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  • richardmitnick 8:34 am on August 13, 2016 Permalink | Reply
    Tags: , , Supernova remnants,   

    From TUM: “Interaction of Earth with supernova remnants lasting for one million years” 

    Techniche Universitat Munchen

    Techniche Universitat Munchen

    10.08.2016
    Contact
    Technical University of Munich
    Prof. Dr. Shawn Bishop
    Tel.: +49 89 289 12437
    shawn.bishop@tum.de

    1
    Starry sky through trees. When massive stars with more than ten solar masses have, at the end of their evolution, consumed all of their nuclear fuel supply, they collapse under their gravity and terminate in so-called core-collapse supernovae. (Photo: kaalimies / fotolia)

    Physicists from the Technical University of Munich (TUM) have succeeded in detecting a time-resolved supernova signal in the Earth’s microfossil record. As the group of Prof. Shawn Bishop could show, the supernova signal was first detectable at a time starting about 2.7 million years ago. According to the researcher’s analyses, our solar system spent one Million years to transit trough the remnants of a supernova.

    When massive stars with more than ten solar masses have, at the end of their evolution, consumed all of their nuclear fuel supply, they collapse under their gravity and terminate in so-called core-collapse supernovae. Thereby they eject huge amounts of matter into their surroundings. If a supernova occurs sufficiently close to our solar system, it should leave traces of supernova debris on Earth, in the form of specific radioisotopes.

    Among the elemental species known to be produced in these stars, the radioisotope Fe-60 stands out: This radioisotope has no natural, terrestrial production mechanisms; thus, a detection of Fe-60 atoms within terrestrial reservoirs is proof for the direct deposition of supernova material within our solar system.

    Increased concentration also found in lunar samples

    An excess of Fe-60 was already observed in around two million year old layers of a ferromanganese (FeMn) crust retrieved from the Pacific Ocean and, most recently, in lunar samples. These Fe-60 signals have been attributed to depositions of supernova ejecta. However, due to the slow growth rate of the FeMn crust, the Fe-60 signal had a poor temporal resolution; while lunar regolith cannot record time information because sedimentation does not occur on the moon.

    Now for the first time, physicists of the group of Shawn Bishop, TUM Professor on Nuclear Astrophysics, succeeded in discovering a time-resolved supernova signal in the Earth’s microfossil record, residing in biogenically produced crystals from two Pacific Ocean sediment drill cores. The onset of the Fe-60 signal occurs at around 2.7 Million years and is centered at around 2.2 Million years. The signal significantly ends around 1.7 Million years.

    “Obviously, the solar system spent on Million years to transit through the debris of a supernova,” says Shawn Bishop, who is also a principal investigator at the Excellence Cluster Universe.

    Samples with excellent stratigraphic resolution

    To analyse the entire temporal structure of the Fe-60 signal in terrestrial samples, a geological reservoir with an excellent stratigraphic resolution and high Fe-60 sequestration and low Fe mobility is required, which preserves the Fe-60 fluxes nearly so as they were at the time of deposition, apart from Fe-60 radioactive decay.

    These conditions are fulfilled in the marine sediments from the Pacific Ocean used in this study. At the time of the Fe-60 deposition, iron-sequestering bacteria that live in the ocean sediments incorporated the Fe-60 within their intracellularly-grown chains of magnetite nanocrystals (Fe3O4). After cell death they have fossilized into microfossils. These sediments have grown with a constant sedimentation rate, preserving the intrinsic temporal shape of the supernova signal. “Nevertheless, the Fe-60 concentration in these fossils is so low that it is detectable only by means of ultrasensitive accelerator mass spectroscopy (AMS)”, says Dr. Peter Ludwig, researcher in the group of Shawn Bishop. At the tandem accelerator at the Maier-Leibnitz Laboratory in Garching the physicists could refine the sensitivity of the method so that this discovery was possible the first time ever.

    Supernova event at a distance of at least 300 light years

    The most plausible progenitor star that gave rise to this supernova likely originated in the Scorpius-Centaurus OB association, as analyses of its relative motion have shown. Around 2.3 million years ago it was located at a minimum distance of about 300 light years to the solar system. Over the course of the last 10 to 15 million years, a succession of 15 to 20 supernovae has occurred in this star association. This series of massive stellar explosions has produced a largely matter-free cavity in the interstellar medium of a galactic arm of the Milky Way. Astronomers call this cavity, in which our solar system is located, the Local Bubble.

    Acknowledgement

    In addition to the TUM’s physicists there were also involved: Researchers from the Central Institute for Meteorology and Geodynamics, Geomagnetism and Gravimetry, Vienna, from the TUM Chemistry Department, Elektronenmikroskopie, as well as from the Helmholtz-Zentrum Dresden-Rossendorf, Helmholtz Institute Freiberg for Resource Technology, Dresden.

    The research was funded by the German Research Foundation (DFG) and the Excellence Cluster Universe

    Original publication

    Ludwig et al.: Time resolved 2-million-year-old supernova activity discovered in Earth’s microfossil record
    Proceedings of the National Academy of Sciences, DOI: 10.1073/pnas.1601040113, August 8, 2016

    See the full article here .

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    Techniche Universitat Munchin Campus

    Technische Universität München (TUM) is one of Europe’s top universities. It is committed to excellence in research and teaching, interdisciplinary education and the active promotion of promising young scientists. The university also forges strong links with companies and scientific institutions across the world. TUM was one of the first universities in Germany to be named a University of Excellence. Moreover, TUM regularly ranks among the best European universities in international rankings.

     
  • richardmitnick 2:34 pm on February 19, 2016 Permalink | Reply
    Tags: , , , Supernova remnants   

    From AAS NOVA: “Finding Distances to Type Ia Supernovae” 

    AASNOVA

    Amercan Astronomical Society

    19 February 2016
    Susanna Kohler

    Supernova remnant Crab nebula
    Crab supernova remnant. NASA/ESA Hubble

    NASA Hubble Telescope
    NASA/ESA Hubble

    Type Ia supernovae are known as standard candles due to their consistency, allowing us to measure distances based on their brightness. But what if these explosions aren’t quite as consistent as we thought? Due scientific diligence requires careful checks, so a recent study investigates whether the metallicity of a supernova’s environment affects the peak luminosity of the explosion.

    Metallicity Dependence?

    Type Ia supernovae are incredibly powerful tools for determining distances in our universe. Because these supernovae are formed by white dwarfs that explode when they reach a uniform accreted mass, the supernova peak luminosity is thought to be very consistent. This consistency allows these supernovae to be used as standard candles to measure distances to their host galaxies.

    But what if that peak luminosity is affected by a factor that we haven’t taken into account? Theorists have proposed that the luminosities of Type Ia supernovae might depend on the metallicity of their environments — with high-metallicity environments suppressing supernova luminosities. If this is true, then we could be systematically mis-measuring cosmological distances using these supernovae.

    Testing Abundances

    A team led by Manuel Moreno-Raya, of the Center for Energy, Environment and Technology (CIEMAT) in Spain, has observed 28 Type Ia supernovae in an effort to test for such a metallicity dependence. These supernovae each have independent distance measurements (e.g., from Cepheids or the Tully-Fisher relation).

    Moreno-Raya and collaborators used spectra from the 4.2-m William Herschel Telescope to estimate oxygen abundances in the region where each of these supernovae exploded.

    ING William Herschel Telescope
    ING William Herschel Telescope Interior
    Isaac Newton 4.2 meter William Herschel Telescope

    They then used these measurements to determine if metallicity of the local region affects the luminosity of the supernova.
    Determining Distances

    The authors find that there are indeed differences in peak supernova luminosity based on metallicity of the local environment. Their observations support a trend in which more metal-rich galaxies host less luminous supernovae, whereas lower-metallicity galaxies host supernovae with greater luminosities — consistent with theoretical predictions.

    This observational confirmation suggests that the metallicity of the progenitor may well play a role in peak supernova luminosity and, as a result, the distances at which we estimate they exploded. This systematic effect can, however, be easily corrected for in the distance-estimate procedure.

    As the number of known supernovae is expected to drastically increase with the start of future large surveys such as the Large Synoptic Survey Telescope (LSST) or the Dark Energy Survey (DES), supernova distance measurements will soon be dominated by systematic errors rather than statistical ones.

    LSST Exterior
    LSST Interior
    LSST Camera
    LSST, the building which will house it, and the camera, built by SLAC

    Dark Energy Icon
    DECam
    CTIO Victor M Blanco 4m Telescope
    Dark Energy Survey, the DECam built at FNAL, and the 4 meter CTIO/Victor M Blanco telescope in Chile which houses DECAM

    Correctly accounting for effects such as this apparent metallicity-dependence of supernovae continues to be important for accurately determining distances using Type Ia supernovae as indicators.

    Citation

    Manuel E. Moreno-Raya et al 2016 ApJ 818 L19. doi:10.3847/2041-8205/818/1/L19

    See the full article here .

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  • richardmitnick 7:24 am on April 18, 2015 Permalink | Reply
    Tags: , , , Supernova remnants,   

    From SOFIA: “NASA’s SOFIA Finds Missing Link Between Supernovae and Planet Formation” 

    NASA SOFIA Banner

    SOFIA (Stratospheric Observatory For Infrared Astronomy)

    March 19, 2015
    Last Updated: April 18, 2015
    Editor: Sarah Ramsey

    Felicia Chou
    Headquarters, Washington
    202-358-5241
    felicia.chou@nasa.gov

    Nicholas Veronico

    SOFIA Science Center, Moffett Field, Calif.
    650-604-4589 / 650-224-8726

    nicholas.a.veronico@nasa.gov / nveronico@sofia.usra.edu

    Kate K. Squires

    Armstrong Flight Research Center, Edwards, Calif. 

    661-276-2020 

    kate.k.squires@nasa.gov

    1

    Using NASA’s Stratospheric Observatory for Infrared Astronomy (SOFIA), an international scientific team discovered that supernovae are capable of producing a substantial amount of the material from which planets like Earth can form.

    These findings are published in the March 19 online issue of Science magazine.

    “Our observations reveal a particular cloud produced by a supernova explosion 10,000 years ago contains enough dust to make 7,000 Earths,” said Ryan Lau of Cornell University in Ithaca, New York.

    The research team, headed by Lau, used SOFIA’s airborne telescope and the Faint Object InfraRed Camera for the SOFIA Telescope, FORCAST, to take detailed infrared images of an interstellar dust cloud known as Supernova Remnant Sagittarius A East, or SNR Sgr A East.

    2
    Supernova remnant dust detected by SOFIA (yellow) survives away from the hottest X-ray gas (purple). The red ellipse outlines the supernova shock wave. The inset shows a magnified image of the dust (orange) and gas emission (cyan).Credits: NASA/CXO/Lau et al

    The team used SOFIA data to estimate the total mass of dust in the cloud from the intensity of its emission. The investigation required measurements at long infrared wavelengths in order to peer through intervening interstellar clouds and detect the radiation emitted by the supernova dust.

    Astronomers already had evidence that a supernova’s outward-moving shock wave can produce significant amounts of dust. Until now, a key question was whether the new soot- and sand-like dust particles would survive the subsequent inward “rebound” shock wave generated when the first, outward-moving shock wave collides with surrounding interstellar gas and dust.

    “The dust survived the later onslaught of shock waves from the supernova explosion, and is now flowing into the interstellar medium where it can become part of the ‘seed material’ for new stars and planets,” Lau explained.

    These results also reveal the possibility that the vast amount of dust observed in distant young galaxies may have been made by supernova explosions of early massive stars, as no other known mechanism could have produced nearly as much dust.

    “This discovery is a special feather in the cap for SOFIA, demonstrating how observations made within our own Milky Way galaxy can bear directly on our understanding of the evolution of galaxies billions of light years away,” said Pamela Marcum, a SOFIA project scientist at Ames Research Center in Moffett Field, California.

    For more information about SOFIA, visit:

    http://www.nasa.gov/sofia

    or

    http://www.dlr.de/en/sofia

    For information about SOFIA’s science mission and scientific instruments, visit:

    http://www.sofia.usra.edu

    or

    http://www.dsi.uni-stuttgart.de/index.en.html

    See the full article here.

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    SOFIA is a joint project of NASA and the German Aerospace Center (DLR). The aircraft is based at and the program is managed from NASA Armstrong Flight Research Center’s facility in Palmdale, California. NASA’s Ames Research Center, manages the SOFIA science and mission operations in cooperation with the Universities Space Research Association (USRA) headquartered in Columbia, Maryland, and the German SOFIA Institute (DSI) at the University of Stuttgart.
    NASA

     
  • richardmitnick 4:26 pm on March 19, 2015 Permalink | Reply
    Tags: , , , Supernova remnants,   

    From SOFIA: “NASA’s SOFIA Finds Missing Link Between Supernovae and Planet Formation” 

    NASA SOFIA Banner

    SOFIA (Stratospheric Observatory For Infrared Astronomy)

    March 19, 2015
    Felicia Chou
    Headquarters, Washington
    202-358-5241
    felicia.chou@nasa.gov

    Nicholas Veronico

    SOFIA Science Center, Moffett Field, Calif.
    650-604-4589 / 650-224-8726

    nicholas.a.veronico@nasa.gov / nveronico@sofia.usra.edu

    Kate K. Squires

    Armstrong Flight Research Center, Edwards, Calif. 

    661-276-2020 

    kate.k.squires@nasa.gov

    1
    SOFIA data reveal warm dust (white) surviving inside a supernova remnant. The SNR Sgr A East cloud is traced in X-rays (blue). Radio emission (red) shows expanding shock waves colliding with surrounding interstellar clouds (green). Image Credit: NASA/CXO/Herschel/VLA/Lau et al

    [These two following telescopes are clearly present in the above credit, important to the mission, but unnamed by the writers]

    ESA Herschel
    ESA/Herschel

    NRAO VLA
    NRAO/VLA

    Using NASA’s Stratospheric Observatory for Infrared Astronomy (SOFIA), an international scientific team discovered that supernovae are capable of producing a substantial amount of the material from which planets like Earth can form.

    These findings are published in the March 19 online issue of Science magazine.

    “Our observations reveal a particular cloud produced by a supernova explosion 10,000 years ago contains enough dust to make 7,000 Earths,” said Ryan Lau of Cornell University in Ithaca, New York.

    The research team, headed by Lau, used SOFIA’s airborne telescope and the Faint Object InfraRed Camera for the SOFIA Telescope, FORCAST, to take detailed infrared images of an interstellar dust cloud known as Supernova Remnant Sagittarius A East, or SNR Sgr A East.

    2
    Supernova remnant dust detected by SOFIA (yellow) survives away from the hottest X-ray gas (purple). The red ellipse outlines the supernova shock wave. The inset shows a magnified image of the dust (orange) and gas emission (cyan). Image Credit: NASA/CXO/Lau et al

    The team used SOFIA data to estimate the total mass of dust in the cloud from the intensity of its emission. The investigation required measurements at long infrared wavelengths in order to peer through intervening interstellar clouds and detect the radiation emitted by the supernova dust.

    Astronomers already had evidence that a supernova’s outward-moving shock wave can produce significant amounts of dust. Until now, a key question was whether the new soot- and sand-like dust particles would survive the subsequent inward “rebound” shock wave generated when the first, outward-moving shock wave collides with surrounding interstellar gas and dust.

    “The dust survived the later onslaught of shock waves from the supernova explosion, and is now flowing into the interstellar medium where it can become part of the ‘seed material’ for new stars and planets,” Lau explained.

    These results also reveal the possibility that the vast amount of dust observed in distant young galaxies may have been made by supernova explosions of early massive stars, as no other known mechanism could have produced nearly as much dust.

    “This discovery is a special feather in the cap for SOFIA, demonstrating how observations made within our own Milky Way galaxy can bear directly on our understanding of the evolution of galaxies billions of light years away,” said Pamela Marcum, a SOFIA project scientist at Ames Research Center in Moffett Field, California.

    SOFIA is a heavily modified Boeing 747 Special Performance jetliner that carries a telescope with an effective diameter of 100 inches (2.5 meters) at altitudes of 39,000 to 45,000 feet (12 to 14 km). SOFIA is a joint project of NASA and the German Aerospace Center. The aircraft observatory is based at NASA’s Armstrong Flight Research Center facility in Palmdale, California. The agency’s Ames Research Center in Moffett Field, California, is home to the SOFIA Science Center, which is managed by NASA in cooperation with the Universities Space Research Association in Columbia, Maryland, and the German SOFIA Institute at the University of Stuttgart.

    For more information about SOFIA, visit:

    http://www.nasa.gov/sofia

    or

    http://www.dlr.de/en/sofia

    For information about SOFIA’s science mission and scientific instruments, visit:

    http://www.sofia.usra.edu

    See the full article here.

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    SOFIA is a joint project of NASA and the German Aerospace Center (DLR). The aircraft is based at and the program is managed from NASA Armstrong Flight Research Center’s facility in Palmdale, California. NASA’s Ames Research Center, manages the SOFIA science and mission operations in cooperation with the Universities Space Research Association (USRA) headquartered in Columbia, Maryland, and the German SOFIA Institute (DSI) at the University of Stuttgart.
    NASA

     
  • richardmitnick 12:17 pm on January 30, 2015 Permalink | Reply
    Tags: , , , Supernova remnants   

    From CfA: “CAT Scan of Nearby Supernova Remnant Reveals Frothy Interior” 

    Smithsonian Astrophysical Observatory
    Smithsonian Astrophysical Observatory

    Thursday, January 29, 2015
    Christine Pulliam
    Public Affairs Specialist
    Harvard-Smithsonian Center for Astrophysics
    617-495-7463
    cpulliam@cfa.harvard.edu

    1

    Cassiopeia A, or Cas A for short, is one of the most well studied supernova remnants in our galaxy.

    2
    A false color image of Cassiopeia A (Cas A) using observations from both the Hubble and Spitzer telescopes as well as the Chandra X-ray Observatory
    Date 2005/06/09

    NASA Hubble Telescope
    Hubble

    NASA Spitzer Telescope
    Spitzer

    NASA Chandra Telescope
    Chandra

    But it still holds major surprises. Harvard-Smithsonian and Dartmouth College astronomers have generated a new 3-D map of its interior using the astronomical equivalent of a CAT scan. They found that the Cas A supernova remnant is composed of a collection of about a half dozen massive cavities – or “bubbles.”

    “Our three-dimensional map is a rare look at the insides of an exploded star,” says Dan Milisavljevic of the Harvard-Smithsonian Center for Astrophysics (CfA). This research is being published in the Jan. 30 issue of the journal Science.

    About 340 years ago a massive star exploded in the constellation Cassiopeia. As the star blew itself apart, extremely hot and radioactive matter rapidly streamed outward from the star’s core, mixing and churning outer debris. The complex physics behind these explosions is difficult to model, even with state-of-the-art simulations run on some of the world’s most powerful supercomputers. However, by carefully studying relatively young supernova remnants like Cas A, astronomers can investigate various key processes that drive these titanic stellar explosions.

    “We’re sort of like bomb squad investigators. We examine the debris to learn what blew up and how it blew up,” explains Milisavljevic. “Our study represents a major step forward in our understanding of how stars actually explode.”

    To make the 3-D map, Milisavljevic and co-author Rob Fesen of Dartmouth College examined Cas A in near-infrared wavelengths of light using the Mayall 4-meter telescope at Kitt Peak National Observatory, southwest of Tucson, AZ.

    NOAO Mayall 4 m telescope exterior
    NOAO Mayall 4 m telescope interior
    NOAO Mayall Telescope

    Spectroscopy allowed them to measure expansion velocities of extremely faint material in Cas A’s interior, which provided the crucial third dimension.

    They found that the large interior cavities appear to be connected to – and nicely explain – the previously observed large rings of debris that make up the bright and easily seen outer shell of Cas A. The two most well-defined cavities are 3 and 6 light-years in diameter, and the entire arrangement has a Swiss cheese-like structure.

    The bubble-like cavities were likely created by plumes of radioactive nickel generated during the stellar explosion. Since this nickel will decay to form iron, Milisavljevic and Fesen predict that Cas A’s interior bubbles should be enriched with as much as a tenth of a solar mass of iron. This enriched interior debris hasn’t been detected in previous observations, however, so next-generation telescopes may be needed to find the “missing” iron and confirm the origin of the bubbles.

    The researchers have posted an interactive version of their 3-D map online at https://www.cfa.harvard.edu/~dmilisav/casa-webapp/.

    See the full article here.

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    About CfA

    The Center for Astrophysics combines the resources and research facilities of the Harvard College Observatory and the Smithsonian Astrophysical Observatory under a single director to pursue studies of those basic physical processes that determine the nature and evolution of the universe. The Smithsonian Astrophysical Observatory (SAO) is a bureau of the Smithsonian Institution, founded in 1890. The Harvard College Observatory (HCO), founded in 1839, is a research institution of the Faculty of Arts and Sciences, Harvard University, and provides facilities and substantial other support for teaching activities of the Department of Astronomy. The long relationship between the two organizations, which began when the SAO moved its headquarters to Cambridge in 1955, was formalized by the establishment of a joint center in 1973. The CfA’s history of accomplishments in astronomy and astrophysics is reflected in a wide range of awards and prizes received by individual CfA scientists.

    Today, some 300 Smithsonian and Harvard scientists cooperate in broad programs of astrophysical research supported by Federal appropriations and University funds as well as contracts and grants from government agencies. These scientific investigations, touching on almost all major topics in astronomy, are organized into the following divisions, scientific departments and service groups.

     
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