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  • richardmitnick 10:55 am on January 2, 2019 Permalink | Reply
    Tags: , , , Cassiopeia A supernova remnant, Center for Computation and Visualization at Brown University, , , Harvard-Smithsonian Center for Astrophysics (CfA), Stepping inside a dead star, VR-virtual-reality   

    From Harvard Gazette: “Stepping inside a dead star” 

    Harvard University
    Harvard University


    From Harvard Gazette

    December 21, 2018
    Juan Siliezar

    Team uses detailed data to create a virtual-reality display of what’s left after explosion.

    Cassiopeia A, the youngest known supernova remnant in the Milky Way, is the remains of a star that exploded almost 400 years ago. The star was approximately 15 to 20 times the mass of our sun and sat in the Cassiopeia constellation, almost 11,000 light-years from earth.

    Though stunningly distant, it’s now possible to step inside a virtual-reality (VR) depiction of what followed that explosion.

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    Wearing VR goggles Kim Arcand views a 3-D representation of the Cassiopeia A supernova remnant, pictured above, at the YURT VR Cave at Brown.

    A team led by Kimberly Kowal Arcand from the Harvard-Smithsonian Center for Astrophysics (CfA) and the Center for Computation and Visualization at Brown University has made it possible for astronomers, astrophysicists, space enthusiasts, and the simply curious to experience what it’s like inside a dead star. Their efforts are described in a recent paper in Communicating Astronomy with the Public.

    The VR project — believed to be the first of its kind, using X-ray data from NASA’s Chandra X-ray Observatory mission (which is headquartered at CfA), infrared data from the Spitzer Space Telescope, and optical data from other telescopes — adds new layers of understanding to one of the most famous and widely studied objects in the sky.

    NASA/Chandra X-ray Telescope

    NASA/Spitzer Infrared Telescope

    “Our universe is dynamic and 3-D, but we don’t get that when we are constantly looking at things” in two dimensions, said Arcand, the visualization lead at CfA.

    The project builds on previous research done on Cas A, as it’s commonly known, that first rendered the dead star into a 3-D model using the X-ray and optical data from multiple telescopes.

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    Cassiopeia A

    Arcand and her team used that data to convert the model into a VR experience by using MinVR and VTK, two data visualization platforms. The coding work was primarily handled by Brown computer science senior Elaine Jiang, a co-author on the paper.

    The VR experience lets users walk inside a colorful digital rendering of the stellar explosion and engage with parts of it while reading short captions identifying the materials they see.

    “Astronomers have long studied supernova remnants to better understand exactly how stars produce and disseminate many of the elements observed on Earth and in the cosmos at large,” Arcand said.

    When stars explode, they expel all of their elements into the universe. In essence, they help create the elements of life, from the iron in our blood to the calcium in our bones. All of that, researchers believe, comes from previous generations of exploded stars.

    In the 3-D model of Cas A, and now in the VR model, elements such as iron, silicon, and sulfur are represented by different colors. Seeing it in 3-D throws Cas A into fresh perspective, even for longtime researchers and astronomers who build models of supernova explosions.

    “The first time I ever walked inside the same data set that I have been staring at for 20 years, I just immediately was fascinated by things I had never noticed, like how various bits of the iron were in different locations,” Arcand said. “The ability to look at something in three dimensions and being immersed in it just kind of opened up my eyes to think about it in different ways.”

    The VR platforms also opens understanding of the supernova remnant, which is the strongest radio source beyond our solar system, to new audiences. VR versions of Cas A are available by request for a VR cave (a specially made room in which the floors and walls are projection screens), as well as on Oculus Rift, a VR computer platform. As part of this project, the team also created a version that works with Google Cardboard or similar smartphone platforms. In a separate but related project, Arcand and a team from CfA worked with the Smithsonian Learning Lab to create a browser-based, interactive, 3-D application and 360-degree video of Cas A that works with Google Cardboard and similar platforms.

    “My whole career has been looking at data and how we take data and make it accessible or visualize it in a way that adds meaning to it that’s still scientific,” Arcand said.

    VR is an almost perfect avenue for this approach, since it has been surging in popularity as both entertainment and an educational tool. It has been used to help medical staff prepare for surgeries, for example, and video game companies have used it to add excitement and immersion to popular games.

    Arcand hopes to make Cas A accessible to even more people, such as the visually impaired, by adding sound elements to the colors in the model.

    Reaction to the VR experience has been overwhelmingly positive, Arcand said. Experts and non-experts alike are hit by what Arcand calls “awe moments” of being inside and learning about something so massive and far away.

    “Who doesn’t want to walk inside a dead star?” Arcand said.

    See the full article here .

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    Harvard University campus
    Harvard University is the oldest institution of higher education in the United States, established in 1636 by vote of the Great and General Court of the Massachusetts Bay Colony. It was named after the College’s first benefactor, the young minister John Harvard of Charlestown, who upon his death in 1638 left his library and half his estate to the institution. A statue of John Harvard stands today in front of University Hall in Harvard Yard, and is perhaps the University’s best known landmark.

    Harvard University has 12 degree-granting Schools in addition to the Radcliffe Institute for Advanced Study. The University has grown from nine students with a single master to an enrollment of more than 20,000 degree candidates including undergraduate, graduate, and professional students. There are more than 360,000 living alumni in the U.S. and over 190 other countries.

     
  • richardmitnick 4:17 pm on December 12, 2017 Permalink | Reply
    Tags: , , , Cassiopeia A supernova remnant, , , Oxygen is the most abundant element in the human body (about 65% by mass),   

    From Chandra: “Chandra Reveals the Elementary Nature of Cassiopeia A” 

    NASA Chandra Banner

    NASA Chandra Telescope

    NASA Chandra

    2017-12-12

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    Cassiopeia A

    Where do most of the elements essential for life on Earth come from? The answer: inside the furnaces of stars and the explosions that mark the end of some stars’ lives.

    Astronomers have long studied exploded stars and their remains — known as “supernova remnants” — to better understand exactly how stars produce and then disseminate many of the elements observed on Earth, and in the cosmos at large.

    Due to its unique evolutionary status, Cassiopeia A (Cas A) is one of the most intensely studied of these supernova remnants. A new image from NASA’s Chandra X-ray Observatory shows the location of different elements in the remains of the explosion: silicon (red), sulfur (yellow), calcium (green) and iron (purple). Each of these elements produces X-rays within narrow energy ranges, allowing maps of their location to be created. The blast wave from the explosion is seen as the blue outer ring.

    X-ray telescopes such as Chandra are important to study supernova remnants and the elements they produce because these events generate extremely high temperatures — millions of degrees — even thousands of years after the explosion. This means that many supernova remnants, including Cas A, glow most strongly at X-ray wavelengths that are undetectable with other types of telescopes.

    Chandra’s sharp X-ray vision allows astronomers to gather detailed information about the elements that objects like Cas A produce. For example, they are not only able to identify many of the elements that are present, but how much of each are being expelled into interstellar space.

    The Chandra data indicate that the supernova that produced Cas A has churned out prodigious amounts of key cosmic ingredients. Cas A has dispersed about 10,000 Earth masses worth of sulfur alone, and about 20,000 Earth masses of silicon. The iron in Cas A has the mass of about 70,000 times that of the Earth, and astronomers detect a whopping one million Earth masses worth of oxygen being ejected into space from Cas A, equivalent to about three times the mass of the Sun. (Even though oxygen is the most abundant element in Cas A, its X-ray emission is spread across a wide range of energies and cannot be isolated in this image, unlike with the other elements that are shown.)

    Astronomers have found other elements in Cas A in addition to the ones shown in this new Chandra image. Carbon, nitrogen, phosphorus and hydrogen have also been detected using various telescopes that observe different parts of the electromagnetic spectrum. Combined with the detection of oxygen, this means all of the elements needed to make DNA, the molecule that carries genetic information, are found in Cas A.

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    Periodic Table of Elements. Credit: NASA/CXC/K. Divona

    Oxygen is the most abundant element in the human body (about 65% by mass), calcium helps form and maintain healthy bones and teeth, and iron is a vital part of red blood cells that carry oxygen through the body. All of the oxygen in the Solar System comes from exploding massive stars. About half of the calcium and about 40% of the iron also come from these explosions, with the balance of these elements being supplied by explosions of smaller mass, white dwarf stars.

    While the exact date is not confirmed , many experts think that the stellar explosion that created Cas A occurred around the year 1680 in Earth’s timeframe. Astronomers estimate that the doomed star was about five times the mass of the Sun just before it exploded. The star is estimated to have started its life with a mass about 16 times that of the Sun, and lost roughly two-thirds of this mass in a vigorous wind blowing off the star several hundred thousand years before the explosion.

    Earlier in its lifetime, the star began fusing hydrogen and helium in its core into heavier elements through the process known as “nucleosynthesis.” The energy made by the fusion of heavier and heavier elements balanced the star against the force of gravity. These reactions continued until they formed iron in the core of the star. At this point, further nucleosynthesis would consume rather than produce energy, so gravity then caused the star to implode and form a dense stellar core known as a neutron star.

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    Pre-Supernova Star: As it nears the end of its evolution, heavy elements produced by nuclear fusion inside the star are concentrated toward the center of the star. Illustration Credit: NASA/CXC/S. Lee

    The exact means by which a massive explosion is produced after the implosion is complicated, and a subject of intense study, but eventually the infalling material outside the neutron star was transformed by further nuclear reactions as it was expelled outward by the supernova explosion.

    Chandra has repeatedly observed Cas A since the telescope was launched into space in 1999. The different datasets have revealed new information about the neutron star in Cas A, the details of the explosion, and specifics of how the debris is ejected into space.

    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 3:33 pm on June 27, 2017 Permalink | Reply
    Tags: , , , Cassiopeia A supernova remnant, , MPA, , ,   

    From Max Planck Institute for Astrophysics, Garching: “Neutrinos as drivers of supernovae” 

    Max Planck Institute for Astrophysics, Garching

    June 26, 2017
    Dr. Hans-Thomas Janka
    Max Planck Institute for Astrophysics, Garching
    Phone:+49 89 30000-2228
    Fax:+49 89 30000-2235
    thj@mpa-garching.mpg.de

    Dr. Hannelore Hämmerle
    Max Planck Institute for Astrophysics, Garching
    Phone:+49 89 30000-3980
    hhaemmerle@mpa-garching.mpg.de

    1
    Time evolution of the radioactive 56Ni in the ejecta of a 3D simulation of a neutrino-driven supernova explosion. The images show the non-spherical distribution from shortly after the onset of the explosion (3.25 seconds) until a late time (6236 seconds) when the final asymmetry is determined. The colours represent radial velocities according to the scales given for each panel. © MPA

    Radioactive elements in gaseous supernova remnant Cassiopeia A provide glimpses into the explosion of massive stars.

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    Cassiopeia A. NASA/CXC/SAO

    NASA/Chandra Telescope

    Stars exploding as supernovae are the main sources of heavy chemical elements in the Universe. In these star explosions, radioactive atomic nuclei are synthesized in the hot, innermost regions during the explosion and can thus provide insights into the unobservable physical processes that initiate the blast. Using elaborate computer simulations, a team of researchers from the Max Planck Institute for Astrophysics (MPA) and the research institute RIKEN in Japan were able to explain the recently measured spatial distributions of radioactive titanium and nickel in Cassiopeia A, a roughly 340 year old gaseous remnant of a nearby supernova.

    RIKEN campus

    The computer models yield strong support for the theoretical idea that such stellar death events can be initiated and powered by neutrinos escaping from the neutron star left behind at the origin of the explosion.

    Massive stars end their lives in gigantic explosions, so-called supernovae. Within millions of years of stable evolution, these stars have built up a central core composed of mostly iron. When the core reaches about 1.5 times the mass of the Sun, it collapses under the influence of its own gravity and forms a neutron star. Enormous amounts of energy are released in this catastrophic event, mostly by the emission of neutrinos. These nearly massless elementary particles are abundantly produced in the interior of the new-born neutron star, where the density is higher than in atomic nuclei and the temperature can reach 500 billion degrees Kelvin.

    The physical processes that trigger and drive the explosion have been an unsolved puzzle for more than 50 years. One of the theoretical mechanisms proposed invokes the neutrinos, because they carry away more than hundred times the energy needed for a typical supernova. Leaking out from the hot interior of the neutron star, a small fraction of the neutrinos are absorbed in the surrounding gas. This heating causes violent motions of the gas, similar to those in a pot of boiling water on a stove. When the bubbling of the gas becomes sufficiently powerful, the supernova explosion sets in as if the lid of the pot were blown off. The outer layers of the dying star are expelled into circumstellar space, and with them all the chemical elements that the star has assembled by nuclear burning during its life. But also new elements are created in the hot ejecta of the explosion, among them radioactive species such as 44Ti (titanium with 22 protons and 22 neutrons in its atomic nuclei) and 56Ni (28/28 neutrons/protons), which decay to stable calcium and iron, respectively. The thus released radioactive energy makes a supernova shine bright for years.

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    Observed distribution of 44Ti (blue) and iron (white, red) in Cassiopeia A. The visible iron is mostly the radioactive decay product of 56Ni. The yellow cross marks the geometrical centre of the explosion, the white cross and the arrow indicate the current location and the direction of motion of the neutron star. © Macmillan Publishers Ltd: Nature; from Grefenstette et al., Nature 506, 339 (2014); Fe distribution courtesy of U.~Hwang.)

    Because of the wild boiling of the neutrino-heated gas, the blast wave starts out non-spherically and imprints a large-scale asymmetry on the ejected stellar matter and the supernova as a whole, in agreement with the observation of clumpiness and asymmetries in many supernovae and their gaseous remnants. The initial asymmetry of the explosion has two immediate consequences. On the one hand, the neutron star receives a recoil momentum opposite to the direction of the stronger explosion, where the supernova gas is expelled with more violence. This effect is similar to the kick a rowing boat receives when a passenger jumps off. On the other hand, the production of heavy elements from silicon to iron, in particular also of 44Ti and 56Ni, is more efficient in directions where the explosion is stronger and where more matter is heated to high temperatures. “We have predicted both effects some years ago by our three-dimensional (3D) simulations of neutrino-driven supernova explosions”, says Annop Wongwathanarat, researcher at RIKEN and lead author of the corresponding publication of 2013, at which time he worked at MPA in collaboration with his co-authors H.-Thomas Janka and Ewald Müller. “The asymmetry of the radioactive ejecta is more pronounced the larger the neutron star kick is”, he adds. Since the radioactive atomic nuclei are synthesized in the innermost regions of the supernova, in the very close vicinity of the neutron star, their spatial distribution reflects explosion asymmetries most directly.

    New observations of Cassiopeia A (Cas A), the gaseous remnant of a supernova whose light reached the Earth around the year 1680, could meanwhile confirm this theoretical prediction. Because of its young age and relative proximity at a distance of just 11,000 light years, Cas A offers two great advantages for the measurements. First, the radioactive decay of 44Ti is still an efficient energy source, and the presence of this atomic nucleus can therefore be mapped in 3D with high precision in the whole remnant by detecting the high-energy X-ray radiation from the radioactive decays. Second, also the velocity of the neutron star is known with its magnitude and its direction on the plane of the sky.

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    Observable radioactive nickel (56Ni, green) and titanium (44Ti, blue) as predicted by the 3D simulation of a neutrino-driven supernova explosion shown in Fig. 1. The orientation is optimized for closest possible similarity to the Cas A image of Fig. 2a. The neutron star is marked by a white cross and shifted away from the centre of the explosion (red plus symbol) because of its kick velocity. The neutron star motion points away from the hemisphere that contains most of the ejected 44Ti. Iron of its kick velocity. The neutron star motion points away from the hemisphere that contains most of the ejected 44Ti. Iron (the decay product of Ni56) can be observed only in an outer, hot shell of Cas A. © MPA

    Since the neutron star propagates with an estimated speed of at least 350 kilometres per second, the asymmetry in the spatial distribution of the radioactive elements is expected to be very pronounced. Exactly this is seen in the observations . While the compact remnant speeds toward the lower hemisphere, the biggest and brightest clumps with most of the 44Ti are found in the upper half of the gas remnant. The computer simulation, viewed from a suitably chosen direction, exhibits a striking similarity to the observational image. But not only the spatial distributions of titanium and iron resemble those in Cas A (for a 3D visualization, see Fig. 3 in comparison with the 3D imaging of Cas A available at the weblink http://3d.si.edu/explorer?modelid=45). Also the total amounts of these elements, their expansion velocities, and the velocity of the neutron star are in amazing agreement with those of Cas A. “This ability to reproduce basic properties of the observations impressively confirms that Cas A may be the remnant of a neutrino-driven supernova with its violent gas motions around the nascent neutron star”, concludes H.-Thomas Janka.

    But more work is needed to finally prove that the explosions of massive stars are powered by energy input from neutrinos. “Cas A is an object of so much interest and importance that we must also understand the spatial distributions of other chemical species such as silicon, argon, neon, and oxygen”, remarks Ewald Müller, pointing to the beautiful multi-component morphology of Cas A revealed by 3D imaging (see http://3d.si.edu/explorer?modelid=45). One example is also not enough for making a fully convincing case. Therefore the team has joined a bigger collaboration to test the theoretical predictions for neutrino-driven explosions by a close analysis of a larger sample of young supernova remnants. Step by step the researchers thus hope to collect evidence that is able to settle the long-standing problem of the supernova mechanism.

    See the full article here .

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