One proposed name that preceded this interim name was “American Astrophysical Society”.

    The AAS today has over 7,000 members and six divisions – the Division for Planetary Sciences (1968); the Division on Dynamical Astronomy (1969); the High Energy Astrophysics Division (1969); the Solar Physics Division (1969); the Historical Astronomy Division (1980); and the Laboratory Astrophysics Division (2012). The membership includes physicists, mathematicians, geologists, engineers and others whose research interests lie within the broad spectrum of subjects now comprising contemporary astronomy.

    In 2019 three AAS members were selected into the tenth anniversary class of TED Fellows.

    The AAS established the AAS Fellows program in 2019 to “confer recognition upon AAS members for achievement and extraordinary service to the field of astronomy and the American Astronomical Society.” The inaugural class was designated by the AAS Board of Trustees and includes an initial group of 232 Legacy Fellows.

     
  • richardmitnick 5:25 pm on December 2, 2022 Permalink | Reply
    Tags: "Four Stars - Many Eclipses", AAS NOVA, , , , , ,   

    From AAS NOVA: “Four Stars – Many Eclipses” 

    AASNOVA

    From AAS NOVA

    11.23.22
    Ben Cassese

    1
    An image of nearby stars, although not bound together like TIC 114936199. [J. Kalirai, CC BY 4.0/ NASA/ESA Hubble]

    There are light curves, then there are light curves. Recently, astronomers untangled a particularly complex signal and revealed its surprisingly elegant cause: not one, two, or even three, but four stars locked into a never-ending dance.

    A Mystery Light Curve

    Over the past 20 years, astronomers have piled up quite the hoard of stellar light curves. Most of these are predictable, fairly simple time series: sure, the brightness of a given star might oscillate pseudo-regularly around its average as star spots come and go or the star shrinks and swells, but by and large, most curves don’t reveal anything surprising. A handful of exciting curves shelter the telltale signature of a transiting planet. Another handful hosts the unfortunately similar signature of eclipsing binary stars. Almost all of them can be explained by fairly simple models, just one or two stars and their planets going about their usual lives.

    2
    Measurements of TIC 114936199’s brightness over time, as observed in three different TESS sectors. Note the changes to the y-axis scale after the first sector. [Powell et al. 2022]

    However, a few light curves among the hundreds of thousands recorded so far are bafflingly weird. Take the measurements of the source named TIC 114936199, which the Transiting Exoplanet Survey Satellite (TESS) watched in three disconnected chunks of about 30 days.

    The second and third of these chunks look like a standard eclipsing binary. But that first stare… What could cause such deep, non-repeating dips?

    To find out, a team led by Brian Powell (NASA Goddard Space Flight Center) started looking into arrangements of more and more eclipsing stars to explain how nature could create such strange dips in the first sector but not the others. A few clues led them to consider assemblages of four stars, which had been spotted by TESS before. But actually describing the size, location, and velocities of those four stars proved quite the challenge.

    3
    A cartoon illustration of TIC 114936199’s components: four stars all bound together. The deep eclipses were the result of stars Aa and Ab passing in front of star C at the same time. [Powell et al. 2022]

    Wandering the landscape of such a broad parameter space, Powell and collaborators found that standard Monte Carlo fitting routines got lost in the hills of local minima and could not find a reasonable solution. The team first increased their computational firepower by switching to a NASA supercomputer, then they deployed other algorithms such as Particle Swarm Optimization and Differential Evolution. In this exploration phase, the team churned through millions of possible combinations over many hundreds of thousands of computing hours.

    All of this effort got them within the ballpark of a reasonable solution, and when they sensed they were close, the team again unleashed their fitting algorithm. This time, it made a beeline for their final solution, a configuration of four stars circling three different centers.

    Successful Solution

    5
    A zoom-in of data from the first TESS sector (blue) compared with the final model (red line). The residuals are shown below the time series. [Powell et al. 2022]

    The model precisely predicted every one of the many dips in the intricate pattern in the first TESS sector, and it successfully explained why the pattern did not repeat: the innermost stars, Aa and Ab, eclipse each other every 3 days, but for 12 days in that first sector, they both also occasionally eclipsed star C as it drifted through the background. That particular arrangement should happen again in 2025, but after that we’ll have to wait much longer for the next lineup in 2071. While this isn’t the first quadruple star system observed by TESS, it is the first in this 2+1+1 configuration. Hopefully, astronomers will be able to observe the next series of complex eclipses in three years’ time — if not, they’ll have to wait a half century before enjoying such a dramatic show again.

    Citation

    “TIC 114936199: A Quadruple Star System with a 12 Day Outer-orbit Eclipse,” Brian P. Powell et al 2022 ApJ. 938 133.
    https://iopscience.iop.org/article/10.3847/1538-4357/ac8934/pdf
    See the science paper for instructive material with images.

    See the full article here .

    Comments are invited and will be appreciated, especially if the reader finds any errors which I can correct. Use “Reply”.


    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.


    Stem Education Coalition

    1

    The mission of the American Astronomical Society is to enhance and share humanity’s scientific understanding of the Universe.

    The Society, through its publications, disseminates and archives the results of astronomical research. The Society also communicates and explains our understanding of the universe to the public.
    The Society facilitates and strengthens the interactions among members through professional meetings and other means. The Society supports member divisions representing specialized research and astronomical interests.
    The Society represents the goals of its community of members to the nation and the world. The Society also works with other scientific and educational societies to promote the advancement of science.
    The Society, through its members, trains, mentors and supports the next generation of astronomers. The Society supports and promotes increased participation of historically underrepresented groups in astronomy.
    The Society assists its members to develop their skills in the fields of education and public outreach at all levels. The Society promotes broad interest in astronomy, which enhances science literacy and leads many to careers in science and engineering.

    Adopted June 7, 2009

    The society was founded in 1899 through the efforts of George Ellery Hale. The constitution of the group was written by Hale, George Comstock, Edward Morley, Simon Newcomb and Edward Charles Pickering. These men, plus four others, were the first Executive Council of the society; Newcomb was the first president. The initial membership was 114. The AAS name of the society was not finally decided until 1915, previously it was the “Astronomical and Astrophysical Society of America”. One proposed name that preceded this interim name was “American Astrophysical Society”.

    The AAS today has over 7,000 members and six divisions – the Division for Planetary Sciences (1968); the Division on Dynamical Astronomy (1969); the High Energy Astrophysics Division (1969); the Solar Physics Division (1969); the Historical Astronomy Division (1980); and the Laboratory Astrophysics Division (2012). The membership includes physicists, mathematicians, geologists, engineers and others whose research interests lie within the broad spectrum of subjects now comprising contemporary astronomy.

    In 2019 three AAS members were selected into the tenth anniversary class of TED Fellows.

    The AAS established the AAS Fellows program in 2019 to “confer recognition upon AAS members for achievement and extraordinary service to the field of astronomy and the American Astronomical Society.” The inaugural class was designated by the AAS Board of Trustees and includes an initial group of 232 Legacy Fellows.

     
  • richardmitnick 3:20 pm on November 30, 2022 Permalink | Reply
    Tags: "Four Perspectives on Neutron Stars and Pulsars and Magnetars", AAS NOVA, , , ,   

    From AAS NOVA: “Four Perspectives on Neutron Stars and Pulsars and Magnetars” 

    AASNOVA

    From AAS NOVA

    11.30.22
    Kerry Hensley

    1
    Illustration of a neutron star emitting a jet. [ICRAR/University of Amsterdam]

    When a massive star explodes as a supernova, its core collapses into a city-sized sphere of neutrons called a neutron star. These extraordinarily dense stars — just one teaspoon of a neutron star would weigh billions of tons in Earth’s gravity — exhibit some of the most intriguing behavior in the universe: rapid rotation, beams of radio emission, and extremely strong magnetic fields. Today, we’ll introduce four recent research articles that explore different aspects of these stars.

    Bursting, Cooling, and Bursting Again

    1
    Simulated light curves during an X-ray burst, showing the effects of incorporating different physics. A model without neutrino cooling (labeled “No DU” in reference to the neutrino cooling pathway called direct Urca), peaks at a lower luminosity than models incorporating neutrino cooling. [Adapted from Dohi et al. 2022]

    Sometimes, neutron stars reveal themselves by interacting with other stars. When a neutron star gathers gas from a stellar companion, the gas can ignite on the star’s scorching surface, resulting in a sudden burst of X-rays. After this sudden influx of heat, how does the neutron star cool, and how is the cooling reflected in the star’s light curve? While this may seem like a simple question, the answer hinges on our understanding of the conditions within the neutron star’s interior as well as the characteristics of the gas being accreted.

    In a recent publication, a team led by Akira Dohi (Kyushu University[土肥明] (JP)) explored the issue of neutron star cooling with general relativistic stellar evolution models. Specifically, the team investigated the effects of cooling by emitting neutrinos — chargeless, nearly massless particles that scarcely interact with matter — which is expected to speed up the cooling rate.

    The authors found that neutrino cooling increases the time between outbursts but makes them brighter at their peak, though additional physics to be included in future modeling might suppress this effect.

    3
    Simulated pulses showing a change in the phase of the pulse due to the shifting motion of the sparks. [Adapted from Basu et al. 2022]

    Simulating Pulsar Sparks

    Rahul Basu (University of Zielona Góra, Poland) and collaborators reported on simulations of conditions very close to the surface of a neutron star that emits beams of radio emission. Neutron stars that emit beamed radio waves are called pulsars for the way the beams sweep across our field of view, generating what we see as pulses of emission.

    Near a pulsar’s surface, extremely high temperatures and strong magnetic and electric fields combine forces to summon a sea of charged particles that are then accelerated to relativistic speeds.

    Basu and collaborators focused on a phenomenon called sparking, in which charged particles jump the gap between the pulsar’s surface at its poles and its plasma-rich magnetosphere. The team’s modeling demonstrated that a pulsar’s poles are tightly filled with constant sparks, and the arrangement of these sparks slowly shifts over time. By modeling the emission associated with the simulated sparks, the team showed that the shifting motion of the sparks appears to be responsible for the observed periodic variations in the phases and amplitudes of some pulsars’ pulses.

    Pulsars Probing Gravitational Waves

    4
    Example of a pulse observed with the Giant Metrewave Radio Telescope. [Adapted from Sharma et al. 2022]

    By studying large groups of pulsars, astronomers hope to learn about something seemingly unrelated: gravitational waves.

    Pulsars provide a method to detect gravitational waves by way of these stars’ impeccable timekeeping abilities — because a pulsar’s radio beat is so reliable, the slight distortion of space caused by a passing gravitational wave should impact the arrival times of a pulsar’s pulses.

    However, there’s a complication to this technique: spatial and temporal changes in the interstellar medium plasma can also affect when a pulsar’s radio pulses arrive at Earth. In order to compensate for the effect of the interstellar medium, we need to be able to make precise observations of pulsars across a range of radio frequencies. In a recent research article, Shyam Sharma (Tata Institute of Fundamental Research, India) and collaborators tested a pulsar-timing measurement technique using the Giant Metrewave Radio Telescope, which is highly sensitive to low-frequency radio waves. Sharma and coauthors showed that observing using a wide frequency band yields results comparable to typical narrowband observations, indicating that this technique could be used to disentangle the effects of the interstellar medium and more accurately time the pulses of arrays of pulsars, opening a new window onto gravitational waves.

    Magnetic Outbursts

    5
    Temperature maps of the top of a magnetar’s crust (top) and the magnetar’s surface (bottom) after a hotspot is injected. [De Grandis et al. 2022]

    As if neutron stars could get any wilder: some neutron stars, dubbed magnetars, have extremely strong magnetic fields and exhibit frequent X-ray flares. While the cause of these X-ray outbursts is still unknown, some researchers have suggested that they arise from a sudden upwelling of magnetic energy beneath the magnetar’s crust, creating a hot spot that cools gradually over days or months.

    To understand how the injection of heat into a magnetar’s crust might create the spectral features seen during X-ray outbursts, Davide De Grandis (University of Padova, Italy) and coauthors employed a three-dimensional magnetothermal model of hotspot formation and cooling. This model allowed the team to study the effects of asymmetrical hot spots under a magnetar’s crust for the first time. The team was able to confirm that these hot spots can be responsible for outbursts, though we’ll have to wait for future research to fully explore the evolution of the spectral features generated during these events.

    Citations

    “Impacts of the Direct Urca and Superfluidity inside a Neutron Star on Type I X-Ray Bursts and X-Ray Superbursts,” A. Dohi et al 2022 ApJ 937 124.
    https://iopscience.iop.org/article/10.3847/1538-4357/ac8dfe/pdf

    “Two-dimensional Configuration and Temporal Evolution of Spark Discharges in Pulsars,” Rahul Basu et al 2022 ApJ 936 35.
    https://iopscience.iop.org/article/10.3847/1538-4357/ac8479/pdf

    “Wide-band Timing of GMRT-discovered Millisecond Pulsars,” Shyam S. Sharma et al 2022 ApJ 936 86.
    https://iopscience.iop.org/article/10.3847/1538-4357/ac86d8/pdf

    “Three-dimensional Magnetothermal Simulations of Magnetar Outbursts,” Davide De Grandis et al 2022 ApJ 936 99.
    https://iopscience.iop.org/article/10.3847/1538-4357/ac8797/pdf

    See the full article here .

    Comments are invited and will be appreciated, especially if the reader finds any errors which I can correct. Use “Reply”.


    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.


    Stem Education Coalition

    1

    The mission of the American Astronomical Society is to enhance and share humanity’s scientific understanding of the Universe.

    The Society, through its publications, disseminates and archives the results of astronomical research. The Society also communicates and explains our understanding of the universe to the public.
    The Society facilitates and strengthens the interactions among members through professional meetings and other means. The Society supports member divisions representing specialized research and astronomical interests.
    The Society represents the goals of its community of members to the nation and the world. The Society also works with other scientific and educational societies to promote the advancement of science.
    The Society, through its members, trains, mentors and supports the next generation of astronomers. The Society supports and promotes increased participation of historically underrepresented groups in astronomy.
    The Society assists its members to develop their skills in the fields of education and public outreach at all levels. The Society promotes broad interest in astronomy, which enhances science literacy and leads many to careers in science and engineering.

    Adopted June 7, 2009

    The society was founded in 1899 through the efforts of George Ellery Hale. The constitution of the group was written by Hale, George Comstock, Edward Morley, Simon Newcomb and Edward Charles Pickering. These men, plus four others, were the first Executive Council of the society; Newcomb was the first president. The initial membership was 114. The AAS name of the society was not finally decided until 1915, previously it was the “Astronomical and Astrophysical Society of America”. One proposed name that preceded this interim name was “American Astrophysical Society”.

    The AAS today has over 7,000 members and six divisions – the Division for Planetary Sciences (1968); the Division on Dynamical Astronomy (1969); the High Energy Astrophysics Division (1969); the Solar Physics Division (1969); the Historical Astronomy Division (1980); and the Laboratory Astrophysics Division (2012). The membership includes physicists, mathematicians, geologists, engineers and others whose research interests lie within the broad spectrum of subjects now comprising contemporary astronomy.

    In 2019 three AAS members were selected into the tenth anniversary class of TED Fellows.

    The AAS established the AAS Fellows program in 2019 to “confer recognition upon AAS members for achievement and extraordinary service to the field of astronomy and the American Astronomical Society.” The inaugural class was designated by the AAS Board of Trustees and includes an initial group of 232 Legacy Fellows.

     
  • richardmitnick 5:26 pm on November 22, 2022 Permalink | Reply
    Tags: , AAS NOVA, , , , ,   

    From Astrobites Via AAS NOVA: “A Beginner’s Guide to Predicting Supernovae” 

    Astrobites bloc

    From Astrobites

    Via

    AASNOVA

    AAS NOVA

    11.22.22

    1
    This composite Hubble Space Telescope and Chandra X-ray Observatory image captures the visible, ultraviolet, and X-ray emission from Eta Carinae, which may contain the next star to go supernova in our galaxy. Updated neutrino detectors may be able to give us a few hours’ notice before Eta Carinae or similar stars go supernova. [NASA/CXC; Ultraviolet/Optical: NASA/STScI; Combined Image: NASA/ESA/N. Smith (University of Arizona), J. Morse (BoldlyGo Institute) and A. Pagan]

    Title: Pre-Supernova Alert System for Super-Kamiokande
    Authors: The Super-Kamiokande Collaboration
    First Author’s Institution: Institutions affiliated with the Super-Kamiokande Collaboration
    Status: Published in ApJ

    Let me start with a fun fact that you might have heard before: there are literally trillions of neutrinos flying through you every second while you are reading this.

    You might have noticed that you don’t feel these neutrinos at all (see also this article). It gets really weird knowing that most neutrinos casually fly through Earth without noticing the thousands of kilometers of planet they are passing through, and it’s even weirder to consider that these particles were only first detected in the 1950s.

    This immediately shows the problem with neutrinos: they really don’t like to talk to us. In a more scientifically correct way, we can say that neutrinos are weakly interacting. In fact, the only forces that have any sway on them are gravity and the weak force, the weakest of the four fundamental forces of nature. Of course, this doesn’t stop physicists from looking for neutrinos anyway. To do so, researchers build huge detectors, usually deep underground to shield the detectors from other cosmic radiation.

    _____________________________________________________
    U Wisconsin IceCube Neutrino Observatory

    U Wisconsin IceCube Neutrino Observatory neutrino detector at the at the Amundsen-Scott South Pole Station in Antarctica South Pole, elevation of 2,835 metres (9,301 feet).
    IceCube employs more than 5000 detectors lowered on 86 strings into almost 100 holes in the Antarctic ice NSF B. Gudbjartsson, IceCube Collaboration.

    Lunar Icecube

    IceCube Gen-2 DeepCore PINGU annotated

    IceCube neutrino detector interior.

    IceCube DeepCore annotated.

    DM-Ice II at IceCube annotated.


    _____________________________________________________
    Fermilab LBNF/DUNE Neutrino Experiment




    __________________________________________________
    These detectors are typically, although not always, filled with thousands of metric tons of heavy water that is surrounded by tens of thousands of light detectors in order to have a chance of seeing a few neutrinos.

    Now, how does a large pool of heavy water (no, you can’t swim in it) and a bunch of extremely sensitive light sensors help us detect a particle that doesn’t even care about an entire planet of material? This astrobite explains it swimmingly (pun intended). In short, neutrinos can only interact on very short distances and mainly do so with neutrons, so a good detector contains a large number of neutrons. We can provide an abundance of neutrons by either using a very dense material that naturally increases the amount of neutrons per volume, or by using materials that have more neutrons per atom. Heavy water fulfills the latter requirement. The light emitted by a neutrino interacting with a neutron is then seen by the light detectors, helping us find our neutrinos. Or at least a few of them — most still just fly through the detector without doing anything.

    Take It with a Grain of Gadolinium

    Today’s article discusses an improvement made to the Super-Kamiokande detector and how that improvement helps astronomers predict when a supernova might occur.

    In 2020, researchers added some 13 tons of gadolinium sulfate octahydrate to the water of the detector. Of course, they didn’t just add tons of a random molecule — gadolinium is around 100,000 times more likely to interact with neutrinos than hydrogen. Overall, this addition helps the the detector capture twice as many neutrinos as well as harder-to-detect low-energy neutrinos.

    It is exactly these lower-energy neutrinos that are relevant to predicting supernovae. In the cores of stars that are expected to go supernova, more and more violent nuclear reactions occur as the star approaches its end. In these last moments, just hours before the supernova, silicon atoms start to fuse and neutrinos are emitted as a result. With tons of new gadolinium molecules in the Super-Kamiokande detector, some of the neutrinos from this silicon fusion could be detected. For a well-known star like Betelgeuse, the silicon fusion would start about 10 hours before the star goes supernova. This would give astronomers an extra 10-hour warning, allowing them time to point every telescope and detector they can get their hands on towards the supernova candidate. The authors of today’s article predict how we would see these neutrinos coming in, shown in Figure 1.

    2

    Figure 1: Predicted number of neutrino detections in the Super-Kamiokande detector (y axis) per neutrino energy (x axis) in mega electron volts (MeV). The prediction is based on calculations with a Betelgeuse-like star and the neutrinos are expected to come mainly from silicon fusion adding up in the last 10 hours of the star’s life. The different colors highlight the different simulations used, while the full and dashed lines show the neutrinos expected from normal (NO) and inverted (IO) mass ordering, respectively. [Super-Kamiokande Collaboration 2022]
    How sensitive the Super-Kamiokande detector is to these neutrinos depends on a number of things:

    The star’s mass: Less-massive stars have a lower probability of emitting detectable neutrinos, simply because they will emit fewer neutrinos overall.
    The distance to the star: The detectable neutrinos are less likely to be observed if the star is farther away because the neutrinos are spread farther apart.
    Evolution of the star: Stars live their lives in very different ways. For example, stars with more metals will behave differently, which influences when and how many detectable neutrinos they will spew out.
    Neutrino mass ordering: Neutrino masses aren’t well constrained, since we have no reliable measurements of their masses. It is even uncertain which neutrino flavors have more or less mass, so the authors assume a normal and an inverse mass ordering based on these different neutrinos (see also Figure 1).

    The detector’s sensitivity could also be increased considerably by adding more of the gadolinium molecule to the detector’s water.

    All in all, the authors are fairly confident that the Super-Kamiokande detector can tell them whether a star up to nearly 2,000 light-years away from Earth will go supernova, giving us a warning several hours before the star finally and spectacularly kicks the bucket.

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.


    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.

     
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