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  • richardmitnick 9:00 am on June 5, 2017 Permalink | Reply
    Tags: , , , , , G292.0+1.8, , Supernovae   

    From Chandra via Manu Garcia: “G292.0+1.8: Stellar Forensics with Striking Image from Chandra” 

    NASA Chandra Telescope

    NASA Chandra

    Via Manu Garcia

    Manu Garcia, a friend from IAC.

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    Credit: X-ray: NASA/CXC/Penn State/S.Park et al.; Optical: Pal.Obs. DSS

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    Calteh Palomar Observatory in San Diego County, California, United States

    The aftermath of the death of a massive star is shown in beautiful detail in this new composite image of G292.0+1.8. In color is the Chandra X-ray Observatory image – easily the deepest X-ray image ever obtained of this supernova remnant – and in white is optical data from the Digitized Sky Survey. Although considered a “textbook” case of a supernova remnant, the intricate structure shown here reveals a few surprises.

    Near the center of G292.0+1.8 is the so-called pulsar wind nebula, most easily seen in high energy X-rays. This is the magnetized bubble of high-energy particles that surrounds the “pulsar”, a rapidly rotating neutron star that remained behind after the original, massive star exploded. The narrow, jet-like feature running from north to south in the image is likely parallel to the spin axis of the pulsar.

    The pulsar is located slightly below and to the left of the center of G292.0+1.8. Assuming that the pulsar was born at the center of the remnant, it is thought that recoil from the lopsided explosion may have kicked the pulsar in this direction. However, the kick direction and the pulsar spin direction do not appear to be aligned, in contrast to apparent spin-kick alignments seen in some other supernova remnants.

    Another key feature of this remnant is the long white line running from left to right across the center called the equatorial belt. This structure is thought to be created when the star – before it died – expelled material from around its equator via winds. The orientation of the equatorial belt suggests the parent star maintained the same spin axis both before and after it exploded.

    One puzzling aspect of the image is the lack of evidence for thin filaments of high energy X-ray emission, thought to be an important site for cosmic ray acceleration in supernova remnants. These filaments are seen in other supernova remnants such as Cassiopeia A, Tycho and Kepler. One explanation may be that efficient acceleration occurs primarily in very early stages of supernova remnant evolution, and G292.0+1.8, with an estimated age of several thousand years, is too old to show these effects. Casseiopeia A, Tycho and Kepler, with ages of several hundred years, are much younger.

    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 11:12 am on May 28, 2017 Permalink | Reply
    Tags: , , , , , Supernovae,   

    From ANU: “ANU invites everyone to join the search for exploding stars” 

    ANU Australian National University Bloc

    Australian National University

    Will Wright
    +61 2 6125 7979
    media@anu.edu.au

    ANU is inviting everyone with an interest in astronomy to join a search that the University is leading for exploding stars called supernovae.

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    At left, the recently taken image featuring a newly appeared dot of light; in the middle, the old reference image taken a few years ago; at right, the difference between the two images revealing the new supernova.
    Credit: ANU

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    Citizen scientists combed through data from ANU Siding Spring Observatory to identify a Type Ia supernova, like the one depicted in this artist’s impression, that exploded hundreds of millions of years before dinosaurs roamed the Earth. Credit: ESA

    Astrophysicists use supernovae, which are explosions as bright as 100 million billion billion billion lightning bolts, as light sources to measure the Universe and acceleration of its growth.

    Co-lead researcher ANU astrophysicist Dr Brad Tucker said scientists can measure the distance of a supernova from Earth by calculating how much the light from the exploding star fades.

    “Using exploding stars as markers all across the Universe, we can measure how the Universe is growing and what it’s doing,” said Dr Tucker from the ANU Research School of Astronomy and Astrophysics.

    “We can then use that information to better understand dark energy, the cause of the Universe’s acceleration.”

    The ANU project will allow citizen scientists to use a web portal on Zooniverse.org to search images taken by the SkyMapper telescope at the ANU Siding Spring Observatory for the SkyMapper Transient Survey.


    ANU Skymapper telescope, a fully automated 1.35 m (4.4 ft) wide-angle optical telescope, at Siding Spring Observatory , near Coonabarabran, New South Wales, Australia

    Siding Spring Observatory near Coonabarabran, New South Wales, Australia

    Dr Tucker said finding supernovae involved citizen volunteers scanning the SkyMapper images online to look for differences and marking up those differences for the researchers to follow up.

    “With the power of the people, we can check these images in minutes and get another telescope to follow up,” he said.

    Dr Tucker said citizen science was an emerging and increasingly important field that bridged the gap between scientific research and public engagement.

    “Thousands of passionate people can achieve things that would take scientists working alone years to do,” he said.

    Co-lead researcher Dr Anais Möller said SkyMapper is taking thousands of new images of the southern sky every month for the supernova search project.

    “The first people who identify an object that turns out to be a supernova will be publicly recognised as co-discoverers,” said Dr Möller from the ANU Research School of Astronomy and Astrophysics.

    “SkyMapper is the only telescope that is doing a comprehensive survey of the southern sky looking for supernovae and other interesting transient events at these distances.

    “We are examining an area 10,000 times larger than the full moon every week. As well as finding Type Ia supernovae, which we use to measure how the Universe is expanding, we will also find other types of supernovae that change in brightness with time – ranging from a couple of weeks to months.

    “If we discover supernovae early we have a good chance of understanding them, as well as having better measurements for the expansion of the Universe.”

    SkyMapper is a 1.3-metre telescope that is creating a full record of the southern sky for astronomers.

    People can to participate in the ANU citizen science project at http://www.zooniverse.org/projects/skymap/supernova-sighting to join the search for exploding stars.

    See the full article here .

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    ANU Campus

    ANU is a world-leading university in Australia’s capital city, Canberra. Our location points to our unique history, ties to the Australian Government and special standing as a resource for the Australian people.

    Our focus on research as an asset, and an approach to education, ensures our graduates are in demand the world-over for their abilities to understand, and apply vision and creativity to addressing complex contemporary challenges.

     
  • richardmitnick 12:37 pm on May 14, 2017 Permalink | Reply
    Tags: , , , Supernovae, What’s a safe distance between us and a supernova?   

    From EarthSky: “What’s a safe distance between us and a supernova?” 

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    EarthSky

    May 7, 2017
    EarthSky

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    Artist’s illusration of a supernova, or exploding star, via http://SmithsonianScience.org

    A supernova is a star explosion – destructive on a scale almost beyond human imagining. If our sun exploded as a supernova, the resulting shock wave probably wouldn’t destroy the whole Earth, but the side of Earth facing the sun would boil away. Scientists estimate that the planet as a whole would increase in temperature to roughly 15 times hotter than our normal sun’s surface. What’s more, Earth wouldn’t stay put in orbit. The sudden decrease in the sun’s mass might free the planet to wander off into space. Clearly, the sun’s distance – 8 light-minutes away – isn’t safe. Fortunately, our sun isn’t the sort of star destined to explode as a supernova. But other stars, beyond our solar system, will. What is the closest safe distance? Scientific literature cites 50 to 100 years as the closest safe distance between Earth and a supernova. Follow the links below to learn more.

    What would happen if a supernova exploded near Earth?

    How many potential supernovae are located closer to us than 50 to 100 light-years?

    What about Betelgeuse?

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    Betelgeuse and Bellatrix: Orion’s Shoulders

    How often do supernovae erupt in our galaxy?

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    This image shows the remnant of Supernova 1987A seen in light of very different wavelengths. ALMA data (in red) shows newly formed dust in the centre of the remnant. Hubble (in green) and Chandra (in blue) data show the expanding shock wave.
    Date 6 January 2014
    Source http://www.eso.org/public/images/eso1401a/
    Author ALMA (ESO/NAOJ/NRAO)/A. Angelich. Visible light image: the NASA/ESA Hubble Space Telescope. X-Ray image: The NASA Chandra X-Ray Observatory

    NASA/ESA Hubble Telescope

    NASA/Chandra Telescope

    What would happen if a supernova exploded near Earth? Let’s consider the explosion of a star besides our sun, but still at an unsafe distance. Say, the supernova is 30 light-years away. Dr. Mark Reid, a senior astronomer at the Harvard-Smithsonian Center for Astrophysics, has said:

    “… were a supernova to go off within about 30 light-years of us, that would lead to major effects on the Earth, possibly mass extinctions. X-rays and more energetic gamma-rays from the supernova could destroy the ozone layer that protects us from solar ultraviolet rays. It also could ionize nitrogen and oxygen in the atmosphere, leading to the formation of large amounts of smog-like nitrous oxide in the atmosphere.”

    What’s more, if a supernova exploded within 30 light-years, phytoplankton and reef communities would be particularly affected. Such an event severely deplete the base of the ocean food chain.

    Suppose the explosion were slightly more distant. An explosion of a nearby star might leave Earth and its surface and ocean life relatively intact. But any relatively nearby explosion would still shower us with gamma rays and other high-energy radiation. This radiation could cause mutations in earthly life. Also, the radiation from a nearby supernova could change our climate.

    No supernova has been known to erupt at this close distance in the known history of humankind. The most recent supernova visible to the eye was Supernova 1987A, in the year 1987. It was approximately 168,000 light-years away.

    Before that, the last supernova visible to the eye was was documented by Johannes Kepler in 1604. At about 20,000 light years, it shone more brightly than any star in the night sky. It was even visible in daylight! But it didn’t cause earthly effects, as far as we know.

    How many potential supernovae are located closer to us than 50 to 100 light-years? The answer depends on the kind of supernova.

    A Type II supernova is an aging massive star that collapses. There are no stars massive enough to do this located within 50 light-years of Earth.

    But there are also Type I supernovae – caused by the collapse of a small faint white dwarf star. These stars are dim and hard to find, so we can’t be sure just how many are around. There are probably a few hundred of these stars within 50 light-years.

    The star IK Pegasi B is the nearest known supernova progenitor candidate. It’s part of a binary star system, located about 150 light years from our sun and solar system.

    The main star in the system – IK Pegasi A – is an ordinary main sequence star, not unlike our sun. The potential Type I supernova is the other star – IK Pegasi B – a massive white dwarf that’s extremely small and dense. When the A star begins to evolve into a red giant, it’s expected to grow to a radius where the white dwarf can accrete, or take on, matter from A’s expanded gaseous envelope. When the B star gets massive enough, it might collapse on itself, in the process exploding as a supernova.

    What about Betelgeuse? Another star often mentioned in the supernova story is Betelgeuse, one of the brightest stars in our sky, part of the famous constellation Orion. Betelgeuse is a supergiant star. It is intrinsically very brilliant.

    Such brilliance comes at a price, however. Betelgeuse is one of the most famous stars in the sky because it’s due to explode someday. Betelgeuse’s enormous energy requires that the fuel be expended quickly (relatively speaking), and in fact Betelgeuse is now near the end of its lifetime. Someday soon (astronomically speaking), it will run out of fuel, collapse under its own weight, and then rebound in a spectacular Type II supernova explosion. When this happens, Betelgeuse will brighten enormously for a few weeks or months, perhaps as bright as the full moon and visible in broad daylight.

    When will it happen? Probably not in our lifetimes, but no one really knowns. It could be tomorrow or a million years in the future. When it does happen, any beings on Earth will witness a spectacular event in the night sky, but earthly life won’t be harmed. That’s because Betelgeuse is 430 light-years away. Read more about Betelgeuse as a supernova.

    How often do supernovae erupt in our galaxy? No one knows. Scientists have speculated that the high-energy radiation from supernovae has already caused mutations in earthly species, maybe even human beings.

    One estimate suggests there might be one dangerous supernova event in Earth’s vicinity every 15 million years. Another says that, on average, a supernova explosion occurs within 10 parsecs (33 light-years) of the Earth every 240 million years. So you see we really don’t know. But you can contrast those numbers to a few million years for the time humans are thought to have existed on the planet – and four-and-a-half billion years for the age of Earth itself.

    And, if you do that, you’ll see that a supernova is certain to occur near Earth – but probably not in the foreseeable future of humanity.

    Bottom line: Scientific literature cites 50 to 100 years as the closest safe distance between Earth and a supernova.

    See the full article here .

    See the full article <a href="http://1 EarthSky See the full article here . Please help promote STEM in your local schools. STEM Icon Stem Education Coalition

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  • richardmitnick 4:08 pm on May 8, 2017 Permalink | Reply
    Tags: , , , , , , , Supernovae   

    From Many Worlds: “Supernovae Give, And Can Take Away” 

    NASA NExSS bloc

    NASA NExSS

    Many Words icon

    Many Worlds

    2017-05-08
    Marc Kaufman

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    What is likely the brightest supernova in recorded human history, SN 1006 lit up planet Earth’s sky in the year 1006 AD. The expanding debris cloud from the stellar explosion, still puts on a cosmic light show across the electromagnetic spectrum. The supernova is located about 7,000 light-years from Earth, meaning that its thermonuclear explosion actually happened 7,000 years before the Earth. Shockwaves in the remnant accelerate particles to extreme energies and are thought to be a source of the mysterious cosmic rays. NASA, ESA, Zolt Levay (STScI)

    We live in a dangerous universe. We know about meteor and comets, about harmful radiation that could extinguish life without an electromagnetic shield, about major changes in climate that are both natural and man-made.

    Magnetosphere of Earth, original bitmap from NASA. SVG rendering by Aaron Kaase

    There’s another risk out there that some scientists assert could cause large-scale extinctions even though it would occur scores of light-years away. These are supernovae – explosions of massive stars that both create and spread the heavy elements needed for life and send out high energy cosmic rays that can travel far and cause enormous damage.

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    http://hyperphysics.phy-astr.gsu.edu/hbase/Astro/snovcn.html

    As with most of these potential threats, they fortunately occur on geological or astronomical time scales rather than human ones. But that doesn’t mean they don’t happen.

    At the recent Astrobiology Science Conference (AbSciCon) a series of talks focused on that last threat – starting with a talk on “When Stars Attack.”

    And together five different presenters made a persuasive case that Earth was on the receiving end of a distant supernova explosion some two to three million years ago, and probably around 7 or 8 million years ago as well. The effects of the cosmic ray bombardment have been debated and disputed, but the evidence for the occurrences is based on the rock record and is now strong.

    “The evidence is there on the ocean floor, in rocks, nodules and sediment,” said Brian Fields, professor of astronomy at University of Illinois. “We’ve been able to date it and provide some idea of how far away the star blew up.” The answer is between about 90 and 300 light-years.

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    Supernova 1994D exploded on the outskirts of disk galaxy, and outshines even the center of the galaxy. Supernovae may expel much, if not all, of the material away from a star, at velocities up to 30,000 km/s or 10% of the speed of light. This drives an expanding and fast-moving shock wave into the surrounding interstellar medium that, if close to Earth (or any other planet) can have dire consequences. Supernovae also create, fuse and eject the bulk of the chemical elements produced by nucleosynthesis, the heavier elements needed to form planets and later make possible life. ( High-Z Supernova Search Team, HST, NASA)

    “Supernova explosions happen all the time– on average every 30 years in our galaxy, though they are most often obscured from view,” Fields said. “They generate cosmic rays that can spread through the galaxy for 100 million years. These are the cosmic rays that make carbon-14 and can threaten astronauts in space. But that’s not what we’re focused on — we look at the ones that are close to us and could have a far more dramatic effect, and they are pretty rare.”

    HESS Cherenko Array, searching for cosmic rays, located on the Cranz family farm, Göllschau, in Namibia, near the Gamsberg

    What is deemed to be the “kill zone” for a planet nearby a supernova is 30 light-years; the high energy particles from an explosion that close would, he said, likely end all or most life on Earth by setting into motion a variety of atmospheric and surface changes. Fields there is no evidence of such a close and damaging supernove within the past 10 million years, the period that has been studied with some rigor.

    But because a close supernova explosion hasn’t happened recently doesn’t mean that it didn’t happened during earlier times. Or that it couldn’t happen in the far future.

    “By nailing the signal of a close but not ‘kill zone’ supernova two to three million years ago, and most likely another at 7 to 8 million years ago, we make the case that supernova can and do have significant effects on Earth.”

    The community of scientists who study supernovae and their effects on Earth, both potential and known, is small, and has been most active in the past decade. There was an earlier time when scientists focused on supernovae as the potential cause for the massive dinosaur extinction, but the field shrank with confirmation in 1990 that a six-mile wide meteor landed on Mexico’s Yucatan Peninsula about million years ago and was the likely cause of the global extinction.

    But now, with the advent of new theories and some very high tech and precise measuring the field and subject has come to life, with research nodes in Germany, Australia and the American Midwest.

    The key to understanding the effects of distant supernovae on Earth involves a radioactive isotope of iron, iron-60.

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    Nailing the half-life of iron-60, http://physicsworld.com/cws/article/news/2015/jan/30/nailing-the-half-life-of-iron-60

    It’s one of the many elements known to be sent into the cosmos by the massive thermonuclear blasts that define a supernova, that send out shock waves capable of spurring the formation of new stars as well as providing the universe with the heavier chemical elements needed to form everything from planets to genes.

    It was the young Fields and colleagues who theorized some two decades ago that iron-60 could be a telltale sign of a relatively nearby supernova. He told me that no other sources of iron 60 are known to exist, and so if it were found on Earth scientists would know where it came from.

    With a half-life of some three million years, the iron-60 would be a potentially strong signal for that length of time and and then a weaker but potentially detectable signal after that.

    The question was how do you find iron-60 on Earth? The answer came from the bottom of the ocean.

    First in 1999 a group from the Technical University of Munich [TUM] in Germany identified some iron-60 in iron-manganese crustal rocks at the bottom of the Pacific, and then last year an overlapping group from the Technical University of Berlin reported finding the telltale isotope in not only rocks but also in nodules and most important in sea-floor sediments. They used ultra-sensitive accelerator mass spectrometry to isolate and identify the iron-60, which they reported was deposited some 1.6 to 3 million years ago.

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    Accelerator mass spectrometer at Lawrence Livermore National Laboratory
    “The 1 MV accelerator mass spectrometer was (see photo) developed partially under the Resource funding. 14C and tritium analyses of biomedical samples submitted by Resource users are conducted using this 1 MV system. The AMS spectrometer consists of a cesium sputter source, low-energy injection beam line, the high voltage collision cell (accelerator), a high-energy mass spectrometer and a particle detector for energy measurements (proceeding clockwise from lower left in the photograph).”
    Source http://bioams.llnl.gov/equipment.php

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    These are transmission electron microscope images showing tiny magnetofossils containing iron-60, a form of iron produced during the violent explosion and death of a massive star in a supernova. They were deposited by bacteria in sediments found on the floor of the Pacific Ocean.© Marianne Hanzlik, Chemie Department, FG Elektronenmikroskopie, Technische Universität München

    Last year as well the Australian group, led by Anton Wallner of the Australian National University, found the iron-60 to be deposited globally and to have arrived within the same general time frame. And Gunther Korschinek, a physicist at the Technical University of Munich involved in the initial German iron-60 detections, led a team that found elevated amounts of iron-60 in moon rocks returned to Earth during the Apollo program.

    As Fields put it, the studies together gave a clear signal of a supernova explosion, or series of explosions, at 2 to 3 million years ago, and a less clear but likely signal of the same at 7 to 8 million years ago.

    Since Fields and other scientists were presenting during the AbSciCon conference, the talks not surprisingly focused on potential biological implications of supernova explosions. And while supernova impacts on the biosphere are not particularly well understood, a number of intriguing theories were presented.

    Brian Thomas of Washburn University described how cosmic rays from close supernova would significantly increase levels of electrically charged elements and molecules in the atmosphere, lasting thousands of years. In the upper atmosphere this would have the effect of setting into motion a chemical cascade that would deplete stratospheric ozone. In the lower atmosphere, the effect would likely be changes in climate and minor mass extinctions.

    The “holy grail” of their supernova work is matching a detected one with a dramatic event in the Earth biosphere, most especially a mass extinction. The 2 to 3 million years ago period includes the boundary between the Pleistocene and Pliocene epochs, when Earth climate changed and major glaciations periods began — possibly supernova-related changes but not the extreme change a close supernova could produce.

    Another potential effect of the supernova event of 2 to 3 million years ago is increased rates of mutation and of lightning, and thus forest fires on Earth.

    Adrian Merlott of the University of Kansas suggested that expected mutations from radiation sources such as supernovae could explain evolutionary changes in a variety of groups of organisms and creatures during that period — as a result of increased deadly cancers in some species and increased positive mutations in others.

    He also said that evidence of more widespread wildfires during that long period — as measured in charcoal deposits — could be the result of increased cloud to ground lightning induced by the additional high-energy particle environment created by a relatively close supernova explosion.

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    The Crab nebula – one of the most glorious images produced by the Hubble Space Telescope — is the remnant of supernovae explosions that occurred at a distance of some 6,700 light-years. The very bright light of the explosion was noted in 1054 and remained visible for around two years. The event was recorded in contemporary Chinese astronomy, and references to it are also found in a later (13th-century) Japanese document, perhaps in pictograph associated with the Anasazi people of the Southwest. The supernova, SN 1054 has been widely studied and is often considered the best known supernova in astronomy. (NASA).

    The iron-60 signatures of a close supernova have been a great boon to the field, but they do not go back beyond that almost 10 million year period when the radioactivity was present. To go back further than that, Fields said different radioactive signatures would be needed — and not those that go back to the formation of the planet.

    “It’s a hard problem because nature has been unkind,” he said. “The early mass extinctions – 100 million and more years ago – need radioactivity that lasts that long. And the only element we’ve found is plutonium-244, which is not stable in any form.”

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    http://www.alamy.com/stock-photo/plutonium-244.html

    Plutonium-244 has a half life of 80 million years, and so could potentially be used to identify close supernova explosions in a manner similar to iron-60, but during that much longer time frame. And as Fields explained it, plutonium-244 is produced in only two ways: during the explosion of a nuclear bomb or the explosion of a supernovae.

    Although the science around the formation and detection of plutonium-244 in nature is immature, he said it remains the best pathway to find that “holy grail” — a known mass extinction directly associated with a close supernova explosion.

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    Supernovae can burn with a luminosity of ten billion suns. This show a before and after for supernova 1987A, which exploded in 1987 in the Large Magellanic Cloud (LMC), a nearby galaxy. (Australian Astronomical Observatory/ David Malin)

    See the full article here .

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    About Many Worlds

    There are many worlds out there waiting to fire your imagination.

    Marc Kaufman is an experienced journalist, having spent three decades at The Washington Post and The Philadelphia Inquirer, and is the author of two books on searching for life and planetary habitability. While the “Many Worlds” column is supported by the Lunar Planetary Institute/USRA and informed by NASA’s NExSS initiative, any opinions expressed are the author’s alone.

    This site is for everyone interested in the burgeoning field of exoplanet detection and research, from the general public to scientists in the field. It will present columns, news stories and in-depth features, as well as the work of guest writers.

    About NExSS

    The Nexus for Exoplanet System Science (NExSS) is a NASA research coordination network dedicated to the study of planetary habitability. The goals of NExSS are to investigate the diversity of exoplanets and to learn how their history, geology, and climate interact to create the conditions for life. NExSS investigators also strive to put planets into an architectural context — as solar systems built over the eons through dynamical processes and sculpted by stars. Based on our understanding of our own solar system and habitable planet Earth, researchers in the network aim to identify where habitable niches are most likely to occur, which planets are most likely to be habitable. Leveraging current NASA investments in research and missions, NExSS will accelerate the discovery and characterization of other potentially life-bearing worlds in the galaxy, using a systems science approach.
    The National Aeronautics and Space Administration (NASA) is the agency of the United States government that is responsible for the nation’s civilian space program and for aeronautics and aerospace research.

    President Dwight D. Eisenhower established the National Aeronautics and Space Administration (NASA) in 1958 with a distinctly civilian (rather than military) orientation encouraging peaceful applications in space science. The National Aeronautics and Space Act was passed on July 29, 1958, disestablishing NASA’s predecessor, the National Advisory Committee for Aeronautics (NACA). The new agency became operational on October 1, 1958.

    Since that time, most U.S. space exploration efforts have been led by NASA, including the Apollo moon-landing missions, the Skylab space station, and later the Space Shuttle. Currently, NASA is supporting the International Space Station and is overseeing the development of the Orion Multi-Purpose Crew Vehicle and Commercial Crew vehicles. The agency is also responsible for the Launch Services Program (LSP) which provides oversight of launch operations and countdown management for unmanned NASA launches. Most recently, NASA announced a new Space Launch System that it said would take the agency’s astronauts farther into space than ever before and lay the cornerstone for future human space exploration efforts by the U.S.

    NASA science is focused on better understanding Earth through the Earth Observing System, advancing heliophysics through the efforts of the Science Mission Directorate’s Heliophysics Research Program, exploring bodies throughout the Solar System with advanced robotic missions such as New Horizons, and researching astrophysics topics, such as the Big Bang, through the Great Observatories [Hubble, Chandra, Spitzer, and associated programs. NASA shares data with various national and international organizations such as from the [JAXA]Greenhouse Gases Observing Satellite.

     
  • richardmitnick 10:35 am on April 21, 2017 Permalink | Reply
    Tags: , , Supernovae,   

    From COSMOS: “Sixteen ways of looking at a supernova” 

    Cosmos Magazine bloc

    COSMOS

    21 April 2017
    Andrew Masterson

    Thanks to fast thinking, luck, and gravitational lensing, four telescopes managed to observe a quadruple image of a single supernova. Andrew Masterson reports.

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    The light from the supernova iPTF16geu and of its host galaxy is warped and amplified by the curvature of space by the mass of a foreground galaxy.
    ALMA (ESO/NRAO/NAOJ), L. Calçada (ESO), Y. Hezaveh et al., edited and modified by Joel Johansson

    In September 2016, when astronomer Ariel Goobar and his colleagues at the Intermediate Palomar Transient Factory in California saw the image recorded by the facility’s field camera, they knew they had to move fast.

    Caltech Palomar Intermediate Palomar Transient Factory telescope at the Samuel Oschin Telescope at Palomar Observatory,located in San Diego County, California, United States

    They were looking at something that was simultaneously massive, spectacular, new, short-lived, and a triumphant demonstration of Einstein’s theory of general relativity.

    As reported in the journal Science, Goobar, from Stockholm University in Sweden, and his team had discovered a brand new Type 1a supernova, which they later dubbed iPTF16geu.

    Any freshly discovered supernova is a significant astronomical find, but in this case its importance was magnified – quite literally – by circumstance.

    Einstein’s theory of general relativity predicts that matter curves the spacetime surrounding it. The region of curved spacetime around a particularly massive object – a galaxy, say – can, if the alignment is correct, bend the paths of light travelling through it in such a way as to act as a lens, enlarging the appearance of objects in the distance behind it.

    The effect is known as “gravitational lensing” and is well known to astronomers.

    Gravitational Lensing NASA/ESA

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    From left: an image from the SDSS survey; a zoomed view showing the foreground lensing galaxy; two versions of the four resolved images of the supernova, resolved by the Hubble Space Telescope and the Keck/NIRC2 instrument. Joel Johansson

    Goobar’s team quickly realised that its view of iPTF16geu was an extreme example of the phenomenon. A galaxy situated between Earth and the supernova was magnifying the phenomenon by 50 times, providing an unparalleled view of the stellar explosion. They were also able to see four separate images of the supernova, each formed by light taking a different path around the galaxy.

    The light burst from a Type 1 supernova starts to fade precipitously after only a couple of minutes, and disappears pretty much completely after a year.

    Realising that the window of opportunity was limited and closing fast, the team hit the phones and did some rapid talking. In a very short period, three other big facilities homed in on iPTF16geu.

    As well as the initial Palomar shot, the astronomers captured images from the Hubble Telescope, the Very Large Telescope in Chile, and the Keck Observatory in Hawaii.

    NASA/ESA Hubble Telescope

    ESO/VLT at Cerro Paranal, with an elevation of 2,635 metres (8,645 ft) above sea level

    Keck Observatory, Mauna Kea, Hawaii, USA

    The results – multiple observations of multiple images of the supernova event – provide data that will offer insights not only into the supernova itself, but also into the structure of the intervening galaxy and the physics of gravitational lensing.

    See the full article here .

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  • richardmitnick 12:58 pm on March 30, 2017 Permalink | Reply
    Tags: , , , , , , Supernovae   

    From Hubble: “Search For Stellar Survivor of a Supernova Explosion ” Hubble-Europe and USA/HubbleSite 

    NASA Hubble Banner

    NASA/ESA Hubble Telescope

    NASA/ESA Hubble Telescope

    You-Hua Chu
    Institute of Astronomy and Astrophysics, Academia Sinica
    Taipei, Taiwan
    Tel: +886 2 2366 5300
    Email: yhchu@asiaa.sincia.edu.tw

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

    Christine Pulliam
    Space Telescope Science Institute, Baltimore, Maryland
    410-338-6437
    cpulliam@stsci.edu

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

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    A group of astronomers used Hubble to study the remnant of the Type Ia supernova explosion SNR 0509-68.7 — also known as N103B (seen at the top). The supernova remnant is located in the Large Magellanic Cloud, just over 160 000 light-years from Earth.

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    This ground-based image shows both the Small and the Large Magellanic Clouds — two satellite galaxies of the Milky Way. The Small Magellanic Cloud can be seen on the left, the Large Magellanic Cloud on the right. This photo was taken by the Japanese astrophotographer Akira Fujii.

    In contrast to many other Supernova remnants N103B does not appear to have a spherical shape but is strongly elliptical. Astronomers assume that part of material ejected by the explosion hit a denser cloud of interstellar material, which slowed its speed. The shell of expanding material being open to one side supports this idea.

    The relative proximity of N103B allows astronomers to study the life cycles of stars in another galaxy in great detail. And probably even to lift the veil on questions surrounding this type of supernova. The predictable luminosity of Type Ia supernovae means that astronomers can use them as cosmic standard candles to measure their distances, making them useful tools in studying the cosmos. Their exact nature, however, is still a matter of debate. Astronomers suspect Type Ia supernovae occur in binary systems in which at least one of the stars in the pair is a white dwarf [1].

    There are currently two main theories describing how these binary systems become supernovae. Studies like the one that has provided the new image of N103B — that involve searching for remnants of past explosions — can help astronomers to finally confirm one of the two theories.

    One theory assumes that both stars in the binary are white dwarfs. If the stars merge with one another it would ultimately lead to a supernova explosion of type Ia.

    The second theory proposes that only one star in the system is a white dwarf, while its companion is a normal star. In this theory material from the companion star is accreted onto the white dwarf until its mass reaches a limit, leading to a dramatic explosion. In that scenario, the theory indicates that the normal star should survive the blast in at least some form. However, to date no residual companion around any type Ia supernova has been found.

    Astronomers observed the N103B supernova remnant in a search for such a companion. They looked at the region in H-alpha — which highlights regions of gas ionised by the radiation from nearby stars — to locate supernova shock fronts. They hoped to find a star near the centre of the explosion which is indicated by the curved shock fronts. The discovery of a surviving companion would put an end to the ongoing discussion about the origin of type Ia supernova.

    And indeed they found one candidate star that meets the criteria — for star type, temperature, luminosity and distance from the centre of the original supernova explosion. This star has approximately the same mass as the Sun, but it is surrounded by an envelope of hot material that was likely ejected from the pre-supernova system.

    Although this star is a reasonable contender for N103B’s surviving companion, its status cannot be confirmed yet without further investigation and a spectroscopic confirmation. The search is still ongoing.

    Notes

    [1] A white dwarf is the small, dense core of a medium-mass star that is left behind after it has reached the end of its main-sequence lifetime and blown off its outer layers. Our own Sun is expected to become a white dwarf in around five billion years.

    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 10:54 am on March 22, 2017 Permalink | Reply
    Tags: , , , , , , Supernovae   

    From Ethan Siegel: “What Will Happen When Betelgeuse Explodes?” 

    Ethan Siegel
    Mar 22, 2017

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    The constellation of Orion, along with the great molecular cloud complex and including its brightest stars. Betelgeuse, the nearby, bright red supergiant (and supernova candidate), is at the lower left. Rogelio Bernal Andreo

    Every star will someday run out of fuel in its core, bringing an end to its run as natural source of nuclear fusion in the Universe. While stars like our Sun will fuse hydrogen into helium and then — swelling into a red giant — helium into carbon, there are other, more massive stars which can achieve hot enough temperatures to further fuse carbon into even heavier elements. Under those intense conditions, the star will swell into a red supergiant, destined for an eventual supernova after around 100,000 years or so. And the brightest red supergiant in our entire night sky? That’s Betelgeuse, which could go supernova at any time.

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    The color-magnitude diagram of notable stars. The brightest red supergiant, Betelgeuse, is shown at the upper right. European Southern Observatory.

    Honestly, at its distance of 640 light years from us, it could have gone supernova at any time from the 14th century onwards, and we still wouldn’t know. Betelgeuse is one of the ten brightest stars in the sky in visible light, but only 13% of its energy output is detectable to human eyes. If we could see the entire electromagnetic spectrum — including into the infrared — Betelgeuse would, from our perspective, outshine every other star in the Universe except our Sun.

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    Three of the major stars in Orion — Betelgeuse, Meissa and Bellatrix — as revealed in the infrared. In IR light, Betelgeuse (lower left) is the brightest star in the night sky. NASA / WISE.

    It was the first star ever to be resolved as more than a point source. At 900 times the size of our Sun, it would engulf Mercury, Venus, Earth, Mars and even the asteroid belt if it were to replace our parent star. It’s a pulsating star, so its diameter changes with time.

    In addition, it’s constantly losing mass, as the intense fusion reactions begin to expel the outermost, tenuously-held layers. Direct radio observations can actually detect this blown-off matter, and have found that it extends to beyond the equivalent of Neptune’s orbit.

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    The nebula of expelled matter created around Betelgeuse, which, for scale, is shown in the interior red circle. This structure, resembling flames emanating from the star, forms because the behemoth is shedding its material into space. ESO/P. Kervella

    But when we study the night sky, we’re studying the past. We know that Betelgeuse, with an uncertain mass between about 12 and 20 times that of our Sun, was never destined to live very long: maybe around 10 million years only. The more massive a star is, the faster it burns through its fuel, and Betelgeuse is burning so very, very brightly: at around 100,000 times the luminosity of our Sun. It’s currently in the final stages of its life — as a red supergiant — meaning that when the innermost core begins fusing silicon and sulphur into iron, nickel and cobalt, the star itself will only have minutes left.

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    The anatomy of a very massive star throughout its life, culminating in a Type II Supernova. Nicole Rager Fuller for the NSF.

    At those final moments, the core will be incredibly hot, yet iron, nickel and cobalt will be unable to fuse into anything heavier. It’s energetically unfavorable to do so, and so no new radiation will be produced in the innermost regions. Yet gravitation is still at play, trying to pull the star’s core in on itself. Without nuclear fusion to hold it up, the core has no other options, and begins to implode. The contraction causes it to heat up, become denser, and achieve pressures like it’s never seen before. And once a critical junction has passed, it happens: the atomic nuclei in the star’s core begin a runaway fusion reaction all at once.

    This is what creates a Type II supernova: the core-collapse of an ultra-massive star. After a brief, initial flash, Betelgeuse will brighten tremendously over a period of weeks, rising to a maximum brightness that, intrinsically, will be billions of times as bright as the Sun. It will remain at maximum brightness for months, as radioactive cobalt and expanding gases cause a continuous bright emission of light.

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    At peak brightness, a supernova can shine nearly as brightly as the rest of the stars in a galaxy combined. This 1994 image shows a typical example of a core-collapse supernova relative to its host galaxy. NASA/ESA, The Hubble Key Project Team and The High-Z Supernova Search Team

    Supernovae have occurred in our Milky Way in the past: in 1604, 1572, 1054 and 1006, among others, with a number of them being so bright that they were visible during the day. But none of them were as close at Betelgeuse.

    At only 600-or-so light years distant, Betelgeuse will be far closer than any supernova ever recorded by humanity. It’s fortunately still far away enough that it poses no danger to us. Our planet’s magnetic field will easily deflect any energetic particles that happen to come our way, and it’s distant enough that the high-energy radiation reaching us will be so low-density that it will have less of an impact on you than the banana you had at breakfast. But oh, will it ever appear bright.

    Not only will Betelgeuse be visible during the day, but it will rival the Moon for the second-brightest object in the sky. Some models “only” have Betelgeuse getting as bright as a thick crescent moon, while others will see it rival the entire full moon. It will conceivably be the brightest object in the night sky for more than a year, until it finally fades away to a dimmer state.

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    The ultra-massive star Wolf-Rayet 124, shown with its surrounding nebula, is one of thousands of Milky Way stars that could be our galaxy’s next supernova. Betelgeuse is merely the closest known potential candidate. Hubble Legacy Archive / A. Moffat / Judy Schmidy

    Unfortunately, the key question of “when” is not one we have an answer to; thousands of other stars in the Milky Way may go supernova before Betelgeuse does. Until we develop an ultra-powerful neutrino telescope to measure the energy spectrum of neutrinos being generated by (and hence, which elements are being fused inside) a star like Betelgeuse, hundreds of light years away, we won’t know how close it is to going supernova. It could have exploded already, with the light from the cataclysm already on its way towards us… or it could remain no different than it appears today for another hundred thousand years.

    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 3:07 pm on March 15, 2017 Permalink | Reply
    Tags: ASCR Discovery, Coding a Starkiller, DOE, , Supernovae   

    From OLCF via ASCR and DOE: “Coding a Starkiller” 

    i1

    Oak Ridge National Laboratory

    OLCF

    ASCR

    March 2017

    The Titan supercomputer and a tool called Starkiller help Stony Brook University-led team simulate key moments in exploding stars.

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    A volume rendering of the density after 0.6 and 0.9 solar mass white dwarfs merge. The image is derived from a calculation performed on the Oak Ridge Leadership Computing facility’s Titan supercomputer. The model used Castro, an adaptive mesh astrophysical radiation hydrodynamics simulation code. Image courtesy of Stony Brook University / Max Katz et al.

    The spectacular Supernova 1987A, whose light reached Earth on Feb. 23 of the year it’s named for, captured the public’s fancy. It’s located at the edge of the Milky Way, in a dwarf galaxy called the Large Magellanic Cloud. It had been four centuries since earthlings had witnessed light from a star exploding in our galaxy.

    1
    NASA

    A supernova’s awesome light show heralds a giant star’s death, and the next supernova’s post-mortem will generate reams of data, compared to the paltry dozen or so neutrinos and X-rays harvested from the 1987 event.

    Astrophysicists Michael Zingale and Bronson Messer aren’t waiting. They’re aggressively anticipating the next supernova by leading teams in high-performance computer simulations of explosive stellar events, including different supernova types and their accompanying X-ray bursts. Zingale, of Stony Brook University, and Messer, of the Department of Energy’s Oak Ridge National Laboratory (ORNL), are in the midst of an award from the DOE Office of Science’s Innovative and Novel Computational Impact on Theory and Experiment (INCITE) program. It provides an allocation of 45 million processor hours of computer time on Titan, a Cray XK7 that’s one of the world’s most powerful supercomputers, at the Oak Ridge Leadership Computing Facility, or OLCF – a DOE Office of Science user facility.

    The simulations run on workhorse codes developed by the INCITE collaborators and at the DOE’s Lawrence Berkeley National Laboratory – codes that “are often modified toward specific problems,” Zingale says. “And the common problem we share with ORNL is that we have to put more and more of our algorithms on the Titan graphics processor units (GPUs),” specialized computer chips that accelerate calculations. While the phenomena they’re modeling “are really far away and on scales that are hard to imagine,” the codes have other applications closer to home: “terrestrial phenomena, like terrestrial combustion.” The team’s codes – Maestro, Castro, Chimera and FLASH – are available to other modelers free through online code repository Github.

    With a previous INCITE award, the researchers realized the possibility of attacking the GPU problem together. They envisioned codes comprised of multiphysics modules that compute common pieces of most kinds of explosive activities, Messer says. They dubbed the growing collection of GPU-enabled modules Starkiller.

    “Starkiller ties this INCITE project together,” he says. “We realized we didn’t want to reinvent the wheel with each new simulation.” For example, a module that tracks nuclear burning helps the researchers create larger networks for nucleosynthesis, a supernova process in which elements form in the turbulent flow on the stellar surface.

    “In the past, we were able to do only a little more than a dozen different elements, and now we’re routinely doing 150,” Messer says. “We can make the GPU run so much faster. That’s part of Titan’s advantage to us.”

    Supernova 1987A, a type II supernova, arose from the gravitational collapse of a stellar core, the consistent fate of massive stars. Type Ia supernovae follow from intense thermonuclear activities that eventually drive the explosion of a white dwarf – a star that has used up all its hydrogen. Zingale’s group is focused on type Ia, Messer’s on type II. A type II leaves a remnant star; a type Ia does not.

    Stars like the sun burn hydrogen into helium and, over enormous stretches of time, burn the helium into carbon. Once our sun starts burning carbon, it will gradually peter out, Messer says, because it’s not massive enough to turn the carbon into something heavier.

    “A star begins life as a big ball of hydrogen, and its whole life is this fight between gravity trying to suck it into the middle and thermonuclear reactions keeping it supported against its own gravity,” he adds. “Once it gets to the point where it’s burning some carbon, the sun will just give up. It will blow a big smoke ring into space and become a planetary nebula, and at the center it will become a white dwarf.”

    Zingale is modeling two distinct thermonuclear modes. One is for a white dwarf in a binary system – two stars orbiting one another – that consumes additional material from its partner. As the white dwarf grows in mass, it gets hotter and denser in the center, creating conditions that drive thermonuclear reactions.

    “This star is made mostly of carbon and oxygen,” Zingale says. “When you get up to a few hundred million K, you have densities of a few billion grams per cubic centimeter. Carbon nuclei get fused and make things like neon and sodium and magnesium, and the star gets energy out in that process. We are modeling the star’s convection, the creation of a rippling burning front that converts the carbon and oxygen into heavier elements such as iron and nickel. This creates such an enormous amount of energy that it overcomes the force of gravity that’s holding the star together, and the whole thing blows apart.”

    The other mode is being modeled with former Stony Brook graduate student and INCITE co-principal investigator Max Katz, who want to understand whether merging stars can create a burning point that leads to a supernova, as some observations suggest. His simulations feature two white dwarfs so close that they emit gravitational radiation, robbing energy from the system and causing the stars to spiral inward. Eventually, they get so close that the more massive one rips the lesser apart via tidal energy.

    Zingale’s group also continues to model the convective burning on stars, known as X-ray bursts, providing a springboard to more in-depth studies. He says they’re the first to simulate them in three dimensions. That work and additional supernova studies were supported by the DOE Office of Science and performed at OLCF and the National Energy Research Scientific Computing Center, a DOE Office of Science user facility at Lawrence Berkeley National Laboratory.

    See the full article here .

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    ORNL is managed by UT-Battelle for the Department of Energy’s Office of Science. DOE’s Office of Science is the single largest supporter of basic research in the physical sciences in the United States, and is working to address some of the most pressing challenges of our time.

    i2

    The Oak Ridge Leadership Computing Facility (OLCF) was established at Oak Ridge National Laboratory in 2004 with the mission of accelerating scientific discovery and engineering progress by providing outstanding computing and data management resources to high-priority research and development projects.

    ORNL’s supercomputing program has grown from humble beginnings to deliver some of the most powerful systems in the world. On the way, it has helped researchers deliver practical breakthroughs and new scientific knowledge in climate, materials, nuclear science, and a wide range of other disciplines.

    The OLCF delivered on that original promise in 2008, when its Cray XT “Jaguar” system ran the first scientific applications to exceed 1,000 trillion calculations a second (1 petaflop). Since then, the OLCF has continued to expand the limits of computing power, unveiling Titan in 2013, which is capable of 27 petaflops.


    ORNL Cray XK7 Titan Supercomputer

    Titan is one of the first hybrid architecture systems—a combination of graphics processing units (GPUs), and the more conventional central processing units (CPUs) that have served as number crunchers in computers for decades. The parallel structure of GPUs makes them uniquely suited to process an enormous number of simple computations quickly, while CPUs are capable of tackling more sophisticated computational algorithms. The complimentary combination of CPUs and GPUs allow Titan to reach its peak performance.

    The OLCF gives the world’s most advanced computational researchers an opportunity to tackle problems that would be unthinkable on other systems. The facility welcomes investigators from universities, government agencies, and industry who are prepared to perform breakthrough research in climate, materials, alternative energy sources and energy storage, chemistry, nuclear physics, astrophysics, quantum mechanics, and the gamut of scientific inquiry. Because it is a unique resource, the OLCF focuses on the most ambitious research projects—projects that provide important new knowledge or enable important new technologies.

     
  • richardmitnick 2:23 pm on March 15, 2017 Permalink | Reply
    Tags: , , , , , Supernovae   

    From Astronomy: “There’s a supernova occurring right now in NGC 5643” 

    Astronomy magazine

    astronomy.com

    March 15, 2017
    Alison Klesman

    Meet “Bob,” the second Type Ia supernova in the galaxy since 2013

    1
    Racheal Beaton / Carnegie Institution for Science

    When most people hear the word supernova, they envision a massive star reaching the end of its life and exploding outwards to leave a ghostly remnant in its place. This is called a Type II supernova — the spectacular Supernova 1987A, which recently celebrated its 30th anniversary, was a Type II.

    2
    Supernova 1987A NASA

    Alternatively, a Type Ia supernova occurs when a white dwarf, the remnant of a Sun-like star, grows too massive after stripping a binary companion star of its outer layers. When the white dwarf reaches a critical mass, a runaway fusion reaction occurs in its core and the star explodes in a Type Ia supernova. Such a supernova has just been spotted occurring in a galaxy about 55 million light-years away.

    Announced by Rachael Beaton at the the Observatories of the Carnegie Institution for Science in Pasadena, CA, and known as 2017cbv (though Beaton has nicknamed it Bob), the explosion was spotted in NGC 5643, a spiral galaxy in the constellation Lupus. The area of the sky it inhabits is also part of the area covered by the Carnegie-Irvine Galaxy Survey, a project aimed at gathering optical and near-infrared images of bright Southern Hemisphere galaxies. NGC 5643 was also the home galaxy of SN 2013aa, which occurred in early 2013.

    Type Ia supernovae play an extremely important role as rungs on the astronomical distance ladder that allows astronomers to measure the distance to faraway galaxies. They’ve also played a critical role in measuring the accelerating expansion of the universe. Because they occur in white dwarfs of exactly the same mass every time (that critical mass mentioned earlier: about 1.4 times the mass of the Sun), Type Ia supernovae are always the same brightness, which means astronomers can use them as standard candles. Knowing how bright the explosion is in terms of absolute luminosity allows astronomers to then work backwards to calculate the distance to the object based on how bright it appears.

    But the word “exactly” is perhaps a bit misleading. Not every star system in which a Type Ia supernova occurs can be exactly the same. Moreover, events in the real world do not always reflect the precise nature of theoretical calculations — as in, some white dwarfs might explode at a mass slightly under 1.4 solar masses, while others might grow a little heavier than this limit before exploding. The fact that 2017cbv is the second recorded Type Ia supernova to occur in NGC 5643 is thus extremely valuable. By comparing the distance to the galaxy as calculated from each supernova, astronomers can better characterize the real-world variance in supernova Type Ia magnitudes that occur, which in turn will improve the accuracy of using these events to measure distance.

    See the full article here .

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  • richardmitnick 11:37 am on March 14, 2017 Permalink | Reply
    Tags: , , , , Supernovae,   

    From Weizmann: “Explosive Material: The Making of a Supernova” 

    Weizmann Institute of Science logo

    Weizmann Institute of Science

    Pre-supernova stars may show signs of instability for months before the big explosion

    14.03.2017

    In the most common type of supernova, the iron core of a massive star suddenly collapses in on itself and the outer layers are thrown out into space in a spectacular explosion. New research led by Weizmann Institute of Science researchers shows that the stars that become so-called core-collapse supernovae might already exhibit instability for several months before the big event, spewing material into space and creating a dense gas shell around themselves. They think that many massive stars, including the red super-giants that are the most common progenitors of these supernovae, may begin the process this way.

    This insight into the conditions leading up to core collapse arose from a unique collaboration called the Palomar Transient Factory, a fully automated sky survey using the telescopes of the Palomar observatory in southern California.


    Palomar Transient Factory, located in San Diego County, California

    Astrophysicists halfway around the globe, in Israel, are on call for the telescope, which scans the California night sky for the sudden appearance of new astronomical “transients” that were not visible before – which can indicate new supernovae. In October, 2013, Dr. Ofer Yaron, in the Weizmann Institute’s Particle Physics and Astrophysics Department, got the message that a potential supernova had been sighted, and he immediately alerted Dr. Dan Perley who was observing that night with the Keck telescope in Hawaii, and NASA’s Swift Satellite.


    Keck Observatory, Mauna Kea, Hawaii, USA


    NASA/SWIFT Telescope

    At Keck, the researchers soon began to record the spectra of the event. Because they had started observing only three hours into the blast, the picture the team managed to assemble was the most detailed ever of the core collapse process. “We had x-rays, ultraviolet, four spectroscopic measurements from between six and ten hours post-explosion to work with,” says Yaron.

    In the most common type of supernova, the iron core of a massive star suddenly collapses in on itself and the outer layers are thrown out into space in a spectacular explosion. New research led by Weizmann Institute of Science researchers shows that the stars that become so-called core-collapse supernovae might already exhibit instability for several months before the big event, spewing material into space and creating a dense gas shell around themselves. They think that many massive stars, including the red super-giants that are the most common progenitors of these supernovae, may begin the process this way.

    This insight into the conditions leading up to core collapse arose from a unique collaboration called the Palomar Transient Factory, a fully automated sky survey using the telescopes of the Palomar observatory in southern California. Astrophysicists halfway around the globe, in Israel, are on call for the telescope, which scans the California night sky for the sudden appearance of new astronomical “transients” that were not visible before – which can indicate new supernovae. In October, 2013, Dr. Ofer Yaron, in the Weizmann Institute’s Particle Physics and Astrophysics Department, got the message that a potential supernova had been sighted, and he immediately alerted Dr. Dan Perley who was observing that night with the Keck telescope in Hawaii, and NASA’s Swift Satellite. At Keck, the researchers soon began to record the spectra of the event. Because they had started observing only three hours into the blast, the picture the team managed to assemble was the most detailed ever of the core collapse process. “We had x-rays, ultraviolet, four spectroscopic measurements from between six and ten hours post-explosion to work with,” says Yaron.

    In a study recently published in Nature Physics, Yaron, Weizmann Institute researchers Profs. Avishay Gal-Yam and Eran Ofek, and their teams, together with researchers from the California Institute of Technology and other institutes in the United States, Denmark, Sweden, Ireland, Israel and the UK, analyzed the unique dataset they had collected from the very first days of the supernova.

    The time window was crucial: It enabled the team to detect material that had surrounded the star pre- explosion, as it heated up and became ionized and was eventually overtaken by the expanding cloud of stellar matter. Comparing the observed early spectra and light-curve data with existing models, accompanied by later radio observations, led the researchers to conclude that the explosion was preceded by a period of instability lasting for around a year. This instability caused material to be expelled from the surface layers of the star, forming the circumstellar shell of gas that was observed in the data. Because this was found to be a relatively standard type II supernova, the researchers believe that the instability they revealed may be a regular warm up act to the immanent explosion.

    “We still don’t really understand the process by which a star explodes as a supernova,” says Yaron, “These findings are raising new questions, for example, about the final trigger that tips the star from merely unstable to explosive. With our globe-spanning collaboration that enables us to alert various telescopes to train their sights on the event, we are getting closer and closer to understanding what happens in that instant, how massive stars end their life and what leads up to the final explosion.”

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    Prof. Avishay Gal-Yam’s research is supported by the Benoziyo Endowment Fund for the Advancement of Science; the Yeda-Sela Center for Basic Research; the Deloro Institute for Advanced Research in Space and Optics; and Paul and Tina Gardner. Prof. Gal-Yam is the recipient of the Helen and Martin Kimmel Award for Innovative Investigation.

    Dr. Eran Ofek’s research is supported by the Helen Kimmel Center for Planetary Science; Paul and Tina Gardner, Austin, TX; Ilan Gluzman, Secaucus, NJ; and the estate of Raymond Lapon.

    See the full article here .

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    Weizmann Institute Campus

    The Weizmann Institute of Science is one of the world’s leading multidisciplinary research institutions. Hundreds of scientists, laboratory technicians and research students working on its lushly landscaped campus embark daily on fascinating journeys into the unknown, seeking to improve our understanding of nature and our place within it.

    Guiding these scientists is the spirit of inquiry so characteristic of the human race. It is this spirit that propelled humans upward along the evolutionary ladder, helping them reach their utmost heights. It prompted humankind to pursue agriculture, learn to build lodgings, invent writing, harness electricity to power emerging technologies, observe distant galaxies, design drugs to combat various diseases, develop new materials and decipher the genetic code embedded in all the plants and animals on Earth.

    The quest to maintain this increasing momentum compels Weizmann Institute scientists to seek out places that have not yet been reached by the human mind. What awaits us in these places? No one has the answer to this question. But one thing is certain – the journey fired by curiosity will lead onward to a better future.

     
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