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  • richardmitnick 7:51 pm on August 17, 2016 Permalink | Reply
    Tags: , , NASA Chandra,   

    From Chandra: “G11.2-0.3: Supernova Ejected from the Pages of History” 

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    NASA Chandra Telescope

    NASA Chandra

    August 17, 2016

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    Composite

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    Credit X-ray: NASA/CXC/NCSU/K.Borkowski et al; Optical: DSS
    References Borkowski, K. et al, 2016, ApJ, 819, 160; arXiv:1602.03531

    New Chandra data of the supernova remnant G11.2-0.3 raise new questions about the timing of its origin.

    Previously, G11.2-0.3 was associated with an event recorded by Chinese observers in 386 CE.

    Chandra observations show that dense gas clouds lie along the line of sight between Earth and G11.2-0.3.

    This new information means that the supernova explosion would have been too faint to be seen with the naked eye from Earth.

    A new look at the debris from an exploded star in our galaxy has astronomers re-examining when the supernova actually happened. Recent observations of the supernova remnant called G11.2-0.3 with NASA’s Chandra X-ray Observatory have stripped away its connection to an event recorded by the Chinese in 386 CE.

    Historical supernovas and their remnants can be tied to both current astronomical observations as well as historical records of the event. Since it can be difficult to determine from present observations of their remnant exactly when a supernova occurred, historical supernovas provide important information on stellar timelines. Stellar debris can tell us a great deal about the nature of the exploded star, but the interpretation is much more straightforward given a known age.

    New Chandra data on G11.2-0.3 show that dense clouds of gas lie along the line of sight from the supernova remnant to Earth. Infrared observations with the Palomar 5-meter Hale Telescope had previously indicated that parts of the remnant were heavily obscured by dust.

    Caltech Palomar 200 inch Hale Telescope
    Caltech Palomar 200 inch Hale Telescope interior
    Caltech Palomar 200 inch Hale Telescope

    This means that the supernova responsible for this object would simply have appeared too faint to be seen with the naked eye in 386 CE. This leaves the nature of the observed 386 CE event a mystery.

    A new image of G11.2-0.3 is being released in conjunction with this week’s workshop titled “Chandra Science for the Next Decade” being held in Cambridge, Massachusetts. While the workshop will focus on the innovative and exciting science Chandra can do in the next ten years, G11.2-0.3 is an example of how this “Great Observatory” helps us better understand the complex history of the Universe and the objects within it.

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    Historic Supernova Candidates. Credit NASA/CXC/SAO

    Taking advantage of Chandra’s successful operations since its launch into space in 1999, astronomers were able to compare observations of G11.2-0.3 from 2000 to those taken in 2003 and more recently in 2013. This long baseline allowed scientists to measure how fast the remnant is expanding. Using this data to extrapolate backwards, they determined that the star that created G11.2-0.3 exploded between 1,400 and 2,400 years ago as seen from Earth.

    Previous data from other observatories had shown this remnant is the product of a “core-collapse” supernova, one that is created from the collapse and explosion of a massive star. The revised timeframe for the explosion based on the recent Chandra data suggests that G11.2-0.3 is one of the youngest such supernovas in the Milky Way. The youngest, Cassiopeia A, also has an age determined from the expansion of its remnant, and like G11.2-0.3 was not seen at its estimated explosion date of 1680 CE due to dust obscuration. So far, the Crab nebula, the remnant of a supernova seen in 1054 CE, remains the only firmly identified historical remnant of a massive star explosion in our galaxy.

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

    This latest image of G11.2-0.3 shows low-energy X-rays in red, the medium range in green, and the high-energy X-rays detected by Chandra in blue. The X-ray data have been overlaid on an optical field from the Digitized Sky Survey, showing stars in the foreground.

    Although the Chandra image appears to show the remnant has a very circular, symmetrical shape, the details of the data indicate that the gas that the remnant is expanding into is uneven. Because of this, researchers propose that the exploded star had lost almost all of its outer regions, either in an asymmetric wind of gas blowing away from the star, or in an interaction with a companion star. They think the smaller star left behind would then have blown gas outwards at an even faster rate, sweeping up gas that was previously lost in the wind, forming the dense shell. The star would then have exploded, producing the G11.2-0.3 supernova remnant seen today.

    The supernova explosion also produced a pulsar – a rapidly rotating neutron star – and a pulsar wind nebula, shown by the blue X-ray emission in the center of the remnant. The combination of the pulsar’s rapid rotation and strong magnetic field generates an intense electromagnetic field that creates jets of matter and anti-matter moving away from the north and south poles of the pulsar, and an intense wind flowing out along its equator.

    A paper describing this result appeared in the March 9th, 2016 issue of The Astrophysical Journal and is available online. The authors are Kazimierz Borkowski and Stephen Reynolds, both of North Carolina State University, as well as Mallory Roberts from New York University.

    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 5:22 pm on August 10, 2016 Permalink | Reply
    Tags: , , Hanny's Voorwerp, NASA Chandra   

    From Chandra: “IC 2497: A Black Hole Story Told by a Cosmic Blob and Bubble” 

    NASA Chandra Banner
    NASA Chandra Telescope

    NASA Chandra

    August 10, 2016

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    Credit X-ray: NASA/CXC/ETH Zurich/L.Sartori et al, Optical: NASA/STScI
    Release Date August 10, 2016

    Hanny’s Voorwerp, a cloud of gas, is glowing due to radiation from the giant black hole at the center of the galaxy IC 2497.

    Astronomers think the giant black hole in IC 2497 used to power a quasar in the past, but has faded in the last 200,000 years.

    Chandra data suggests that jets powered by the black hole have blown a bubble in surrounding gas.

    By observing both of these objects, astronomers can probe the history of IC 2497’s black hole and its effect on its host galaxy.

    Two cosmic structures show evidence for a remarkable change in behavior of a supermassive black hole in a distant galaxy. Using data from NASA’s Chandra X-ray Observatory and other telescopes, astronomers are piecing together clues from a cosmic “blob” and a gas bubble that could be a new way to probe the past activity of a giant black hole and its effect on its host galaxy.

    The Green Blob, a renowned cosmic structure also called “Hanny’s Voorwerp” (which means “Hanny’s object” in Dutch), is located about 680 million light years from Earth. This object was discovered in 2007 by Hanny van Arkel, at the time a school teacher, as part of the citizen science project called Galaxy Zoo.

    Astronomers think that a blast of ultraviolet and X-radiation produced by a supermassive black hole at the center of the galaxy IC 2497 (only 200,000 light years away) excited the oxygen atoms in a gas cloud, giving the Green Blob its emerald glow. At present the black hole is growing slowly and not producing nearly enough radiation to cause such a glow.

    However, the distance of the Green Blob from IC 2497 is large enough that we may be observing a delayed response, or an echo of past activity, from a rapidly growing black hole. Such a black hole would produce copious amounts of radiation from infalling material, categorizing it as a “quasar.”

    If the black hole was growing at a much higher rate in the past and then slowed down dramatically in the past 200,000 years, the glow of the Green Blob could be consistent with the present low activity of the black hole. In this scenario, the blob would become much dimmer in the distant future, as reduced ultraviolet and X-radiation levels from the faded quasar finally reach the cloud.

    In this new composite image of IC 2497 (top object) and the Green Blob (bottom), X-rays from Chandra are purple and optical data from the Hubble Space Telescope are red, green, and blue.

    NASA/ESA Hubble Telescope
    NASA/ESA Hubble Telescope

    New observations with Chandra show that the black hole is still producing large amounts of energy even though it is no longer generating intense radiation as a quasar. The evidence for this change in the black hole’s activity comes from hot gas in the center of IC 2497 detected in a long exposure by Chandra. The center of the X-ray emission shows cooler gas, which astronomers interpret as a large bubble in the gas.

    Astronomers suspect this bubble may have been created when a pair of jets from the black hole blew away the hot gas. In this scenario, the energy produced by the supermassive black hole has changed from that of a quasar, when energy is radiated in a broad beam, to more concentrated output in the form of collimated jets of particles and consistent with the observed radio emission in this source.

    Such changes in behavior from strong radiation to strong outflow are seen in stellar-mass black holes that weigh about ten times that of the Sun, taking place over only a few weeks. The much higher mass of the black hole in IC 2497 results in much slower changes over many thousands of years.

    The citizen and professional scientists of the Galaxy Zoo project have continued to hunt for objects like the Green Blob. Many smaller versions of the Green Blob have been found (dubbed “Voorwerpjes” or “little objects” in Dutch.) These latest results from Chandra suggest that fading quasars identified as Voorwerpjes are good places to search for examples of supermassive black holes affecting their surroundings.

    A paper on these results recently appeared in Monthly Notices of the Royal Astronomical Society and is available online [http://arxiv.org/abs/1601.07550]. The authors of the paper are Lia Sartori (ETH Zurich), Kevin Schawinski (ETH Zurich), Michael Koss (ETH Zurich), Ezequiel Treister (University of Concepcion, Chile), Peter Maksym (Harvard-Smithsonian Center for Astrophysics), William Keel (University of Alabama, Tuscaloosa), C. Megan Urry (Yale University), Chris Lintott (Oxford University), and O. Ivy Wong (University of Western Australia).

    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 5:08 am on July 28, 2016 Permalink | Reply
    Tags: , , Magnetic Field Of Sun and Its Kin, NASA Chandra,   

    From Chandra: “Astronomers Gain New Insight into Magnetic Field Of Sun and Its Kin” 

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    NASA Chandra Telescope

    NASA Chandra

    July 27, 2016
    Molly Porter
    Marshall Space Flight Center, Huntsville, Ala.
    256-544-0034
    molly.a.porter@nasa.gov

    Megan Watzke
    Chandra X-ray Center, Cambridge, Mass.
    617-496-7998
    mwatzke@cfa.harvard.edu

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    An artist’s illustration depicts the interior of a low-mass star, such as GJ 3253, a low-mass red dwarf star about 31 light years away from Earth, seen in an X-ray image from Chandra in the inset.
    Credits: X-ray: NASA/CXC/Keele Univ./N. Wright et al; Optical: DSS

    Astronomers have used data from NASA’s Chandra X-ray Observatory to make a discovery that may have profound implications for understanding how the magnetic field in the Sun and stars like it are generated.

    Researchers have discovered that four old red dwarf stars with masses less than half that of the Sun are emitting X-rays at a much lower rate than expected.

    A new study of four low-mass stars may have important implications for understanding the magnetic field of the Sun.

    Magnetic fields are responsible for solar storms that can generate auroras, knock out satellites, and affect astronauts in space.

    X-ray emission is an excellent indicator of a star’s magnetic field strength.

    Two low-mass stars observed with Chandra and two by ROSAT showed their X-ray emission was similar to that of stars like the Sun.

    NASA/ROSAT satellite
    DLR/NASA ROSAT satellite

    X-ray emission is an excellent indicator of a star’s magnetic field strength so this discovery suggests that these stars have much weaker magnetic fields than previously thought.

    Since young stars of all masses have very high levels of X-ray emission and magnetic field strength, this suggests that the magnetic fields of these stars weakened over time. While this is a commonly observed property of stars like our Sun, it was not expected to occur for low-mass stars, as their internal structure is very different.

    The Sun and other stars are giant spheres of superheated gas. The Sun’s magnetic field is responsible for producing sunspots, its 11-year cycle, and powerful eruptions of particles from the solar surface. These solar storms can produce spectacular auroras on Earth, damage electrical power systems, knock out communications satellites, and affect astronauts in space.

    “We have known for decades that the magnetic field on the Sun and other stars plays a huge role in how they behave, but many details remain mysterious,” said lead author Nicholas Wright of Keele University in the United Kingdom. “Our result is one step in the quest to fully understand the Sun and other stars.”

    The rotation of a star and the flow of gas in its interior both play a role in producing its magnetic field. The rotation of the Sun and similar stars varies with latitude (the poles versus the equator) as well as in depth below the surface. Another factor in the generation of magnetic field is convection. Similar to the circulation of warm air inside an oven, the process of convection in a star distributes heat from the interior of the star to its surface in a circulating pattern of rising cells of hot gas and descending cooler gas.

    Convection occurs in the outer third (by radius) of the Sun, while the hot gas closer to the core remains relatively still. There is a difference in the speed of rotation between these two regions. Many astronomers think this difference is responsible for generating most of the magnetic field in the Sun by causing magnetic fields along the border between the convection zone and the core to wind up and strengthen. Since stars rotate more slowly as they age, this also plays a role in how the magnetic field of such stars weakens with time

    “In some ways you can think of the inside of a star as an incredibly complicated dance with many, many dancers,” said co-author Jeremy Drake of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass. “Some dancers move with each other while others move independently. This motion generates magnetic field, but how it works in detail is extremely challenging to determine.”

    For stars much less massive than the Sun, convection occurs all the way into the core of the star. This means the boundary between regions with and without convection, thought to be crucial for generating magnetic field in the Sun, does not exist. One school of thought has been that magnetic field is generated mostly by convection in such stars. Since convection does not change as a star ages, their magnetic fields would not weaken much over time.

    By studying four of these low-mass red dwarf stars in X-rays, Wright and Drake were able to test this hypothesis. They used NASA’s Chandra X-ray Observatory to study two of the stars and data from the ROSAT satellite to look at two others.

    “We found that these smaller stars have magnetic fields that decrease as they age, exactly as it does in stars like our Sun,” said Wright. “This really goes against what we would have expected.”

    These results imply that the interaction along the convection zone-core boundary does not dominate the generation of magnetic field in stars like our Sun, since the low mass stars studied by Wright and Drake lack such a region and yet their magnetic properties are very similar.

    A paper describing these results by Wright and Drake appears in the July 28th issue of the journal Nature. NASA’s Marshall Space Flight Center in Huntsville, Alabama, manages the Chandra program for NASA’s Science Mission Directorate in Washington. The Smithsonian Astrophysical Observatory in Cambridge, Massachusetts, controls Chandra’s science and flight operations.

    Read More from NASA’s Chandra X-ray Observatory.

    For more Chandra images, multimedia and related materials, visit:

    http://www.nasa.gov/chandra

    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 5:16 pm on July 14, 2016 Permalink | Reply
    Tags: , , GRB's, NASA Chandra   

    From Chandra: “GRB 140903A: Chandra Finds Evidence for Violent Stellar Merger” 

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    NASA Chandra

    July 14, 2016

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    Credit X-ray: NASA/CXC/Univ. of Maryland/E. Troja et al, Optical: Lowell Observatory’s Discovery Channel Telescope/E.Troja et al.
    Illustration: NASA/CXC/M.Weiss
    Release Date July 14, 2016

    Astronomers have the strongest evidence to date that violent stellar mergers produce pencil-thin jets.

    This means that a majority of these events will not be detected because they will not be pointed where telescopes can detect them.

    This result has implications for estimating the number of such mergers that may detected with gravitational wave observatories.

    Chandra was used to study X-ray emission from the gamma-ray burst, allowing the width of the jet to be estimated.

    Gamma-ray bursts, or GRBs, are some of the most violent and energetic events in the Universe. Although these events are the most luminous explosions in the universe, a new study using NASA’s Chandra X-ray Observatory, NASA’s Swift satellite and other telescopes suggests that scientists may be missing a majority of these powerful cosmic detonations.

    NASA/SWIFT Telescope
    NASA/SWIFT Telescope

    Astronomers think that some GRBs are the product of the collision and merger of two neutron stars or a neutron star and a black hole. The new research gives the best evidence to date that such collisions will generate a very narrow beam, or jet, of gamma rays. If such a narrow jet is not pointed toward Earth, the GRB produced by the collision will not be detected.

    Collisions between two neutron stars or a neutron star and black hole are expected to be strong sources of gravitational waves that could be detected whether or not the jet is pointed towards the Earth. Therefore, this result has important implications for the number of events that will be detectable by the Laser Interferometry Gravitational-Wave Observatory (LIGO) and other gravitational wave observatories.

    MIT Advanced Ligo
    VIRGO Collaboration bloc

    On September 3, 2014, NASA’s Swift observatory picked up a GRB – dubbed GRB 140903A due to the date it was detected. Scientists used optical observations with the Gemini Observatory telescope in Hawaii to determine that GRB 140903A was located in a galaxy about 3.9 billion light years away, relatively nearby for a GRB.

    Gemini/North telescope
    Gemini/North telescope at Mauna Kea, Hawaii, USA

    The large panel in the graphic is an illustration showing the aftermath of a neutron star merger, including the generation of a GRB. In the center is a compact object – either a black hole or a massive neutron star – and in red is a disk of material left over from the merger, containing material falling towards the compact object. Energy from this infalling material drives the GRB jet shown in yellow. In orange is a wind of particles blowing away from the disk and in blue is material ejected from the compact object and expanding at very high speeds of about one tenth the speed of light.

    The image on the left of the two smaller panels shows an optical view from the Discovery Channel Telescope (DCT) with GRB 140903A in the middle of the square and a close-up X-ray view from Chandra on the right.

    Discovery Channel Telescope at Happy Jack AZ
    Discovery Channel Telescope at Happy Jack AZ, USA

    The bright star in the optical image is unrelated to the GRB.

    The gamma-ray blast lasted less than two seconds. This placed it into the “short GRB” category, which astronomers think are the output from neutron star-neutron star or black hole-neutron star collisions eventually forming either a black hole or a neutron star with a strong magnetic field. (The scientific consensus is that GRBs that last longer than two seconds result from the collapse of a massive star.)

    About three weeks after the Swift discovery of GRB 140903A, a team of researchers led by Eleonora Troja of the University of Maryland, College Park (UMD), observed the aftermath of the GRB in X-rays with Chandra. Chandra observations of how the X-ray emission from this GRB decreases over time provide important information about the properties of the jet.

    Specifically, the researchers found that the jet is beamed into an angle of only about five degrees based on the X-ray observations, plus optical observations with the Gemini Observatory and the DCT and radio observations with the National Science Foundation’s Karl G. Jansky Very Large Array.

    NRAO/VLA, on the Plains of San Agustin fifty miles west of Socorro, NM, USA
    NRAO/VLA, on the Plains of San Agustin fifty miles west of Socorro, NM, USA

    This is roughly equivalent to a circle with the diameter of your three middle fingers held at arms length. This means that astronomers are detecting only about 0.4% of this type of GRB when it goes off, since in most cases the jet will not be pointed directly at us.

    Previous studies by other astronomers had suggested that these mergers could produce narrow jets. However, the evidence in those cases was not as strong because the rapid decline in light was not observed at multiple wavelengths, allowing for explanations not involving jets.

    Several pieces of evidence link this event to the merger of two neutron stars, or between a neutron star and black hole. These include the properties of the gamma ray emission, the old age and the low rate of stars forming in the GRB’s host galaxy and the lack of a bright supernova. In some previous cases strong evidence for this connection was not found.

    New studies have suggested that such mergers could be the production site of elements heavier than iron, such as gold. Therefore, the rate of these events is also important to estimate the total amount of heavy elements produced by these mergers and compare it with the amounts observed in the Milky Way galaxy.

    A paper describing these results was recently accepted for publication in The Astrophysical Journal and is available online. The first author of this paper is Eleonora Troja and the co-authors are T. Sakamoto (Aoyama Gakuin University, Japan), S.Cenko (GSFC), A. Lien (University of Maryland, Baltimore), N. Gehrels (GSFC), A. Castro-Tirado (IAA-CSIC, Spain), R. Ricci (INAF-Istituto di Radioastronomia, Italy), J. Capone, V. Toy, & A. Kutyrev (UMD), N. Kawai (Tokyo Institute of Technology, Japan), A. Cucchiara (GSFC), A. Fruchter (STScI), J.Gorosabel (UMD), S. Jeong (IAA-CSIC), A. Levan (University of Warwick, UK), D. Perley (University of Copenhagen, Denmark), R.Sanchez-Ramirez (Instituto de Astrof ́ısica de Andaluc ́ıa, Spain), N.Tanvir (University of Leicester, UK), S. Veilleux (UMD).

    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 7:06 pm on June 27, 2016 Permalink | Reply
    Tags: , , Clandestine Black Hole May Represent New Population, NASA Chandra,   

    From Chandra: “VLA J2130+12: Clandestine Black Hole May Represent New Population” 

    NASA Chandra Banner
    NASA Chandra Telescope

    NASA Chandra

    6.27.16

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    X-ray: NASA/CXC/Univ. of Alberta/B.Tetarenko et al; Optical: NASA/STScI; Radio: NSF/AUI/NRAO/Curtin Univ./J. Miller-Jones
    Release Date June 27, 2016

    The true identity of an unusual source in the Milky Way galaxy has been revealed.

    This object contains a very quiet black hole, a few times the Sun’s mass, about 7,200 light years from Earth.

    This discovery implies that there could be many more black holes in the galaxy than previously accounted for.

    Chandra data show the source can only be giving off a very small amount of X-rays, an important clue to its true nature.

    Astronomers have identified the true nature of an unusual source in the Milky Way galaxy. As described in our latest press release, this discovery implies that there could be a much larger number of black holes in the Galaxy that have previously been unaccounted for.

    The result was made by combining data from many different telescopes that detect various forms of light, each providing key pieces of information. These telescopes included NASA’s Chandra X-ray Observatory, the Hubble Space Telescope, NSF’s Karl G. Jansky Very Large Array (VLA), Green Bank Telescope, Arecibo Observatory, and the European Very Long Baseline Interferometry Network.

    NASA/ESA Hubble Telescope
    NASA/ESA Hubble Telescope

    NRAO/VLA, on the Plains of San Agustin fifty miles west of Socorro, NM, USA
    NRAO/VLA, on the Plains of San Agustin fifty miles west of Socorro, NM, USA

    NRAO/GBT radio telescope, West Virginia
    NRAO/GBT radio telescope, West Virginia, USA

    NAIC/Arecibo Observatory, Puerto Rico, USA
    NAIC/Arecibo Observatory, Puerto Rico, USA

    European VLBI
    European VLBI

    The collaborative nature of this study is depicted in this multi-panel graphic. The large panel shows a composite Chandra and optical image of the globular cluster M15 located in our galaxy, where the X-ray data are purple and the optical data are red, green and blue. The source being studied here is bright in radio waves, as shown in the close-up VLA image, but the Chandra data reveal it can only be giving off a very small amount of X-rays.

    This new study indicates this source, called VLA J213002.08+120904 (VLA J2130+12 for short), contains a black hole a few times the mass of our Sun that is very slowly pulling in material from a companion star. At this paltry feeding rate, VLA J2130+12 was not previously flagged as a black hole since it lacks some of the telltale signs that black holes in binary systems typically display.

    Previously, most astronomers thought that VLA J2130+12 was probably a distant galaxy. Precise measurements from the radio telescopes showed that this source was actually well within our Galaxy and about five times closer to us than M15. Hubble data identified the companion star in VLA J2130+12 having only about one-tenth to one-fifth the mass of the Sun.

    The observed radio brightness and the limit on the X-ray brightness from Chandra allowed the researchers to rule out other possible interpretations, such as an ultra-cool dwarf star, a neutron star, or a white dwarf pulling material away from a companion star.

    Because this study only covered a very small patch of sky, the implication is that there should be many of these quiet black holes around the Milky Way. The estimates are that tens of thousands to millions of these black holes could exist within our Galaxy, about three to thousands of times as many as previous studies have suggested.

    A paper describing these results appeared in the Astrophysical Journal. The authors were Bailey Tetarenko (University of Alberta), Arash Bahramian (Alberta), Robin Aranson (Alberta), James Miller-Jones (International Center for Radio Astronomy Research), Serena Repetto (Technion), Craig Heinke (Alberta), Tom Maccarone (Texas Tech University), Laura Chomiuk (Michigan State Univsersity), Gregory Sivakoff (Alberta), Jay Strader (Michigan State), Franz Kirsten (ICRAR), and Wouter Vlemmings (Chalmers University of Technology).

    See the full article here .

    Please help promote STEM in your local schools.

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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 9:06 am on June 14, 2016 Permalink | Reply
    Tags: "Coding (and Coloring) the Universe, , , NASA Chandra,   

    From Chandra: Women in Science “Coding (and Coloring) the Universe” 

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    NASA Chandra

    2016-06-13
    Kimberly K. Arcand

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    Micro to macro
    Illustration: NASA/CXC/K.Divona

    When people ask me what I do for work, I often say that I’m a storyteller. It’s not that I stand on a stage with a microphone and narrate long tales to a rapt audience.

    My stories are told differently, not through voice or music, but through lines of code and technical applications. They are stories, of science.

    As an undergraduate, I began my career in molecular biology, looking at the tiny organisms that can transmit Lyme disease to humans aboard the Ixodes Scapularis (a.k.a., the Deer tick). But by the time I graduated, I was moving on to learn about another type of science: that of computers.

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    Binary Code
    Credit: Christiaan Colen, CC BY-SA 2.0

    I didn’t quite realize this as a fresh-out-of-college graduate, but coding is mostly about telling stories. Like many good stories you want to begin at the beginning. The main characters need to be carefully crafted, follow a compelling plot, and arrive at some conclusion, whether a happy ending or not. To make this happen, you use vocabulary and the rules of grammar to change and edit how your story is told.

    The difference between more traditional storytelling and that in computer science is that you must use a language foreign to many. Instead of French, German or Arabic, you speak one of the languages of coding, weaving together multiple plot lines: in this case, those of the computer, the code’s functions, and the end user. Your language might be C++, Perl, Java or SQL.

    This is what I’ve done in my career, albeit covering quite different topics than what I started looking at under a microscope. For the past two decades, I have worked for NASA’s Chandra X-ray Observatory. This telescope in space looks at some of the most violent and energetic phenomena in the Universe – from black holes to exploded stars.

    I work as the Visualization Lead for Chandra and am responsible for a talented team of people who take the data – the information -from this multi-billion-dollar observatory and translate it into products that people from any background can access and use.

    In this role, I have attended countless technology and science conferences, speaking engagements and events. Often I would present talks and work with classes of students, and groups for kids.

    As has been noted by many, I was surprised and disappointed to find that there seemed to be fewer technical women in or entering the field of computer science than I had seen even when I was an undergraduate back in the 90’s. Surveys from the Computing Research Association reported that less than 12% of bachelor degrees in computer science were awarded women between 2010-11.

    There are now many excellent programs out there to address the gender gap in coding, such as Girls Who Code, Women Who Code, Girl Develop It, etc., along with many other groups that address STEM (science, technology, engineering and math) as a whole. I felt like I had an obligation to formulate activities that could work separately or with such groups with like-minded colleagues of my own.

    This became possible when my group joined forces with Google and the American Astronomical Society (AAS). A couple years back, a conversation started between two neighbors, David Bau from Google at the time, and Gus Muench from the AAS. They had a few brief discussions about putting together a coding in astronomy tutorial for Computer Science Education Week and the Hour of Code. They wanted to create a coding exercise for kids to learn about RGB (red, green and blue) color on the computer based on the open-source Pencil Code platform.

    Gus reached out to me and asked if I wanted to be involved in bringing their idea to fruition. I was immediately excited about the project and dug right in. We formed a team with two educators from Google CS First and within a few weeks built up the coding exercise and video tutorial “Recoloring the Universe.”

    The activity was one of those missing links I had been looking for. It offered a real-world example, a way to show — and not just tell — about the type of work you can do in computer science (and astronomy). And the content connects so well with similar processes done in other scientific fields from molecular biology to medicine, that it’s primed for expansion.

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    Data, from astronomy to molecular biology. Illustration: NASA/CXC/K.Divona.

    In my experience, astronomy is a very accessible science. In addition to covering exciting topics, astronomy is also highly visual. The images are often so jaw dropping to look at, they can attract all on their own.

    By combining the how-to of coding with the discoveries of astronomy, we’ve developed a program that can tap into the best of both worlds. With this activity, we can enable others to tell a story about something in the Universe. The aim is to help show that computing does not end with computers, but extends much further into real world applications.

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    Computing does not end with computers
    Illustration: NASA/CXC/M.Weiss

    Since we’ve developed the “Recoloring the Universe” Pencil code project, we’ve presented it to many dozens of schools and groups, with perhaps half of the groups with a near majority of girls in the audience. I don’t expect each one of them to become coders or astronomers, but I hope that some of them will see that they can be if they choose to do so.

    This is the type of amazing potential that could be unleashed into the world after the White House’s United State of Women event. Let’s give everyone an opportunity and the confidence to follow their dream and tell their own story, whether it’s a story about science or not­­. (Follow along at #StateofWomen)

    See the full article here .

    Please help promote STEM in your local schools.

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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 11:41 am on June 13, 2016 Permalink | Reply
    Tags: , , NASA Chandra, TW Hya: Smaller Stars Pack Big X-ray Punch For Would-be Planets   

    From Chandra: “TW Hya: Smaller Stars Pack Big X-ray Punch For Would-be Planets” 

    NASA Chandra Banner

    NASA Chandra Telescope

    NASA Chandra

    1
    Illustration
    Credit X-ray: NASA/CXC/RIT/J.Kastner et al; Illustration: NASA/CXC/M.Weiss
    Release Date June 13, 2016
    Scale Inset image is 1.23 arcmin across (about 0.07 light years)
    Constellation Hydra
    Observation Date 01 Apr 2011
    Observation Time 4 hours 10 min.
    References Kastner, J. et al. 2016, AJ, (accepted); arXiv:1603.09307

    Young stars less massive than the Sun can blast planet-forming disks surrounding them with powerful amounts of X-rays.

    Scientists often look for exoplanets around such stars because they have properties more favorable for detection.

    This result reveals clues about the star formation process and the survival rate of planet-forming disks.

    Chandra data was used to look at the intensity of X-rays produced by the stars and infrared data showed whether the system had a planet-forming disk.

    Young stars much less massive than the Sun can unleash a torrent of X-ray radiation that can significantly shorten the lifetime of planet-forming disks surrounding these stars. This result comes from a new study of a group of nearby stars using data from NASA’s Chandra X-ray Observatory and other telescopes.

    Researchers found evidence that intense X-ray radiation produced by some of the young stars in the TW Hya association (TWA), which on average is about 160 light years from Earth, has destroyed disks of dust and gas surrounding them. These disks are where planets form. The stars are only about 8 million years old, compared to the 4.5-billion-year age of the Sun. Astronomers want to learn more about systems this young because they are at a crucial age for the birth and early development of planets.

    Another key difference between the Sun and the stars in the study involves their mass. The TWA stars in the new study weigh between about one tenth to one half the mass of the Sun and also emit less light. Until now, it was unclear whether X-ray radiation from such small, faint stars could affect their planet-forming disks of material. These latest findings suggest that a faint star’s X-ray output may play a crucial role in determining the survival time of its disk. These results mean that astronomers may have to revisit current ideas on the formation process and early lives of planets around these faint stars.

    Using X-ray data from NASA’s Chandra X-ray Observatory, the European Space Agency’s XMM-Newton observatory and ROSAT (the ROentgenSATellite), the team looked at the intensity of X-rays produced by a group of stars in the TWA, along with how common their star-forming disks are.

    ESA/XMM Newton
    ESA/XMM Newton

    NASA ROSAT staellite
    “ESA/ROSAT satellite

    They split the stars into two groups to make this comparison. The first group of stars had masses ranging from about one third to one half that of the Sun. The second group contained stars with masses only about one tenth that of the Sun, which included relatively massive brown dwarfs, objects that do not have sufficient mass to generate self-sustaining nuclear reactions in their cores.

    The researchers found that, relative to their total energy output, the more massive stars in the first group produce more X-rays than the less massive ones in the second. To find out how common planet-forming disks in the groups were, the team used data from NASA’s Wide-Field Infrared Survey Explorer (WISE) and, in some cases, ground-based spectroscopy previously obtained by other teams.

    NASA/Wise Telescope
    NASA/Wise Telescope

    They found that all of the stars in the more massive group had already lost their planet-forming disks, but only about half of the stars in the less massive group had lost their disks. This suggests that X-rays from the more massive stars are speeding up the disappearance of their disks, by heating disk material and causing it to “evaporate” into deep space.

    A typical star and planet-forming disk from each of these two groups of stars are shown in the illustrations. The illustration above depicts one of the relatively high mass stars, which has a large number of flares and spots. This is a sign of its enhanced X-ray production, which is thinning and destroying the remnants of its planet-forming disk.

    Another illustration (below) shows one of the lower mass, fainter stars. Because it is not as active in X-rays, it has retained a thicker disk that represents a more suitable environment to form planets.

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    The planet formation process would cause gaps, not shown in this illustration, to appear in the disk. The streams near the center show how matter from the disk is still falling onto the star. These illustrations, which are not to scale – the stars are actually miniscule in size when compared with their surrounding disks – are accompanied by a Chandra image of young binary star system that was included in the new study of the TWA.

    In previous studies, astronomers found that 10-million-year-old stars in the Upper Scorpius region, another star-forming group, displayed a similar trend of an increase in the lifetime of disks for lower mass stars. However, the Upper Scorpius work did not incorporate X-ray data that might offer an explanation for this trend, which is one reason why this new study of the 8-million-year-old TWA is important. Another reason is that theoretical models of the evolution of planet-forming disks generally predict that the lifetimes of disks should have very little dependence on the mass of the star. The new results for the “puny” TWA stars point to the need to revisit disk evolution models to account for the range in the X-ray outputs of very low-mass stars.

    In searching for planets outside of our Solar System, many astronomers have focused their efforts on observing stars less massive than the Sun, like those described here. Such stars may offer some of the best targets for direct imaging of exoplanets in the so-called habitable zone, the star-to-planet distance range where liquid water could exist and life may eventually flourish. These low mass stars are also attractive targets because they are relatively faint and planets in their habitable zones should be easier to detect and investigate.

    These results appear in The Astronomical Journal and are available online. The authors of this paper are Joel Kastner (Rochester Institute of Technology), David Principe (Universidad Diego Portales, Chile), Kristina Punzi (RIT), Beate Stelzer(INAF Palermo, Italy), Uma Gorti (SETI Institute), Ilaria Pascucci (University of Arizona), and CostanzaArgiroffi (INAF).

    See the full article here .

    Please help promote STEM in your local schools.

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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 10:11 am on May 23, 2016 Permalink | Reply
    Tags: , , , , NASA Chandra   

    From Daily Galaxy: “”Attempt No Journey There” –Swarm of 10,000 Black Holes and Neutron Stars Orbit Milky Way’s Supermassive Black Hole” 

    Daily Galaxy
    The Daily Galaxy

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    No image caption, no image credit

    May 22, 2016

    “The giant black holes in the cores of galaxies, a million to 20 billion times heavier than the Sun, therefore, cannot have been born in the death of a star. They must have formed in some other way, perhaps by the agglomeration of many smaller black holes; perhaps by the collapse of massive clouds of gas.” ― Kip S. Thorne, The Science of Interstellar.

    “The Center of our Milky Way Galaxy is a place of extremes,” says Mark Morris, an expert on The Galactic Center at UCLA. “For every star in our nighttime sky, for example, there would be a million for someone looking up from a planet near the Galactic center.”

    Thinking about a far-future visit to our galaxy’s central zone, brings to mind Arthur C. Clark’s admonition about a visit to Jupiter’s ocean moon, Europa –“All These Worlds are Yours –Except Europa Attempt No Landing There.” In addition to the extreme star density, a swarm of 10,000 or more black holes may be orbiting the Milky Way’s supermassive black hole, according to observations from NASA’s Chandra X-ray Observatory in 2015.

    Sag A*  NASA Chandra X-Ray Observatory 23 July 2014, the supermassive black hole at the center of the Milky Way
    Sag A* NASA Chandra X-Ray Observatory 23 July 2014, the supermassive black hole at the center of the Milky Way”

    This would represent the highest concentration of black holes anywhere in the Galaxy. These relatively small, stellar-mass black holes, along with neutron stars, appear to have migrated into the Galactic Center over the course of several billion years. Could this migration be the prelude to feeding our supermassive black hole suggested by Caltech’s Kip Thorne?

    The discovery was made as part of Chandra’s ongoing program of monitoring the region around Sagittarius A* (Sgr A*), the supermassive black hole at the center of the Milky Way, reported by by Michael Muno of the University of California, Los Angeles (UCLA) at a 2015 meeting of the American Astronomical Society.

    Among the thousands of X-ray sources detected within 70 light years of Sgr A*, Muno and his colleagues searched for those most likely to be active black holes and neutron stars by selecting only the brightest sources that also exhibited large variations in their X-ray output. These characteristics identify black holes and neutron stars that are in binary star systems and are pulling matter from nearby companion stars. Of the seven sources that met these criteria, four are within three light years of Sgr A*.

    “Although the region around Sgr A* is crowded with stars, we expected that there was only a 20 percent chance that we would find even one X-ray binary within a three-light-year radius,” said Muno. “The observed high concentration of these sources implies that a huge number of black holes and neutron stars have gathered in the center of the Galaxy.”

    Mark Morris, also of UCLA and a coauthor on the present work, had predicted a decade ago that a process called dynamical friction would cause stellar black holes to sink toward the center of the Galaxy. Black holes are formed as remnants of the explosions of massive stars and have masses of about 10 suns. As black holes orbit the center of the Galaxy at a distance of several light years, they pull on surrounding stars, which pull back on the black holes.

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    Unidentified. No image credit.

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    The images above are part of a Chandra program that monitors a region around the Milky Way’s supermassive black hole, Sagittarius A* (Sgr A*). Four bright, variable X-ray sources (circles) were discovered within 3 light years of Sgr A* (the bright source just above Source C). The lower panel illustrates the strong variability of one of these sources. This variability, which is present in all the sources, is indicative of an X-ray binary system where a black hole or neutron star is pulling matter from a nearby companion star.

    “Stars are packed quite close together in the center zone,” says Morris. “Then, there’s that supermassive black hole that is sitting in there, relatively quiet for now, but occasionally producing a dramatic outpouring of energy. The UCLA Galactic center group been use the Keck Telescopes in Hawaii to follow its activity for the last 17 years, watching not only the fluctuating emission from the black hole, but also watching the stars around it as they rapidly orbit the black hole.”

    Morris had predicted a decade ago that a process called dynamical friction would cause stellar black holes to sink toward the center of the Galaxy. Black holes are formed as remnants of the explosions of massive stars and have masses of about 10 suns. As black holes orbit the center of the Galaxy at a distance of several light years, they pull on surrounding stars, which pull back on the black holes. The net effect is that black holes spiral inward, and the low-mass stars move out. From the estimated number of stars and black holes in the Galactic Center region, dynamical friction is expected to produce a dense swarm of 20,000 black holes within three light years of Sgr A*. A similar effect is at work for neutron stars, but to a lesser extent because they have a lower mass.

    Once black holes are concentrated near Sgr A*, they will have numerous close encounters with normal stars there, some of which are in binary star systems. The intense gravity of a black hole can induce an ordinary star to “change partners” and pair up with the black hole while ejecting its companion. This process and a similar one for neutron stars are expected to produce several hundreds of black hole and neutron star binary systems.

    The black holes and neutron stars in the cluster are expected to gradually be swallowed by the supermassive black hole, Sgr A*, at a rate of about one every million years. At this rate, about 10,000 black holes and neutron stars would have been captured in a few billion years, adding about 3 percent to the mass of the central supermassive black hole, which is currently estimated to contain the mass of 3.7 million suns.

    In the meantime, the acceleration of low-mass stars by black holes will eject low-mass stars from the central region. This expulsion will reduce the likelihood that normal stars will be captured by the central supermassive black hole. This may explain why the central regions of some galaxies, including the Milky Way, are fairly quiet even though they contain a supermassive black hole.

    See the full article here .

    Please help promote STEM in your local schools

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  • richardmitnick 8:03 pm on May 12, 2016 Permalink | Reply
    Tags: , , NASA Chandra, Tycho Supernova Remnant   

    From Chandra: Tycho’s Supernova Remnant from Chandra 

    NASA Chandra Banner

    NASA Chandra Telescope

    NASA Chandra

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    Credit X-ray: NASA/CXC/GSFC/B.Williams et al; Optical: DSS
    Release Date May 12, 2016

    For the first time, a movie has been made of the evolution of Tycho’s supernova remnant.

    This sequence includes X-rays observations from Chandra spaced out over a decade and a half.

    Tycho belongs to a class of supernovas used to measure the expansion of the Universe so the details of these explosions are very important.

    By combining the Chandra data with 30 years worth of observations with the VLA, scientists have learned new things about this remnant and its history.


    Access mp4 video here .
    Video released in 2011

    When the star that created this supernova remnant exploded in 1572, it was so bright that it was visible during the day. And though he wasn’t the first or only person to observe this stellar spectacle, the Danish astronomer Tycho Brahe wrote a book about his extensive observations of the event, gaining the honor of it being named after him.

    In modern times, astronomers have observed the debris field from this explosion – what is now known as Tycho’s supernova remnant – using data from NASA’s Chandra X-ray Observatory, the NSF’s Karl G. Jansky Very Large Array (VLA) and many other telescopes.

    NRAO/VLA, on the Plains of San Agustin fifty miles west of Socorro, New Mexico.
    NRAO/VLA, on the Plains of San Agustin fifty miles west of Socorro, New Mexico

    Today, they know that the Tycho remnant was created by the explosion of a white dwarf star, making it part of the so-called Type Ia class of supernovas used to track the expansion of the Universe.

    Since much of the material being flung out from the shattered star has been heated by shock waves – similar to sonic booms from supersonic planes – passing through it, the remnant glows strongly in X-ray light. Astronomers have now used Chandra observations from 2000 through 2015 to create the longest movie of the Tycho remnant’s X-ray evolution over time, using five different images. This shows the expansion from the explosion is still continuing about 450 years later, as seen from Earth’s vantage point roughly 10,000 light years away.

    By combining the X-ray data with some 30 years of observations in radio waves with the VLA, astronomers have also produced a movie, using three different images. Astronomers have used these X-ray and radio data to learn new things about this supernova and its remnant.

    The researchers measured the speed of the blast wave at many different locations around the remnant. The large size of the remnant enables this motion to be measured with relatively high precision. Although the remnant is approximately circular, there are clear differences in the speed of the blast wave in different regions. The speed in the right and lower right directions is about twice as large as that in the left and the upper left directions. This difference was also seen in earlier observations.

    This range in speed of the blast wave’s outward motion is caused by differences in the density of gas surrounding the supernova remnant. This causes an offset in position of the explosion site from the geometric center, determined by locating the center of the circular remnant. The astronomers found that the size of the offset is about 10% of the remnant’s current radius, towards the upper left of the geometric center. The team also found that the maximum speed of the blast wave is about 12 million miles per hour.

    Offsets such as this between the explosion center and the geometric center could exist in other supernova remnants. Understanding the location of the explosion center for Type Ia supernovas is important because it narrows the search region for a surviving companion star. Any surviving companion star would help identify the trigger mechanism for the supernova, showing that the white dwarf pulled material from the companion star until it reached a critical mass and exploded. The lack of a companion star would favor the other main trigger mechanism, where two white dwarfs merge causing the critical mass to be exceeded, leaving no star behind.

    The significant offset from the center of the explosion to the remnant’s geometric center is a relatively recent phenomenon. For the first few hundred years of the remnant, the explosion’s shock was so powerful that the density of gas it was running into did not affect its motion. The density discrepancy from the left side to the right has increased as the shock moved outwards, causing the offset in position between the explosion center and the geometric center to grow with time. So, if future X-ray astronomers, say 1,000 years from now, do the same observation, they should find a much larger offset.

    A paper* describing these results has been accepted for publication in The Astrophysical Journal Letters and is available online*. The authors are Brian Williams (NASA’s Goddard Space Flight Center), Laura Chomiuk (Michigan State University), John Hewitt (University of North Florida), John Blondin (North Carolina State University), Kazimierz Borkowski (NCSU), Parviz Ghavamian (Towson University), Robert Petre (GSFC), and Stephen Reynolds (NCSU).

    *Science paper:
    An X-ray and Radio Study of the Varying Expansion Velocities in Tycho’s Supernova Remnant

    See the full article here .

    Please help promote STEM in your local schools.

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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 8:38 pm on April 28, 2016 Permalink | Reply
    Tags: , , NASA Chandra, Probing Dark Energy with Clusters   

    From Chandra: “Probing Dark Energy with Clusters: ‘Russian Doll’ Galaxy Clusters Reveal Information About Dark Energy” 

    NASA Chandra Banner

    NASA Chandra Telescope

    NASA Chandra

    April 28, 2016

    1
    Composite

    2
    X-ray

    3
    Optical

    Fast Facts for Abell 1835:
    Credit X-ray: NASA/CXC/Univ. of Alabama/A. Morandi et al; Optical: SDSS, NASA/STScI
    Release Date April 28, 2016
    Observation Dates 7 Dec 2005, 24 Jul and 25 Aug 2006

    Fast Facts for MS 1455.0+2232:
    Credit X-ray: NASA/CXC/Univ. of Alabama/A. Morandi et al; Optical: SDSS, NASA/STScI
    Release Date April 28, 2016
    Observation Dates 19 May 2000, 05 Sep 2003, 23 Mar 2007

    Fast Facts for RXJ 1347.5-1145:
    Credit X-ray: NASA/CXC/Univ. of Alabama/A. Morandi et al; Optical: SDSS, NASA/STScI
    Release Date April 28, 2016
    Observation Dates 3 Sep 2003, 16 Mar, 14 May and 11 Dec 2012

    Fast Facts for ZWCL 3146:
    Credit X-ray: NASA/CXC/Univ. of Alabama/A. Morandi et al; Optical: SDSS, NASA/STScI
    Release Date April 28, 2016
    Observation Dates 10 May 2000, 18 Jan 2008

    Researchers are using a large sample of galaxy cluster to investigate dark energy.

    The details of X-ray emission from over 300 galaxy clusters were obtained with Chandra.

    The galaxy clusters range in distance from about 760 million to 8.7 billion light years from Earth.

    The study shows that dark energy has not changed over billions of years.

    These four galaxy clusters were part of a large survey of over 300 clusters used to investigate dark energy, the mysterious energy that is currently driving the accelerating expansion of the Universe, as described in our latest press release. In these composite images, X-rays from NASA’s Chandra X-ray Observatory (purple) have been combined with optical light from the Hubble Space Telescope and Sloan Digital Sky Survey (red, green, and blue).

    NASA/ESA Hubble Telescope
    NASA/ESA Hubble Telescope

    SDSS Telescope at Apache Point, NM, USA
    SDSS Telescope at Apache Point, NM, USA

    Researchers used a novel technique that takes advantage of the observation that the outer reaches of galaxy clusters, the largest structures in the universe held together by gravity, show similarity in their X-ray emission profiles and sizes. That is, more massive clusters are simply scaled up versions of less massive ones, similar to Russian dolls that nest inside one another.

    The amount of matter in the Universe, which is dominated by the unseen substance called dark matter, and the properties of dark energy (what astronomers call cosmological parameters) affect the rate of expansion of the Universe and, therefore, how the distances to objects change with time. If the cosmological parameters used are incorrect and a cluster is inferred to be traveling away faster than the correct value, then a cluster will appear to be larger and fainter due to this “Russian doll” property. If the cluster is inferred to be traveling away more slowly than the correct value, the cluster will be smaller and brighter than a cluster according to theory.

    These latest results confirm earlier studies that the amount of dark energy has not changed over billions of years. They also support the idea that dark energy is best explained by the “cosmological constant,” which Einstein first proposed and is equivalent to the energy of empty space.

    The galaxy clusters in this large sample ranged in distance from about 760 million to 8.7 billion light years from Earth, providing astronomers with information about the era where dark energy caused the once-decelerating expansion of the Universe to accelerate.

    The X-ray emission in the outer parts of galaxy clusters is faint because the gas is diffuse there. To deal with this issue in this study, the X-ray signal from different clusters was added together. Regions near the centers of the clusters are excluded from the analysis because of large differences between the properties of different clusters caused by supermassive black hole outbursts, the cooling of gas and the formation of stars.

    A paper describing these results by Andrea Morandi and Ming Sun (University of Alabama at Huntsville) appeared in the April 11th, 2016 issue of the Monthly Notices of the Royal Astronomical Society journal and is available online*.

    *Science paper:
    Probing dark energy via galaxy cluster outskirts

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

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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.

     
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