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  • richardmitnick 1:35 pm on June 21, 2018 Permalink | Reply
    Tags: , , , NASA ESA Hubble, The nearby galaxy ESO 325-G004   

    From NASA/ESA Hubble Telescope and ESO VLT: “Most Precise Test of Einstein’s General Relativity Outside Milky Way” 

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    From NASA/ESA Hubble Telescope

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    From European Southern Observatory

    ESO VLT Platform at Cerro Paranal elevation 2,635 m (8,645 ft)

    6.21.18

    Thomas Collett
    University of Portsmouth
    Portsmouth, UK
    Tel: +44 239 284 5146
    Email: thomas.collett@port.ac.uk

    Bob Nichol
    University of Portsmouth
    Portsmouth, UK
    Tel: +44 239 284 3117
    Email: bob.nichol@port.ac.uk

    Mathias Jäger
    ESA/Hubble, Public Information Officer
    Garching bei München, Germany
    Tel: +49 176 62397500
    Email: mjaeger@partner.eso.org

    Richard Hook
    ESO Public Information Officer
    Garching bei München, Germany
    Tel: +49 89 3200 6655
    Cell: +49 151 1537 3591
    Email: pio@eso.org

    1

    An international team of astronomers using the NASA/ESA Hubble Space Telescope and the European Southern Observatory’s Very Large Telescope has made the most precise test of general relativity yet outside our Milky Way. The nearby galaxy ESO 325-G004 acts as a strong gravitational lens, distorting light from a distant galaxy behind it to create an Einstein ring around its centre. By comparing the mass of ESO 325-G004 with the curvature of space around it, the astronomers found that gravity on these astronomical length-scales behaves as predicted by general relativity. This rules out some alternative theories of gravity.

    Using the NASA/ESA Hubble Space Telescope and European Southern Observatory’s Very Large Telescope (VLT), a team led by Thomas Collett (University of Portsmouth, UK), was able to perform the most precise test of general relativity outside the Milky Way to date.

    The theory of general relativity predicts that objects deform spacetime, causing any light that passes by to be deflected and resulting in a phenomenon known as gravitational lensing. This effect is only noticeable for very massive objects. A few hundred strong gravitational lenses are known, but most are too distant to precisely measure their mass. However, the elliptical galaxy ESO 325-G004 is amongst the closest lenses at just 450 million light-years from Earth.

    Using the MUSE instrument on the VLT the team calculated the mass of ESO 325-G004 by measuring the movement of stars within it.

    ESO MUSE on the VLT

    Using Hubble the scientists were able to observe an Einstein ring resulting from light from a distant galaxy being distorted by the intervening ESO 325-G004. Studying the ring allowed the astronomers to measure how light, and therefore spacetime, is being distorted by the huge mass of ESO 325-G004.

    Collett comments: “We know the mass of the foreground galaxy from MUSE and we measured the amount of gravitational lensing we see from Hubble. We then compared these two ways to measure the strength of gravity — and the result was just what general relativity predicts, with an uncertainty of only nine percent. This is the most precise test of general relativity outside the Milky Way to date. And this using just one galaxy!”
    General relativity has been tested with exquisite accuracy on Solar System scales, and the motions of stars around the black hole at the centre of the Milky Way are under detailed study, but previously there had been no precise tests on larger astronomical scales. Testing the long range properties of gravity is vital to validate our current cosmological model.

    These findings may have important implications for models of gravity alternative to general relativity. These alternative theories predict that the effects of gravity on the curvature of spacetime are “scale dependent”. This means that gravity should behave differently across astronomical length-scales from the way it behaves on the smaller scales of the Solar System. Collett and his team found that this is unlikely to be true unless these differences only occur on length scales larger than 6000 light-years.

    “The Universe is an amazing place providing such lenses which we can use as our laboratories,” adds team member Bob Nichol (University of Portsmouth). “It is so satisfying to use the best telescopes in the world to challenge Einstein, only to find out how right he was.”

    The Hubble Space Telescope is a project of international cooperation between NASA and the European Space Agency. NASA’s Goddard Space Flight Center manages the telescope. The Space Telescope Science Institute (STScI), is a free-standing science center, located on the campus of The Johns Hopkins University and operated by the Association of Universities for Research in Astronomy (AURA) for NASA, conducts Hubble science operations.

    More information

    This research was presented in a paper entitled A precise extragalactic test of General Relativity by Collett et al., to appear in the journal Science.

    The team is composed of T. E. Collett (Institute of Cosmology and Gravitation, University of Portsmouth, Portsmouth, UK), L. J. Oldham (Institute of Astronomy, University of Cambridge, Cambridge, UK), R. Smith (Centre for Extragalactic Astronomy, Durham University, Durham, UK), M. W. Auger (Institute of Astronomy, University of Cambridge, Cambridge, UK), K. B. Westfall (Institute of Cosmology and Gravitation, University of Portsmouth, Portsmouth, UK; University of California Observatories – Lick Observatory, Santa Cruz, USA), D. Bacon (Institute of Cosmology and Gravitation, University of Portsmouth, Portsmouth, UK), R. C. Nichol (Institute of Cosmology and Gravitation, University of Portsmouth, Portsmouth, UK), K. L. Masters (Institute of Cosmology and Gravitation, University of Portsmouth, Portsmouth, UK), K. Koyama (Institute of Cosmology and Gravitation, University of Portsmouth, Portsmouth, UK), R. van den Bosch (Max Planck Institute for Astronomy, Königstuhl, Heidelberg, Germany).

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    ESO is the foremost intergovernmental astronomy organisation in Europe and the world’s most productive ground-based astronomical observatory by far. It is supported by 16 countries: Austria, Belgium, Brazil, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Poland, Portugal, Spain, Sweden, Switzerland and the United Kingdom, along with the host state of Chile. ESO carries out an ambitious programme focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries. ESO also plays a leading role in promoting and organising cooperation in astronomical research. ESO operates three unique world-class observing sites in Chile: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope, the world’s most advanced visible-light astronomical observatory and two survey telescopes. VISTA works in the infrared and is the world’s largest survey telescope and the VLT Survey Telescope is the largest telescope designed to exclusively survey the skies in visible light. ESO is a major partner in ALMA, the largest astronomical project in existence. And on Cerro Armazones, close to Paranal, ESO is building the 39-metre European Extremely Large Telescope, the E-ELT, which will become “the world’s biggest eye on the sky”.

    See the full NASA/ESA Hubble article here .
    See the full ESO/VLT article here .


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  • richardmitnick 10:12 am on May 31, 2018 Permalink | Reply
    Tags: , , , Cosmic collision lights up the darkness, , NASA ESA Hubble, NGC 3256-the site of a violent clash   

    From NASA/ESA Hubble Telescope: “Cosmic collision lights up the darkness” 

    NASA Hubble Banner

    NASA/ESA Hubble Telescope

    From NASA/ESA Hubble Telescope

    Mathias Jäger
    ESA/Hubble, Public Information Officer
    Garching bei München, Germany
    Tel: +49 176 62397500
    Email: mjaeger@partner.eso.org

    1
    This image, taken with the Wide Field Camera 3 (WFC3) and the Advanced Camera for Surveys (ACS), both installed on the NASA/ESA Hubble Space Telescope, shows the peculiar galaxy NGC 3256. The galaxy is about 100 million light-years from Earth and is the result of a past galactic merger, which created its distorted appearance. As such, NGC 3256 provides an ideal target to investigate starbursts that have been triggered by galaxy mergers.

    NASA/ESA Hubble WFC3

    NASA/ESA Hubble ACS

    Though it resembles a peaceful rose swirling in the darkness of the cosmos, NGC 3256 is actually the site of a violent clash. This distorted galaxy is the relic of a collision between two spiral galaxies, estimated to have occurred 500 million years ago. Today it is still reeling in the aftermath of this event.

    Located about 100 million light-years away in the constellation of Vela (The Sails), NGC 3256 is approximately the same size as our Milky Way and belongs to the Hydra-Centaurus Supercluster. It still bears the marks of its tumultuous past in the extended luminous tails that sprawl out around the galaxy, thought to have formed 500 million years ago during the initial encounter between the two galaxies, which today form NGC 3256. These tails are studded with young blue stars, which were born in the frantic but fertile collision of gas and dust.

    When two galaxies merge, individual stars rarely collide because they are separated by such enormous distances, but the gas and dust of the galaxies do interact — with spectacular results. The brightness blooming in the centre of NGC 3256 gives away its status as a powerful starburst galaxy, host to vast amounts of infant stars born into groups and clusters. These stars shine most brightly in the far infrared, making NGC 3256 exceedingly luminous in this wavelength domain. Because of this radiation, it is classified as a Luminous Infrared Galaxy.

    NGC 3256 has been the subject of much study due to its luminosity, its proximity, and its orientation: astronomers observe its face-on orientation, that shows the disc in all its splendour. NGC 3256 provides an ideal target to investigate starbursts that have been triggered by galaxy mergers. It holds particular promise to further our understanding of the properties of young star clusters in tidal tails.

    As well as being lit up by over 1000 bright star clusters, the central region of NGC 3256 is also home to crisscrossing threads of dark dust and a large disc of molecular gas spinning around two distinct nuclei — the relics of the two original galaxies. One nucleus is largely obscured, only unveiled in infrared, radio and X-ray wavelengths.

    These two initial galaxies were gas-rich and had similar masses, as they seem to be exerting roughly equal influence on each other. Their spiral disks are no longer distinct, and in a few hundred million years time, their nuclei will also merge and the two galaxies will likely become united as a large elliptical galaxy.

    NGC 3256 was previously imaged through fewer filters by the NASA/ESA Hubble Space Telescope as part of a large collection of 59 images of merging galaxies, released for Hubble’s 18th anniversary on 24th April 2008.

    See the full article here .

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    The Hubble Space Telescope is a project of international cooperation between NASA and the European Space Agency. NASA’s Goddard Space Flight Center manages the telescope. The Space Telescope Science Institute (STScI), is a free-standing science center, located on the campus of The Johns Hopkins University and operated by the Association of Universities for Research in Astronomy (AURA) for NASA, conducts Hubble science operations.

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  • richardmitnick 1:39 pm on May 28, 2018 Permalink | Reply
    Tags: , , , , Forming In Galaxies Beyond The Milky Way, Hubble Catches New Stars, Hubble Space Telescope’s Legacy ExtraGalactic UV Survey (LEGUS), Individually, NASA ESA Hubble   

    From Ethan Siegel: “Hubble Catches New Stars, Individually, Forming In Galaxies Beyond The Milky Way” 

    Ethan Siegel
    May 28, 2018

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    These six images represent the variety of star-forming regions in nearby galaxies. The galaxies are part of the Hubble Space Telescope’s Legacy ExtraGalactic UV Survey (LEGUS), the sharpest, most comprehensive ultraviolet-light survey of star-forming galaxies in the nearby universe. (NASA, ESA, and the LEGUS team)

    LEGUS Hubble Space Telescope’s Legacy ExtraGalactic UV Survey

    NASA/ESA Hubble Telescope

    The legacy of what humanity’s greatest telescope has to teach us about the Universe continues to grow.

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    The Eagle Nebula, famed for its ongoing star formation, contains a large number of Bok globules, or dark nebulae, which have not yet evaporated and are working to collapse and form new stars before they disappear entirely. Although this is from our own galaxy, Hubble can now take us to the stars newly forming in galaxies up to nearly 50 million light years away. (ESA / Hubble & NASA)

    Pillars of Creation. in the Eagle Nebula, NASA, ESA, and the Hubble Heritage Team (STScI/AURA)

    Eagle Nebula NASA/ESA Hubble Public Domain

    When large-enough clouds of gas or dust collapse, star formation is inevitable.

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    An enormous star-forming region in the dwarf galaxy UGCA 281, as imaged by Hubble in the visible and the ultraviolet, as part of the LEGUS survey. The blue light is starlight from hot, young stars reflected off of the background, neutral gas. (NASA, ESA and the LEGUS team)

    They don’t simply form in isolation, but in large clusters, usually containing thousands of new stars.

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    The Whirlpool Galaxy (Messier 51) appears pink along its spiral arms due to a large amount of star formation that’s occurring. In this particular case, a nearby galaxy gravitationally interacting with the Whirlpool galaxy is triggering this star formation, but all spirals rich in gas exhibit some level of new star birth. The LEGUS data has thoroughly confirmed this. ((NASA, ESA, S. Beckwith (STScI), and The Hubble Heritage Team (STScI / AURA))

    From its perch above Earth, the Hubble Space Telescope can view these newborn, individual stars in galaxies beyond the Milky Way.

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    The spiral galaxy NGC 6744, part of the LEGUS survey, showcases new star formation along the spiral arms, where gas and dust are plentiful, but none in the galactic center, which is overwhelmed with stars and contains little gas. (NASA, ESA, and the LEGUS team)

    There are a massive variety of star-forming regions nearby, and Hubble’s new Legacy ExtraGalactic UV Survey (LEGUS) is now the sharpest, most comprehensive one ever.

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    In some galaxies, stars form merely on the outskirts exclusively, leaving the interior regions with only the older stars that pre-existed.(NASA, ESA, and the LEGUS team)

    By imaging 50 nearby, star-forming spiral and dwarf galaxies, astronomers can see how the galactic environment affects star-formation.

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    The dwarf galaxy UGC 5340 is forming stars irregularly, likely due to a gravitational interaction with a companion galaxy that is not pictured here. Gravitational interactions often trigger new star formation, leading to the collapse of interior gas clouds. (NASA, ESA, and the LEGUS team)

    In dwarf galaxies, the most active star-formation occurs away from each galaxy’s center.

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    The dwarf galaxy UGCA 281, shown here as imaged by Hubble in the visible and ultraviolet, is rapidly forming new stars. An older, background population of redder stars is what these newer, bluer stars are superimposed on top of. (NASA, ESA, and the LEGUS team)

    Instead, star-formation is concentrated in clusters where the neutral gas is densest, theoretically triggered by gravitational interactions.

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    The dark swaths that permeate spiral galaxies are neutral clouds of gas and dust, and block visible and ultraviolet light. However, when gravitational collapse triggers the formation of new stars, these regions will light up in pinks and blues as they either ionize or reflect starlight, respectively. (NASA, ESA, and the LEGUS team)

    In the spirals, by contrast, waves of star-formation occur along dark, dusty features tracing the spiral arms.

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    The outskirts of a spiral galaxy, like NGC 3627 shown here, are most often where the newest, youngest, bluest stars can be found in great abundance. (NASA, ESA, and the LEGUS team)

    As the newborn stars heat the nearby gas, it ionizes, leading to a pink color as the electrons recombine with hydrogen ions.

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    Here in spiral galaxy NGC 3368, the newest stars appear to be forming only in the outermost regions of this spiral galaxy, all along what appears to be a single arm. As we learn more about the link between gas, stars, and environment, mysteries like this galaxy will begin to make sense. (NASA, ESA, and the LEGUS team)

    Understanding how star-formation is connected to its environment represents the final link between the initial gas and the end population of stars.

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    By understanding when-and-how stars form under differing environmental conditions, scientists can reconstruct the link between star formation and the galaxies that will give rise to them. Here, the interior, central region of a galaxy doesn’t form new stars, while the outer, dust-rich regions do. (NASA, ESA, and the LEGUS team)

    See the full article here .


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    “Starts With A Bang! is a blog/video blog about cosmology, physics, astronomy, and anything else I find interesting enough to write about. I am a firm believer that the highest good in life is learning, and the greatest evil is willful ignorance. The goal of everything on this site is to help inform you about our world, how we came to be here, and to understand how it all works. As I write these pages for you, I hope to not only explain to you what we know, think, and believe, but how we know it, and why we draw the conclusions we do. It is my hope that you find this interesting, informative, and accessible,” says Ethan

     
  • richardmitnick 8:33 am on May 24, 2018 Permalink | Reply
    Tags: , , , , E0102-72.3: Astronomers Spot a Distant and Lonely Neutron Star, , , NASA ESA Hubble   

    From NASA Chandra: “E0102-72.3: Astronomers Spot a Distant and Lonely Neutron Star” 

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    NASA/Chandra Telescope


    From NASA Chandra

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    Composite

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    X-ray

    3
    Optical
    Credit X-ray (NASA/CXC/ESO/F.Vogt et al); Optical (ESO/VLT/MUSE & NASA/STScI)

    An isolated neutron star — with a low magnetic field and no stellar companion — has been found for the first time outside of the Milky Way galaxy.

    Astronomers used data from NASA’s Chandra X-ray Observatory, the Very Large Telescope, and other telescopes to make this discovery.

    Neutron stars are the ultra dense cores of massive stars that collapse and undergo a supernova explosion.

    Future observations at X-ray, optical, and radio wavelengths should help astronomers better understand this lonely neutron star.

    Astronomers [F.P.A. Vogt, E.S. Bartlett, I.R. Seitenzahl, M.A. Dopita, P. Ghavamian, A.J. Ruiter, J.P. Terry] have discovered a special kind of neutron star for the first time outside of the Milky Way galaxy, using data from NASA’s Chandra X-ray Observatory and the European Southern Observatory’s Very Large Telescope (VLT) in Chile.

    ESO VLT Platform at Cerro Paranal elevation 2,635 m (8,645 ft)

    Neutron stars are the ultra dense cores of massive stars that collapse and undergo a supernova explosion. This newly identified neutron star is a rare variety that has both a low magnetic field and no stellar companion.

    The neutron star is located within the remains of a supernova — known as 1E 0102.2-7219 (E0102 for short) — in the Small Magellanic Cloud, located 200,000 light years from Earth.

    Small Magellanic Cloud. 10 November 2005. ESA/Hubble and Digitized Sky Survey 2

    This new composite image of E0102 allows astronomers to learn new details about this object that was discovered more than three decades ago. In this image, X-rays from Chandra are blue and purple, and visible light data from VLT’s Multi Unit Spectroscopic Explorer (MUSE) instrument are bright red.

    ESO MUSE on the VLT

    Additional data from the Hubble Space Telescope are dark red and green.

    NASA/ESA Hubble Telescope

    Oxygen-rich supernova remnants like E0102 are important for understanding how massive stars fuse lighter elements into heavier ones before they explode. Seen up to a few thousand years after the original explosion, oxygen-rich remnants contain the debris ejected from the dead star’s interior. This debris (visible as a green filamentary structure in the combined image) is observed today hurtling through space after being expelled at millions of miles per hour.

    Chandra observations of E0102 show that the supernova remnant is dominated by a large ring-shaped structure in X-rays, associated with the blast wave of the supernova. The new MUSE data revealed a smaller ring of gas (in bright red) that is expanding more slowly than the blast wave. At the center of this ring is a blue point-like source of X-rays. Together, the small ring and point source act like a celestial bull’s eye.

    The combined Chandra and MUSE data suggest that this source is an isolated neutron star, created in the supernova explosion about two millennia ago. The X-ray energy signature, or “spectrum,” of this source is very similar to that of the neutron stars located at the center of two other famous oxygen-rich supernova remnants: Cassiopeia A (Cas A) and Puppis A. These two neutron stars also do not have companion stars.

    Cassiopeia A false color image using Hubble and Spitzer telescopes and Chandra X-ray Observatory. Credit NASA JPL-Caltech

    NASA/Spitzer Infrared Telescope

    Puppis A Supernova Remnant astrodonimaging.com

    The lack of evidence for extended radio emission or pulsed X-ray radiation, typically associated with rapidly rotating highly-magnetized neutron stars, indicates that the astronomers have detected the X-radiation from the hot surface of an isolated neutron star with low magnetic fields. About ten such objects have been detected in the Milky Way galaxy, but this is the first one detected outside our galaxy.

    But how did this neutron star end up in its current position, seemingly offset from the center of the circular shell of X-ray emission produced by the blast wave of the supernova? One possibility is that the supernova explosion did occur near the middle of the remnant, but the neutron star was kicked away from the site in an asymmetric explosion, at a high speed of about two million miles per hour. However, in this scenario, it is difficult to explain why the neutron star is, today, so neatly encircled by the recently discovered ring of gas seen at optical wavelengths.

    Another possible explanation is that the neutron star is moving slowly and its current position is roughly where the supernova explosion happened. In this case, the material in the optical ring may have been ejected either during the supernova explosion, or by the doomed progenitor star up to a few thousand years before.

    A challenge for this second scenario is that the explosion site would be located well away from the center of the remnant as determined by the extended X-ray emission. This would imply a special set of circumstances for the surroundings of E0102: for example, a cavity carved by winds from the progenitor star before the supernova explosion, and variations in the density of the interstellar gas and dust surrounding the remnant.

    Future observations of E0102 at X-ray, optical, and radio wavelengths should help astronomers solve this exciting new puzzle posed by the lonely neutron star.

    A paper describing these results was published in the April issue of Nature Astronomy.

    See the full article here .


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    NASA’s Marshall Space Flight Center in Huntsville, Ala., manages the Chandra program for NASA’s Science Mission Directorate in Washington. The Smithsonian Astrophysical Observatory controls Chandra’s science and flight operations from Cambridge, Mass.

     
  • richardmitnick 12:03 pm on May 23, 2018 Permalink | Reply
    Tags: , , , , NASA ESA Hubble,   

    From astrobites: “Blurred Lines: degeneracies in modeling exoplanet atmospheres” 

    Astrobites bloc

    From astrobites

    Title: The theory of transmission spectra revisited: a semi-analytical method for interpreting WFC3 data and an unresolved challenge
    Authors: Kevin Heng, Daniel Kitzmann
    First Author’s Institution: University of Bern, Center for Space and Habitability

    Status: Accepted to MNRAS, open access

    Transmission spectroscopy is the most commonly used method to characterize the atmospheres of transiting exoplanets that have been discovered to date. The method is seemingly straightforward: photons from the host star passing through the limb of its transiting exoplanet are absorbed or transmitted by the planetary atmosphere to a varying extent in different wavelengths, which should appear as a variation in observed radius of the exoplanet with respect to wavelength. This variation in transit radius with wavelength, known as transmission spectrum, can then be interpreted by adopting either a forward or inverse modeling approach. This means that you can either start with a set of assumptions for the atmospheric properties (like chemical abundances, cloud properties etc.) and construct a physical model that can be fit to the data, or try solving the inverse problem (also known as retrieval) and infer the atmospheric properties from the measured transmission spectra itself.

    However, there is a good deal of subtlety behind both approaches of constructing theoretical models for transiting exoplanet atmospheres. Today’s paper traces the assumptions and caveats involved in constructing models for observations taken by the Wide Field Camera 3 (WFC3) on the Hubble Space Telescope.

    NASA/ESA Hubble Telescope

    NASA/ESA Hubble WFC3

    In addition to deriving a validated semi-analytical approach from first principles for calculating the transmission spectra in the context of WFC3 observations, authors of today’s paper uncover a crucial and unresolved degeneracy involved in fitting a model to the transmission spectra.

    See the full article here .


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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 1:07 pm on May 17, 2018 Permalink | Reply
    Tags: , , , , , LEGUS survey, NASA ESA Hubble, spacetelescope.org   

    From NASA/ESA Hubble Telescope: “Astronomers Release Most Complete Ultraviolet-Light Survey of Nearby Galaxies” 

    NASA Hubble Banner

    NASA/ESA Hubble Telescope

    From NASA/ESA Hubble Telescope

    May 17, 2018

    Donna Weaver /
    Space Telescope Science Institute, Baltimore, Maryland
    410-338-4493 / 410-338-4514
    dweaver@stsci.edu / villard@stsci.edu

    Ray Villard
    Space Telescope Science Institute, Baltimore, Maryland
    410-338-4514
    villard@stsci.edu

    Daniela Calzetti
    University of Massachusetts, Amherst, Massachusetts
    413-545-3556
    calzettii@astro.umass.edu

    Elena Sabbi
    Space Telescope Science Institute, Baltimore, Maryland
    410-338-4732 / 410-338-4926
    sabbi@stsci.edu

    Linda Smith
    ESA/Space Telescope Science Institute, Baltimore, Maryland
    410-338-4926
    lsmith@stsci.edu

    Mathias Jäger
    ESA/Hubble, Public Information Officer
    Garching bei München, Germany
    Cell: +49 176 62397500
    Email: mjaeger@partner.eso.org

    1
    Hubble samples 50 star-forming spiral and dwarf galaxies

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    LEGUS Galaxies

    From HubbleSite [NASA]

    Much of the light in the universe comes from stars, and yet, star formation is still a vexing question in astronomy.

    To piece together a more complete picture of star birth, astronomers have used the Hubble Space Telescope to look at star formation among galaxies in our own cosmic back yard. The survey of 50 galaxies in the local universe, called the Legacy ExtraGalactic UV Survey (LEGUS), is the sharpest, most comprehensive ultraviolet-light look at nearby star-forming galaxies.

    The LEGUS survey combines new Hubble observations with archival Hubble images for star-forming spiral and dwarf galaxies, offering a valuable resource for understanding the complexities of star formation and galaxy evolution. Astronomers are releasing the star catalogs for each of the LEGUS galaxies and cluster catalogs for 30 of the galaxies, as well as images of the galaxies themselves. The catalogs provide detailed information on young, massive stars and star clusters, and how their environment affects their development.

    The local universe, stretching across the gulf of space between us and the great Virgo cluster of galaxies, is ideal for study because astronomers can amass a big enough sample of galaxies, and yet, the galaxies are close enough to Earth that Hubble can resolve individual stars. The survey will also help astronomers understand galaxies in the distant universe, where rapid star formation took place.

    __________________________________________________________

    Capitalizing on the unparalleled sharpness and spectral range of NASA’s Hubble Space Telescope, an international team of astronomers is releasing the most comprehensive, high-resolution ultraviolet-light survey of nearby star-forming galaxies.

    The researchers combined new Hubble observations with archival Hubble images for 50 star-forming spiral and dwarf galaxies in the local universe, offering a large and extensive resource for understanding the complexities of star formation and galaxy evolution. The project, called the Legacy ExtraGalactic UV Survey (LEGUS), has amassed star catalogs for each of the LEGUS galaxies and cluster catalogs for 30 of the galaxies, as well as images of the galaxies themselves. The data provide detailed information on young, massive stars and star clusters, and how their environment affects their development.

    “There has never before been a star cluster and a stellar catalog that included observations in ultraviolet light,” explained survey leader Daniela Calzetti of the University of Massachusetts, Amherst. “Ultraviolet light is a major tracer of the youngest and hottest star populations, which astronomers need to derive the ages of stars and get a complete stellar history. The synergy of the two catalogs combined offers an unprecedented potential for understanding star formation.”

    How stars form is still a vexing question in astronomy. “Much of the light we get from the universe comes from stars, and yet we still don’t understand many aspects of how stars form,” said team member Elena Sabbi of the Space Telescope Science Institute in Baltimore, Maryland. “This is even key to our existence — we know life wouldn’t be here if we didn’t have a star around.”

    The research team carefully selected the LEGUS targets from among 500 galaxies, compiled in ground-based surveys, located between 11 million and 58 million light-years from Earth. Team members chose the galaxies based on their mass, star-formation rate, and abundances of elements that are heavier than hydrogen and helium. The catalog of ultraviolet objects collected by NASA’s Galaxy Evolution Explorer (GALEX) spacecraft also helped lay the path for the Hubble study.

    The team used Hubble’s Wide Field Camera 3 and the Advanced Camera for Surveys over a one-year period to snap visible- and ultraviolet-light images of the galaxies and their most massive young stars and star clusters.

    NASA/ESA Hubble WFC3

    NASA/ESA Hubble ACS

    The researchers also added archival visible-light images to provide a complete picture.

    The star cluster catalogs contain about 8,000 young clusters whose ages range from 1 million to roughly 500 million years old. These stellar groupings are as much as 10 times more massive than the largest clusters seen in our Milky Way galaxy.

    The star catalogs comprise about 39 million stars that are at least five times more massive than our Sun. Stars in the visible-light images are between 1 million and several billion years old; the youngest stars, those between 1 million and 100 million years old, shine prominently in ultraviolet light.

    The Hubble data provide all of the information to analyze these galaxies, the researchers explained. “We also are offering computer models to help astronomers interpret the data in the star and cluster catalogs,” Sabbi said. “Researchers, for example, can investigate how star formation occurred in one specific galaxy or a set of galaxies. They can correlate the properties of the galaxies with their star formation. They can derive the star-formation history of the galaxies. The ultraviolet-light images may also help astronomers identify the progenitor stars of supernovas found in the data.”

    One of the key questions the survey may help astronomers answer is the connection between star formation and the major structures, such as spiral arms, that make up a galaxy.

    “When we look at a spiral galaxy, we usually don’t just see a random distribution of stars,” Calzetti said. “It’s a very orderly structure, whether it’s spiral arms or rings, and that’s particularly true with the youngest stellar populations. On the other hand, there are multiple competing theories to connect the individual stars in individual star clusters to these ordered structures.

    “By seeing galaxies in very fine detail — the star clusters — while also showing the connection to the larger structures, we are trying to identify the physical parameters underlying this ordering of stellar populations within galaxies. Getting the final link between gas and star formation is key for understanding galaxy evolution.”

    Team member Linda Smith of the European Space Agency (ESA) and the Space Telescope Science Institute, added: “We’re looking at the effects of the environment, particularly with star clusters, and how their survival is linked to the environment around them.”

    The LEGUS survey will also help astronomers interpret views of galaxies in the distant universe, where the ultraviolet glow from young stars is stretched to infrared wavelengths due to the expansion of space. “The data in the star and cluster catalogs of these nearby galaxies will help pave the way for what we see with NASA’s upcoming infrared observatory, the James Webb Space Telescope, developed in partnership with ESA and the Canadian Space Agency (CSA),” Sabbi said.

    Webb observations would be complementary to the LEGUS views. The space observatory will penetrate dusty stellar cocoons to reveal the infrared glow of infant stars, which cannot be seen in visible- and ultraviolet-light images. “Webb will be able to see how star formation propagates over a galaxy,” Sabbi continued. “If you have information on the gas properties, you can really connect the points and see where, when, and how star formation happens.”

    The Hubble Space Telescope is a project of international cooperation between NASA and ESA (European Space Agency). NASA’s Goddard Space Flight Center in Greenbelt, Maryland, manages the telescope. The Space Telescope Science Institute (STScI) in Baltimore, Maryland, conducts Hubble science operations. STScI is operated for NASA by the Association of Universities for Research in Astronomy in Washington, D.C.

    Credits
    NASA, ESA, and D. Calzetti (University of Massachusetts) and the LEGUS team

    Related Links

    LEGUS Team Members
    NASA’s Hubble Portal
    LEGUS Project Portal

    From ESA/Hubble’s Release

    From spacetelescope.org [ESA]

    3
    Using the unparalleled sharpness and ultraviolet observational capabilities of the NASA/ESA Hubble Space Telescope, an international team of astronomers has created the most comprehensive high-resolution ultraviolet-light survey of star-forming galaxies in the local Universe. The catalogue contains about 8000 clusters and 39 million hot blue stars.

    Ultraviolet light is a major tracer of the youngest and hottest stars. These stars are short-lived and intensely bright. Astronomers have now finished a survey called LEGUS (Legacy ExtraGalactic UV Survey) that captured the details of 50 local galaxies within 60 million light-years of Earth in both visible and ultraviolet light.

    The LEGUS team carefully selected its targets from among 500 candidate galaxies compiled from ground-based surveys. They chose the galaxies based on their mass, star-formation rate, and their abundances of elements heavier than hydrogen and helium. Because of the proximity of the selected galaxies, Hubble was able to resolve them into their main components: stars and star clusters. With the LEGUS data, the team created a catalogue with about 8000 young clusters and it also created a star catalogue comprising about 39 million stars that are at least five times more massive than our Sun.

    The data, gathered with Hubble’s Wide Field Camera 3 and Advanced Camera for Surveys, provide detailed information on young, massive stars and star clusters, and how their environment affects their development. As such, the catalogue offers an extensive resource for understanding the complexities of star formation and galaxy evolution.

    One of the key questions the survey may help astronomers answer is the connection between star formation and the major structures, such as spiral arms, that make up a galaxy. These structured distributions are particularly visible in the youngest stellar populations.

    By resolving the fine details of the studied galaxies, while also studying the connection to larger galactic structures, the team aims to identify the physical mechanisms behind the observed distribution of stellar populations within galaxies.

    Figuring out the final link between gas and star formation is key to fully understanding galaxy evolution. Astronomers are studying this link by looking at the effects of the environment on star clusters, and how their survival is linked to their surroundings.

    LEGUS will not only allow astronomers to understand the local Universe. It will also help interpret views of distant galaxies, where the ultraviolet light from young stars is stretched to infrared wavelengths due to the expansion of space. The NASA/ESA/CSA James Webb Space Telescope and its ability to observe in the far infrared will complement the LEGUS views.

    See the full Hubblesite article here .
    See the full ESA/Hubble spacetelescope.org article here .

    Please help promote STEM in your local schools.

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    The Hubble Space Telescope is a project of international cooperation between NASA and the European Space Agency. NASA’s Goddard Space Flight Center manages the telescope. The Space Telescope Science Institute (STScI), is a free-standing science center, located on the campus of The Johns Hopkins University and operated by the Association of Universities for Research in Astronomy (AURA) for NASA, conducts Hubble science operations.

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  • richardmitnick 3:57 pm on May 9, 2018 Permalink | Reply
    Tags: , , , , , NASA ESA Hubble, The remarkable Red Rectangle: A stairway to heaven?"   

    From Hubble via Manu: “The remarkable Red Rectangle: A stairway to heaven?” 11 May 2004 


    Manu Garcia, a friend from IAC.

    The universe around us.
    Astronomy, everything you wanted to know about our local universe and never dared to ask.

    11 May 2004

    Hans Van Winckel
    Catholic University of Leuven, Heverlee, Belgium
    Tel: +32-16-32-70-32
    E-mail: Hans.VanWinckel@ster.kuleuven.ac.be

    Vincent Icke
    Leiden University, Leiden, The Netherlands
    Phone: +31-71-527-58-43
    Cellular: +31-6-5149-5011
    E-mail: icke@strw.LeidenUniv.nl

    Lars Lindberg Christensen
    Hubble European Space Agency Information Centre, Garching, Germany
    Tel: +49-(0)89-3200-6306
    Cellular (24 hr): +49-(0)173-3872-621
    E-mail: lars@eso.org

    Martin Cohen
    University of California, Berkeley, USA
    Tel: +1-510-642-2833
    E-mail: mcohen@astro.berkeley.edu

    Howard Bond
    Space Telescope Science Institute, Baltimore, USA
    Tel: +1-410-338-4718
    E-mail: bond@stsci.edu

    Ted Gull
    NASA Goddard Space Flight Center, Greenbelt, USA
    Tel: +1-301-286-6184
    E-mail: gull@sea.gsfc.nasa.gov

    Donna Weaver
    Space Telescope Science Institute, Baltimore, USA
    Tel: +1-410-338-4493
    E-mail: dweaver@stsci.edu
    NASA Hubble Banner

    NASA/ESA Hubble Telescope

    NASA/ESA Hubble Telescope

    2

    Astronomers may not have observed the fabled “Stairway to Heaven”, but they have photographed something almost as intriguing: ladder-like structures surrounding a dying star.

    This image, taken with the NASA/ESA Hubble Space Telescope, reveals startling new details of one of the most unusual nebulae known in our Galaxy. Catalogued as HD 44179, this nebula is more commonly called the “Red Rectangle” because of its unique shape and colour as seen with ground-based telescopes.

    Hubble has revealed a wealth of new features in the Red Rectangle that cannot be seen by ground-based telescopes looking through the Earth’s turbulent atmosphere. Details of the Hubble study were published in the April 2004 issue of The Astronomical Journal.

    Hans Van Winckel, Catholic University of Leuven, Belgium, the principal investigator for the Hubble observations, says: “The structure of the Red Rectangle revealed by Hubble is surprisingly complex. The features that impress me most look like the rungs of a ladder, although they are actually projections of gas cones, like a series of nested wine glasses filled to their brim with gas and seen from the side.”

    Hubble’s sharp pictures show that the Red Rectangle is not really rectangular, but has an X-shaped structure, that astronomers interpret as arising from outflows of gas and dust from the star in the centre. The cone-like outflows are ejected from the star in two opposing directions. In addition there are straight linking features that look like the rungs on a ladder, making the Red Rectangle look similar to a spider’s web, a shape unlike that of any other known nebula in the sky. These rungs may have arisen in episodes of mass ejection from the star that occur every few hundred years and could represent a series of ‘smoke rings’, seen almost exactly edge-on from our vantage point.

    The star at the centre of the Red Rectangle began its life as a star similar to our Sun. It is now nearing the end of its lifetime, and is in the process of ejecting its outer layers to produce the visible nebula. The shedding of the outer layers began about 14 000 years ago, and in a few thousand years, the star will have become smaller and hotter, releasing a flood of ultraviolet light into the surrounding nebula. When this occurs the gas in the nebula will begin to fluoresce, producing a “planetary nebula”.

    At the present time, however, the star is still so cool that atoms in the nebula do not glow and the surrounding dust particles are only visible as they reflect light from the central star. Exactly which molecules in the dust cloud are responsible for the striking red colour of the Rectangle is not yet clear, but it is likely that they are some kind of hydrocarbon formed in the cool outflows from the central star.

    Another remarkable feature of the Red Rectangle, visible only with the superb resolution of the Hubble telescope, is the dark band passing across the central star. This is the shadow of a dense disc of dust that surrounds the star and obscures it from direct view. The light we see streams out along the axis of the disc, and is scattered towards us by dust particles. Astronomers have found that the central star is actually a close pair of stars orbiting each other with a period of about 10 1/2 months. Interactions between these stars have probably caused the ejection of the thick dust disc that obscures our view of the binary. The disc then funnels subsequent dust and gas outflows out along its axis, forming the bizarre bi-conical structure we see as the rung of the Red Rectangle. The reasons for these fresh periodic ejections of more gas and dust remain unknown.

    The Red Rectangle was first discovered during a rocket flight in the early 1970s, in which astronomers were searching for strong sources of infrared radiation. This infrared source lies about 2 300 light-years from Earth in the direction of the constellation Monoceros. Stars surrounded by clouds of dust are often strong infrared sources because the dust is heated by the starlight and then re-radiates long-wavelength red light. Studies of HD 44179 with ground-based telescopes revealed a rectangular shape in the dust surrounding the star at the centre, leading to the name “Red Rectangle”, coined in 1973 by astronomers Martin Cohen and Mike Merrill.

    This image was made from observations taken on 17 March 1999 with Hubble’s Wide Field Planetary Camera 2.

    NASA/Hubble WFPC2. No longer in service.

    Notes

    Animations and general Hubble Space Telescope background footage are available from: http://www.spacetelescope.org/videos/?search=heic0408

    Interactive, zoomable images are available at: http://www.spacetelescope.org/images/heic0408a/zoomable/

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    The Hubble Space Telescope is a project of international cooperation between NASA and the European Space Agency. NASA’s Goddard Space Flight Center manages the telescope. The Space Telescope Science Institute (STScI), is a free-standing science center, located on the campus of The Johns Hopkins University and operated by the Association of Universities for Research in Astronomy (AURA) for NASA, conducts Hubble science operations.

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  • richardmitnick 12:34 pm on May 9, 2018 Permalink | Reply
    Tags: , , , , , , NASA ESA Hubble,   

    From NASA Chandra: “Messier 82: Images From Space Telescopes Produce Stunning View of Starburst Galaxy” 2006 

    NASA Chandra Banner

    NASA/Chandra Telescope


    From NASA Chandra

    Release Date April 24, 2006 [In social media 5.8.18

    Messier 82:
    Images From Space Telescopes Produce Stunning View of Starburst Galaxy

    1
    Credit X-ray: NASA/CXC/JHU/D.Strickland; Optical: NASA/ESA/STScI/AURA/The Hubble Heritage Team; IR: NASA/JPL-Caltech/Univ. of AZ/C. Engelbracht

    NASA/ESA Hubble Telescope

    Images from three of NASA’s Great Observatories were combined to create this spectacular, multiwavelength view of the starburst galaxy Messier 82 [Cigar Galaxy]. Optical light from stars (yellow-green/Hubble Space Telescope) shows the disk of a modest-sized, apparently normal galaxy.

    Another Hubble observation designed to image 10,000 degree Celsius hydrogen gas (orange) reveals a startlingly different picture of matter blasting out of the galaxy. The Spitzer Space Telescope infrared image (red) shows that cool gas and dust are also being ejected.

    NASA/Spitzer Infrared Telescope

    Chandra’s X-ray image (blue) reveals gas that has been heated to millions of degrees by the violent outflow. The eruption can be traced back to the central regions of the galaxy where stars are forming at a furious rate, some 10 times faster than in the Milky Way Galaxy.

    Many of these newly formed stars are very massive and race through their evolution to explode as supernovas. Vigorous mass loss from these stars before they explode, and the heat generated by the supernovas drive the gas out of the galaxy at millions of miles per hour. It is thought that the expulsion of matter from a galaxy during bursts of star formation is one of the main ways of spreading elements like carbon and oxygen throughout the universe.

    The burst of star formation in Messier 82 is thought to have been initiated by shock waves generated in a close encounter with a large nearby galaxy, Messier 81, about 100 million years ago. These shock waves triggered the collapse of giant clouds of dust and gas in M82. In another 100 million years or so, most of the gas and dust will have been used to form stars, or blown out of the galaxy, so the starburst will subside.

    See the full article here .

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    NASA’s Marshall Space Flight Center in Huntsville, Ala., manages the Chandra program for NASA’s Science Mission Directorate in Washington. The Smithsonian Astrophysical Observatory controls Chandra’s science and flight operations from Cambridge, Mass.

     
  • richardmitnick 2:14 pm on May 2, 2018 Permalink | Reply
    Tags: , , , , Exoplanet WASP-107b, , NASA ESA Hubble   

    From NASA/ESA Hubble Telescope: “Hubble Detects Helium in the Atmosphere of an Exoplanet for the First Time” 

    NASA Hubble Banner

    NASA/ESA Hubble Telescope

    NASA/ESA Hubble Telescope

    May 2, 2018

    Jessica Spake
    University of Exeter, Exeter, United Kingdom
    jspake@astro.ex.ac.uk

    David Sing
    University of Exeter, Exeter, United Kingdom
    011-44-13-9272-5652
    sing@astro.ex.ac.uk

    Mathias Jäger
    ESA/Hubble, Garching, Germany
    011-49-1-76-6239-7500
    mjaeger@partner.eso.org

    Ray Villard
    Space Telescope Science Institute, Baltimore, Maryland
    410-338-4514
    villard@stsci.edu

    1
    Ballooning Atmosphere Extends Tens of Thousands of Miles Above a Gas Giant Planet.

    There may be no shortage of balloon-filled birthday parties or people with silly high-pitched voices on the planet WASP-107b. That’s because NASA’s Hubble Space Telescope was used to detect helium in the atmosphere for the first time ever on a world outside of our solar system. The discovery demonstrates the ability to use infrared spectra to study exoplanet atmospheres.

    Though as far back as 2000 helium was predicted to be one of the most readily-detectable gases on giant exoplanets, until now helium had not been found — despite searches for it. Helium was first discovered on the Sun, and is the second-most common element in the universe after hydrogen. It’s one of the main constituents of the planets Jupiter and Saturn.

    An international team of astronomers led by Jessica Spake of the University of Exeter, UK, used Hubble’s Wide Field Camera 3 to discover helium. The atmosphere of WASP-107b must stretch tens of thousands of miles out into space. This is the first time that such an extended atmosphere has been discovered at infrared wavelengths.

    The Full Story

    Astronomers using NASA’s Hubble Space Telescope have detected helium in the atmosphere of the exoplanet WASP-107b. This is the first time this element has been detected in the atmosphere of a planet outside the solar system. The discovery demonstrates the ability to use infrared spectra to study exoplanet extended atmospheres.

    The international team of astronomers, led by Jessica Spake, a PhD student at the University of Exeter in the UK, used Hubble’s Wide Field Camera 3 to discover helium in the atmosphere of the exoplanet WASP-107b. This is the first detection of its kind.

    NASA/ESA Hubble WFC3

    Spake explained the importance of the discovery: “Helium is the second-most common element in the universe after hydrogen. It is also one of the main constituents of the planets Jupiter and Saturn in our solar system. However, up until now helium had not been detected on exoplanets — despite searches for it.”

    The team made the detection by analyzing the infrared spectrum of the atmosphere of WASP-107b. Previous detections of extended exoplanet atmospheres have been made by studying the spectrum at ultraviolet and optical wavelengths; this detection therefore demonstrates that exoplanet atmospheres can also be studied at longer wavelengths.

    The measurement of an exoplanet’s atmosphere is performed when the planet passes in front of its host star. A tiny portion of the star’s light passes through the exoplanet’s atmosphere, leaving detectable fingerprints in the spectrum of the star. The larger the amount of an element present in the atmosphere, the easier the detection becomes.

    “The strong signal from helium we measured demonstrates a new technique to study upper layers of exoplanet atmospheres in a wider range of planets,” said Spake. “Current methods, which use ultraviolet light, are limited to the closest exoplanets. We know there is helium in the Earth’s upper atmosphere and this new technique may help us to detect atmospheres around Earth-sized exoplanets — which is very difficult with current technology.”

    WASP-107b is one of the lowest density planets known: While the planet is about the same size as Jupiter, it has only 12 percent of Jupiter’s mass. The exoplanet is about 200 light-years from Earth and takes less than six days to orbit its host star.

    The amount of helium detected in the atmosphere of WASP-107b is so large that its upper atmosphere must extend tens of thousands of miles out into space. This also makes it the first time that an extended atmosphere has been discovered at infrared wavelengths.

    Since its atmosphere is so extended, the planet is losing a significant amount of its atmospheric gases into space — between about 0.1 percent to 4 percent of its atmosphere’s total mass every billion years.

    Stellar radiation has a significant effect on the rate at which a planet’s atmosphere escapes. The star WASP-107 is highly active, supporting the atmospheric loss. As the atmosphere absorbs radiation it heats up, so the gas rapidly expands and escapes more quickly into space.

    As far back as the year 2000, it was predicted that helium would be one of the most readily-detectable gases on giant exoplanets, but until now, searches were unsuccessful.

    David Sing, co-author of the study also from the University of Exeter, concluded: “Our new method, along with future telescopes such as NASA’s James Webb Space Telescope, will allow us to analyze atmospheres of exoplanets in far greater detail than ever before.”

    The team’s study appears on May 2, 2018, in the online issue of science journal Nature.

    The international team of astronomers in this study consists of J. Spake (University of Exeter, Exeter, UK), D. Sing (University of Exeter, Exeter, UK; Johns Hopkins University, Baltimore, Maryland), T. Evans (University of Exeter, UK), A. Oklopčić (Harvard-Smithsonian Center for Astrophysics, Cambridge, Massachusetts), V. Bourrier (University Geneva Observatory, Sauverny, Switzerland), L. Kreidberg (Harvard Society of Fellows and Harvard-Smithsonian Center for Astrophysics, Cambridge, Massachusetts), B. Rackham (University of Arizona, Tucson, Arizona), J. Irwin (Harvard-Smithsonian Center for Astrophysics, Cambridge, Massachusetts), D. Ehrenreich and A. Wyttenbach (University of Geneva Observatory, Sauverny, Switzerland), H. Wakeford (Space Telescope Science Institute, Baltimore, Maryland), Y. Zhou (University of Arizona, Tucson, Arizona), K. Chubb (University College London, London, UK), N. Nikolov and J. Goyal (University of Exeter, Exeter, UK), G. Henry and M. Williamson (Tennessee State University, Nashville, Tennessee), S. Blumenthal (Space Telescope Science Institute, Baltimore, Maryland), D. Anderson and C. Hellier (Keele University, Staffordshire, UK), D. Charbonneau (Harvard-Smithsonian Center for Astrophysics, Cambridge, Massachusetts), S. Udry (University of Geneva Observatory, Sauverny, Switzerland), and N. Madhusudhan (University of Cambridge, Cambridge, UK).

    See the full article here .

    Please help promote STEM in your local schools.

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    The Hubble Space Telescope is a project of international cooperation between NASA and the European Space Agency. NASA’s Goddard Space Flight Center manages the telescope. The Space Telescope Science Institute (STScI), is a free-standing science center, located on the campus of The Johns Hopkins University and operated by the Association of Universities for Research in Astronomy (AURA) for NASA, conducts Hubble science operations.

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  • richardmitnick 12:42 pm on April 26, 2018 Permalink | Reply
    Tags: , , , , , , NASA ESA Hubble, Stellar Thief is the Surviving Companion to a Supernova   

    From NASA/ESA Hubble Telescope: “Stellar Thief is the Surviving Companion to a Supernova” 

    NASA Hubble Banner

    NASA/ESA Hubble Telescope

    NASA/ESA Hubble Telescope

    Apr 26, 2018

    Ann Jenkins
    Space Telescope Science Institute, Baltimore, Maryland
    410-338-4488
    jenkins@stsci.edu

    Ray Villard
    Space Telescope Science Institute, Baltimore, Maryland
    410-338-4514
    villard@stsci.edu

    Ori Fox
    Space Telescope Science Institute, Baltimore, Maryland
    410-338-6768
    ofox@stsci.edu

    Stuart Ryder
    Australian Astronomical Observatory, Sydney, Australia
    011-61-2-93724843
    011-61-419-970834 (cell)
    sdr@aao.gov.au

    Alex Filippenko
    University of California, Berkeley, California
    afilippenko@berkeley.edu

    1
    Companion to a Supernova is No Innocent Bystander

    In the fading afterglow of a supernova explosion, astronomers using NASA’s Hubble Space Telescope have photographed the first image of a surviving companion to a supernova. This is the most compelling evidence that some supernovas originate in double-star systems. The companion to supernova 2001ig’s progenitor star was no innocent bystander to the explosion—it siphoned off almost all of the hydrogen from the doomed star’s stellar envelope. SN 2001ig is categorized as a Type IIb stripped-envelope supernova, which is a relatively rare type of supernova in which most, but not all, of the hydrogen is gone prior to the explosion. Perhaps as many as half of all stripped-envelope supernovas have companions—the other half lose their outer envelopes via stellar winds.

    3

    Seventeen years ago, astronomers witnessed a supernova go off 40 million light-years away in the galaxy called NGC 7424, located in the southern constellation Grus, the Crane. Now, in the fading afterglow of that explosion, NASA’s Hubble has captured the first image of a surviving companion to a supernova. This picture is the most compelling evidence that some supernovas originate in double-star systems.

    “We know that the majority of massive stars are in binary pairs,” said Stuart Ryder from the Australian Astronomical Observatory (AAO) in Sydney, Australia and lead author of the study. “Many of these binary pairs will interact and transfer gas from one star to the other when their orbits bring them close together.”

    The companion to the supernova’s progenitor star was no innocent bystander to the explosion. It siphoned off almost all of the hydrogen from the doomed star’s stellar envelope, the region that transports energy from the star’s core to its atmosphere. Millions of years before the primary star went supernova, the companion’s thievery created an instability in the primary star, causing it to episodically blow off a cocoon and shells of hydrogen gas before the catastrophe.

    The supernova, called SN 2001ig, is categorized as a Type IIb stripped-envelope supernova. This type of supernova is unusual because most, but not all, of the hydrogen is gone prior to the explosion. This type of exploding star was first identified in 1987 by team member Alex Filippenko of the University of California, Berkeley.

    How stripped-envelope supernovas lose that outer envelope is not entirely clear. They were originally thought to come from single stars with very fast winds that pushed off the outer envelopes. The problem was that when astronomers started looking for the primary stars from which supernovas were spawned, they couldn’t find them for many stripped-envelope supernovas.

    “That was especially bizarre, because astronomers expected that they would be the most massive and the brightest progenitor stars,” explained team member Ori Fox of the Space Telescope Science Institute in Baltimore. “Also, the sheer number of stripped-envelope supernovas is greater than predicted.” That fact led scientists to theorize that many of the primary stars were in lower-mass binary systems, and they set out to prove it.

    Looking for a binary companion after a supernova explosion is no easy task. First, it has to be at a relatively close distance to Earth for Hubble to see such a faint star. SN 2001ig and its companion are about at that limit. Within that distance range, not many supernovas go off. Even more importantly, astronomers have to know the exact position through very precise measurements.

    In 2002, shortly after SN 2001ig exploded, scientists pinpointed the precise location of the supernova with the European Southern Observatory’s Very Large Telescope (VLT) in Cerro Paranal, Chile. In 2004, they then followed up with the Gemini South Observatory in Cerro Pachón, Chile. This observation first hinted at the presence of a surviving binary companion.

    ESO VLT Platform at Cerro Paranal elevation 2,635 m (8,645 ft)

    Glistening against the awesome backdrop of the night sky above ESO_s Paranal Observatory, four laser beams project out into the darkness from Unit Telescope 4 UT4 of the VLT.


    Gemini South telescope, Cerro Tololo Inter-American Observatory (CTIO) campus near La Serena, Chile, at an altitude of 7200 feet

    Knowing the exact coordinates, Ryder and his team were able to focus Hubble on that location 12 years later, as the supernova’s glow faded. With Hubble’s exquisite resolution and ultraviolet capability, they were able to find and photograph the surviving companion—something only Hubble could do.

    Prior to the supernova explosion, the orbit of the two stars around each other took about a year.

    When the primary star exploded, it had far less impact on the surviving companion than might be thought. Imagine an avocado pit—representing the dense core of the companion star—embedded in a gelatin dessert—representing the star’s gaseous envelope. As a shock wave passes through, the gelatin might temporarily stretch and wobble, but the avocado pit would remain intact.

    In 2014, Fox and his team used Hubble to detect the companion of another Type IIb supernova, SN 1993J. However, they captured a spectrum, not an image. The case of SN 2001ig is the first time a surviving companion has been photographed. “We were finally able to catch the stellar thief, confirming our suspicions that one had to be there,” said Filippenko.

    Perhaps as many as half of all stripped-envelope supernovas have companions—the other half lose their outer envelopes via stellar winds. Ryder and his team have the ultimate goal of precisely determining how many supernovas with stripped envelopes have companions.

    Their next endeavor is to look at completely stripped-envelope supernovas, as opposed to SN 2001ig and SN 1993J, which were only about 90 percent stripped. These completely stripped-envelope supernovas don’t have much shock interaction with gas in the surrounding stellar environment, since their outer envelopes were lost long before the explosion. Without shock interaction, they fade much faster. This means that the team will only have to wait two or three years to look for surviving companions.

    In the future, they also hope to use the James Webb Space Telescope to continue their search.

    Added by Manu:

    4
    Evolution Envelope-Type IIb supernova Unobscured . This graphic illustrates the scenario for the processes that create a supernova envelope type IIb despoiled, in which most, but not all, of the hydrogen envelope is lost before the explosion of the primary star. The four panels show the interaction between SN 2001ig parent star, which finally exploded, and his surviving partner. 1) Two stars orbit each other and getting closer. 2) The more massive star evolves faster, swelling to become a red giant. In this last phase of life, sheds most of its hydrogen envelope in the gravitational field of his companion. As the companion extracted almost all the hydrogen from the doomed star, creates an instability in the primary star. 3) The primary star explodes in a supernova. 4) As the glow of the supernova fades, the surviving partner becomes visible to the Hubble Space Telescope. The faint supernova remnant in the lower left, continues to evolve, but in this case is too weak to be detected by Hubble.

    How supernovae surround the outer casing stripped lose is not entirely clear. Originally it thought it came from single stars with very high winds pushing the outer envelopes. The problem was that when astronomers began searching the primary star from which the supernovae were generated, they could not find in many supernovae devoid envelope.

    “That was especially strange because astronomers expected to be the biggest and brightest progenitor stars,” said team member Ori Fox Science Institute in Baltimore Space Telescope. “In addition, the large number of supernovae devoid envelope is greater than anticipated.” This led scientists to theorize that many of the primary stars in binary systems were lower mass, and prepared to try it.

    Find a binary companion after a supernova explosion is not an easy task. First, it has to be relatively close to Earth that Hubble distance to see such a faint star. SN 2001ig and his companion are at the limit. Within that range of distance, not many supernovae are triggered. More importantly, astronomers must know the exact position through very precise measurements.


    Manu Garcia, a friend from IAC.

    The universe around us.
    Astronomy, everything you wanted to know about our local universe and never dared to ask.

    The paper on this team’s current work was published on March 28, 2018 in The Astrophysical Journal.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    The Hubble Space Telescope is a project of international cooperation between NASA and the European Space Agency. NASA’s Goddard Space Flight Center manages the telescope. The Space Telescope Science Institute (STScI), is a free-standing science center, located on the campus of The Johns Hopkins University and operated by the Association of Universities for Research in Astronomy (AURA) for NASA, conducts Hubble science operations.

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