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  • richardmitnick 2:22 pm on May 12, 2018 Permalink | Reply
    Tags: , , , Betelgeuse, , , , ,   

    From Harvard-Smithsonian Center for Astrophysics via EarthSky: “What’s a safe distance between us and a supernova?” 

    Harvard Smithsonian Center for Astrophysics


    From Harvard-Smithsonian Center for Astrophysics

    EarthSky

    May 11, 2018

    And how many potentially exploding stars are located within the unsafe distance?

    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 light-years as the closest safe distance between Earth and a supernova.

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    Image of remnant of SN 1987A as seen at optical wavelengths with the Hubble Space Telescope in 2011.

    NASA/ESA Hubble Telescope

    This supernova was the closest in centuries, and it was visible to the eye alone. It was located on the outskirts of the Tarantula Nebula in the Large Magellanic Cloud, a satellite galaxy to our Milky Way. It was located approximately 168,000 light-years from Earth. Image via NASA, ESA, and P. Challis (Harvard-Smithsonian Center for Astrophysics).

    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 would 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.

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    Relative dimensions of IK Pegasi A (left), IK Pegasi B (lower center) and our sun (right). The smallest star here is the nearest known supernova progenitor candidate, at 150 light-years away. Image via RJHall on Wikimedia Commons.

    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.

    RIGEL-BETELGEUSE-ANTARES Digital image ©Michael Carroll

    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, that is), 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 knows. 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.

    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 the few million years 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.

    See the full article here .

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    The Center for Astrophysics combines the resources and research facilities of the Harvard College Observatory and the Smithsonian Astrophysical Observatory under a single director to pursue studies of those basic physical processes that determine the nature and evolution of the universe. The Smithsonian Astrophysical Observatory (SAO) is a bureau of the Smithsonian Institution, founded in 1890. The Harvard College Observatory (HCO), founded in 1839, is a research institution of the Faculty of Arts and Sciences, Harvard University, and provides facilities and substantial other support for teaching activities of the Department of Astronomy.

     
  • richardmitnick 9:25 pm on April 20, 2018 Permalink | Reply
    Tags: , , , , Betelgeuse, Capturing Neutrinos from a Star’s Final Hours,   

    From AAS NOVA: “Capturing Neutrinos from a Star’s Final Hours” Revised for Betelgeuse 

    AASNOVA

    AAS NOVA

    20 April 2018
    Kerry Hensley

    Betelgeuse, in the infrared from the Herschel Space Observatory, is a superluminous red giant star 650 light-years away. Stars much more massive, like Betelgeuse, end their lives as supernova ESA/Herschel/PACS/L. Decin et al

    Stars much more massive than the Sun, like Betelgeuse, end their lives as supernovae — releasing neutrinos detectable by sensitive observatories on Earth. [ESA/Herschel/PACS/L. Decin et al.]

    What happens on the last day of a massive star’s life? In the hours before the star collapses and explodes as a supernova, the rapid evolution of material in its core creates swarms of neutrinos. Observing these neutrinos may help us understand the final stages of a massive star’s life — but they’ve never been detected.

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    A view of some of the 1,520 phototubes within the MiniBooNE neutrino detector. Observations from this and other detectors are helping to illuminate the nature of the mysterious neutrino. [Fred Ullrich/FNAL]

    Silent Signposts of Stellar Evolution

    The nuclear fusion that powers stars generates tremendous amounts of energy. Much of this energy is emitted as photons, but a curious and elusive particle — the neutrino — carries away most of the energy in the late stages of stellar evolution.

    Stellar neutrinos can be created through two processes: thermal processes and beta processes. Thermal processes — e.g., pair production, in which a particle/antiparticle pair are created — depend on the temperature and pressure of the stellar core. Beta processes — i.e., when a proton converts to a neutron, or vice versa — are instead linked to the isotopic makeup of the star’s core. This means that, if we can observe them, beta-process neutrinos may be able to tell us about the last steps of stellar nucleosynthesis in a dying star.

    But observing these neutrinos is not so easily done. Neutrinos are nearly massless, neutral particles that interact only feebly with matter; out of the whopping ~1060 neutrinos released in a supernova explosion, even the most sensitive detectors only record the passage of just a few. Do we have a chance of detecting the beta-process neutrinos that are released in the final few hours of a star’s life, before the collapse?

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    Neutrino luminosities leading up to core collapse. Shortly before collapse, the luminosity of beta-process neutrinos outshines that of any other neutrino flavor or origin. [Adapted from Patton et al. 2017]

    Modeling Stellar Cores

    To answer this question, Kelly Patton (University of Washington) and collaborators first used a stellar evolution model to explore neutrino production in massive stars. They modeled the evolution of two massive stars — 15 and 30 times the mass of our Sun — from the onset of nuclear fusion to the moment of collapse.

    The authors found that in the last few hours before collapse, during which the material in the stars’ cores is rapidly upcycled into heavier elements, the flux from beta-process neutrinos rivals that of thermal neutrinos and even exceeds it at high energies. So now we know there are many beta-process neutrinos — but can we spot them?

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    Neutrino and antineutrino fluxes at Earth from the last 2 hours of a 30-solar-mass star’s life compared to the flux from background sources. The rows represent calculations using two different neutrino mass hierarchies. Click to enlarge. [Patton et al. 2017]

    Observing Elusive Neutrinos

    For an imminent supernova at a distance of 1 kiloparsec, the authors find that the presupernova electron neutrino flux rises above the background noise from the Sun, nuclear reactors, and radioactive decay within the Earth in the final two hours before collapse.

    Based on these calculations, current and future neutrino observatories should be able to detect tens of neutrinos from a supernova within 1 kiloparsec, about 30% of which would be beta-process neutrinos. As the distance to the star increases, the time and energy window within which neutrinos can be observed gradually narrows, until it closes for stars at a distance of about 30 kiloparsecs.

    Are there any nearby supergiants soon to go supernova so these predictions can be tested? At a distance of only 650 light-years, the red supergiant star Betelgeuse should produce detectable neutrinos when it explodes — an exciting opportunity for astronomers in the far future!

    Citation

    Kelly M. Patton et al 2017 ApJ 851 6. http://iopscience.iop.org/article/10.3847/1538-4357/aa95c4/meta

    Related journal articles
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    See the full article for further references with links.

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    AAS Mission and Vision Statement

    The mission of the American Astronomical Society is to enhance and share humanity’s scientific understanding of the Universe.

    The Society, through its publications, disseminates and archives the results of astronomical research. The Society also communicates and explains our understanding of the universe to the public.
    The Society facilitates and strengthens the interactions among members through professional meetings and other means. The Society supports member divisions representing specialized research and astronomical interests.
    The Society represents the goals of its community of members to the nation and the world. The Society also works with other scientific and educational societies to promote the advancement of science.
    The Society, through its members, trains, mentors and supports the next generation of astronomers. The Society supports and promotes increased participation of historically underrepresented groups in astronomy.
    The Society assists its members to develop their skills in the fields of education and public outreach at all levels. The Society promotes broad interest in astronomy, which enhances science literacy and leads many to careers in science and engineering.

    Adopted June 7, 2009

     
  • richardmitnick 8:53 am on February 11, 2018 Permalink | Reply
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    From EarthSky: “Somber Betelgeuse in Orion’s shoulder” 

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    EarthSky

    February 11, 2018

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    Tonight, look for ruddy-hued Betelgeuse, one of the sky’s most famous stars. Kids especially like Betelgeuse, because its name sounds so much like beetle juice. The movie by that same name perpetuated this pronunciation.

    But astronomers pronounce it differently. We say BET-el-jews.

    People have described this star as somber or sometimes even grandfatherly. That may be because of Betelgeuse’s ruddy complexion, which, as a matter of fact, indicates that this star is well into the autumn of its years.

    Betelgeuse is no ordinary red star. It’s a magnificently rare red supergiant. According to Professor Jim Kaler – whose website Stars you should check out – there might be only one red supergiant star like Betelgeuse for every million or so stars in our Milky Way galaxy.

    At this time of year, Betelgeuse’s constellation – Orion the Hunter – ascends to its highest point in the heavens around 8 to 9 p.m. local time – that’s the time on your clock no matter where you are on the globe – with the Hunter symbolically reaching the height of his powers.

    As night passes – with Earth turning eastward under the stars – Orion has his inevitable fall, shifting lower in the sky by late evening.

    Orion slowly heads westward throughout the late evening hours and plunges beneath the western horizon in the wee hours after midnight.

    Orion Nebula ESO/VLT

    Bottom line: The ruddy star Betelgeuse depicts Orion’s shoulder. In mid-February, Orion reaches his high point for the night around 8 to 9 p.m. local time.

    See the full article here .

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    Deborah Byrd created the EarthSky radio series in 1991 and founded EarthSky.org in 1994. Today, she serves as Editor-in-Chief of this website. She has won a galaxy of awards from the broadcasting and science communities, including having an asteroid named 3505 Byrd in her honor. A science communicator and educator since 1976, Byrd believes in science as a force for good in the world and a vital tool for the 21st century. “Being an EarthSky editor is like hosting a big global party for cool nature-lovers,” she says.

     
  • richardmitnick 10:54 am on March 22, 2017 Permalink | Reply
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    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 9:40 pm on December 19, 2016 Permalink | Reply
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    From U Texas Austin via Pys.org: “Famous red star Betelgeuse is spinning faster than expected; may have swallowed a companion 100,000 years ago” 

    THIS POST IS DEDICATED TO J.L.T. who knew how to get it done.

    U Texas Austin bloc

    University of Texas at Austin

    phys.org

    phys.org

    December 19, 2016
    No writer credit

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    This 2012 infrared image of Betelgeuse by the orbiting Herschel telescope shows two shells of interacting matter on one side of the star. Credit: L. Decin/University of Leuven/ESA

    Astronomer J. Craig Wheeler of The University of Texas at Austin thinks that Betelgeuse, the bright red star marking the shoulder of Orion, the hunter, may have had a past that is more interesting than meets the eye. Working with an international group of undergraduate students, Wheeler has found evidence that the red supergiant star may have been born with a companion star, and later swallowed that star. The research is published today in the journal Monthly Notices of the Royal Astronomical Society.

    For such a well-known star, Betelgeuse is mysterious. Astronomers know that it’s a red supergiant, a massive star that is nearing the end of its life and so has bloated up to many times its original size. Someday it will explode as a supernova, but no one knows when.

    “It might be ten thousand years from now, or it might be tomorrow night,” Wheeler, a supernova expert, said.

    A new clue to the future of Betelgeuse involves its rotation. When a star inflates to become a supergiant, its rotation should slow down. “It’s like the classic spinning ice skater—not bringing her arms in, but opening her arms up,” Wheeler said. As the skater opens her arms, she slows down. So, too, should Betelgeuse’s rotation have slowed as the star expanded. But that is not what Wheeler’s team found.

    “We cannot account for the rotation of Betelgeuse,” Wheeler said. “It’s spinning 150 times faster than any plausible single star just rotating and doing its thing.”

    He directed a team of undergraduates including Sarafina Nance, Manuel Diaz, and James Sullivan of The University of Texas at Austin, as well as visiting students from China and Greece, to study Betelgeuse with a computer modeling program called MESA. The students used MESA to model Betelgeuse’s rotation for the first time.

    Wheeler said in contemplating the star’s puzzlingly fast rotation, he began to speculate. “Suppose Betelgeuse had a companion when it was first born? And let’s just suppose it is orbiting around Betelgeuse at an orbit about the size that Betelgeuse is now. And then Betelgeuse turns into a red supergiant and absorbs it—swallows it.”

    He explained that the companion star, once swallowed, would transfer the angular momentum of its orbit around Betelgeuse to that star’s outer envelope, speeding Betelgeuse’s rotation.

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    This view of Orion, the hunter, was captured from McDonald Observatory on November 20, 2016 by a DSLR camera piggybacked on a three-inch telescope for a 12-minute exposure. Supergiant star Betelgeuse forms the hunter’s bright orange shoulder at top left. Credit: Tom Montemayor

    Wheeler estimates that the companion star would have had about the same mass as the Sun, in order to account for Betelgeuse’s current spin rate of 15 km/sec.

    While an interesting idea, is there any evidence for this swallowed-companion theory? In a word: perhaps.

    If Betelgeuse did swallow a companion star, it’s likely that the interaction between the two would cause the supergiant to shoot some matter out into space, Wheeler said.

    Knowing how fast matter comes off of a red giant star, about 10 km/sec, Wheeler said he was able to roughly estimate how far from Betelgeuse this matter should be today.

    “And then I went to the literature, in my naiveté, and read about Betelgeuse, and it turns out there’s a shell of matter sitting beyond Betelgeuse only a little closer than what I had guessed,” Wheeler said.

    Infrared images taken of Betelgeuse in 2012 by Leen Decin of the University of Leuven in Belgium with the orbiting Herschel telescope show two shells of interacting matter on one side of Betelgeuse. Various interpretations exist; some say that this matter is a bow shock created as Betelgeuse’s atmosphere pushes through the interstellar medium as it races through the galaxy.

    No one knows the origin with certainty. But “the fact is,” Wheeler said, “there is evidence that Betelgeuse had some kind of commotion on roughly this timescale”—that is, 100,000 years ago when the star expanded into a red supergiant.

    The swallowed companion theory could explain both Betelgeuse’s rapid rotation and this nearby matter.

    Wheeler and his team of students are continuing their investigations into this enigmatic star. Next, he says, they hope to probe Betelgeuse using a technique called “asteroseismology”—looking for sound waves impacting the surface of the star, to get clues to what’s happening deep inside its obscuring cocoon. They will also use the MESA code to better understand what would happen if Betelgeuse ate a companion star.

    See the full article here .

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    In 1839, the Congress of the Republic of Texas ordered that a site be set aside to meet the state’s higher education needs. After a series of delays over the next several decades, the state legislature reinvigorated the project in 1876, calling for the establishment of a “university of the first class.” Austin was selected as the site for the new university in 1881, and construction began on the original Main Building in November 1882. Less than one year later, on Sept. 15, 1883, The University of Texas at Austin opened with one building, eight professors, one proctor, and 221 students — and a mission to change the world. Today, UT Austin is a world-renowned higher education, research, and public service institution serving more than 51,000 students annually through 18 top-ranked colleges and schools.

     
  • richardmitnick 9:18 am on December 8, 2016 Permalink | Reply
    Tags: , , Betelgeuse, , , Rigel   

    From EarthSky: “Focus on stars Betelgeuse and Rigel” 

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    EarthSky

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    Photo of the constellation Orion by Flickr user jpstanley

    Tonight … look for Orion the Hunter, one of the easiest constellations to identify in the night sky. Many constellations have a single bright star, but the majestic constellation Orion can boast of two: Rigel and Betelgeuse. You can’t miss these two brilliant beauties if you look eastward around 7:30 to 8:30 p.m. (your local time). Rigel and Betelgeuse reside on opposite sides of Orion’s Belt – three medium-bright stars in a short, straight row.

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    Rigel http://www.solarsystemquick.com/universe/rigel-star.htm

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    Betelgeuse https://encrypted-tbn1.gstatic.com/images?q=tbn:ANd9GcTUC2HlLVdPrM6Ps_y2l_c9NqCgs8p7OFkyliDEy3JIyEZbscLw

    The star Rigel depicts Orion’s left foot. A blue-white supergiant and one of the most luminous stars known, it’s nearly 800 light-years away. If Rigel were as close as Sirius, the brightest star visible to the eye (and only about 8.6 light-years away), Rigel would shine much more brilliantly than Venus, our sky’s brightest planet.

    Betelgeuse – the other bright star in Orion – represents the Hunter’s right shoulder. A red supergiant, Betelgeuse is no slouch of a star either. In fact, if Betelgeuse replaced the sun in our solar system, its outer layers would extend past Earth and Mars and to nearly the orbit of Jupiter.

    On a dark night, when the moon has dropped out of the evening sky in the second half of December 2016, you might want to look at the magnificent Orion Nebula, or M42, the fuzzy patch in Orion’s Sword.

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    Orion Nebula. NASA/ESA Hubble

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    Image Credit: scalleja

    Bottom line: Many constellations have a bright star, but Orion has two: Rigel and Betelgeuse. You’ll also easily recognize Orion by its “Belt” stars, three medium-bright stars in a short, straight row.

    See the full article here .

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  • richardmitnick 7:56 am on October 9, 2015 Permalink | Reply
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    From Daily Galaxy- “Image of the Day: Is the Milky Way’s Red Giant Betelgeuse the Next Nearby Supernova? 

    Daily Galaxy
    The Daily Galaxy

    October 08, 2015
    No Writer Credit

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    While there is, on average, only one supernova per galaxy per century, there is something on the order of 100 billion galaxies in the observable Universe. Taking 10 billion years for the age of the Universe (it’s actually 13.7 billion, but stars didn’t form for the first few hundred million), Dr. Richard Mushotzky of the NASA Goddard Space Flight Center, derived a figure of 1 billion supernovae per year, or 30 supernovae per second in the observable Universe! Could the Milky Way’s red giant star, Betelgeuse be the next?

    Betelgeuse, one of the brightest stars in the sky, could burst into its supernova phase and become as bright as a full moon — and last for as long as a year.

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    The pink arrow at the star on left labeled α indicates Betelgeuse in Orion.

    The massive star, visible in the winter sky over most of the world as a bright, reddish star, could explode as a supernova anytime within the next 100,000 years.

    Most astronomers today believe that one of the plausible reasons we have yet to detect intelligent life in the universe is due to the deadly effects of local supernova explosions that wipe out all life in a given region of a galaxy.

    The red giant Betelgeuse, once so large it would reach out to Jupiter’s orbit if placed in our own solar system, has shrunk by 15 percent over the past decade in a half, although it’s just as bright as it’s ever been.

    Betelgeuse, whose name derives from Arabic, is easily visible in the constellation Orion. It gave Michael Keaton’s character his name in the movie Beetlejuice and was the home system of Galactic President Zaphod Beeblebrox in The Hitchhiker’s Guide to the Galaxy.

    Red giant stars are thought to have short, complicated and violent lifespans. Lasting at most a few million years, they quickly burn out their hydrogen fuel and then switch to helium, carbon and other elements in a series of partial collapses, refuelings and restarts.

    Betelgeuse, which is thought to be reaching the end of its lifespan, may be experiencing one of those collapses as it switches from one element to another as nuclear-fusion fuel.

    “We do not know why the star is shrinking,” said Townes’ Berkeley colleague Edward Wishnow. “Considering all that we know about galaxies and the distant Universe, there are still lots of things we don’t know about stars, including what happens as red giants near the ends of their lives.”

    If Betelgeuse goes nova, it could offer Earth’s astronomers an up close look at how supernovae evolve and the physics that governs how they work. The problem is that it is not clear when that will happen. While stories have been circulating that the star could explode in 2012, the odds of that are actually quite small. Betelgeuse may explode tomorrow night, or it may not go nova until the year 100,000 A.D. It’s impossible to know.

    Betelgeuse is beyond the death beam distance — somewhere within 30 light years range — where it could do ultimate damage to Earth. The explosion won’t do the Earth any harm, as a star has to be relatively close — on the order of 25 light years — to do that. Betelgeuse is about 600 light years distant.

    Betelgeuse, one of the most luminous stars known and ten times the size of the Sun, is thought to be only 10 million years old. The more massive a star is the shorter its lifespan, which is why astronomers think it has an outside chance of exploding relatively soon.

    Late in 2009, astronomers witnessed the largest explosion ever recorded: a super giant star two hundred times bigger than the sun utterly obliterated by runaway thermonuclear reactions triggered by gamma ray-driven antimatter production. The resulting blast was visible for months because it unleashed a cloud of radioactive material over fifty times the size of our own star, giving off a nuclear fission glow visible from galaxies away.

    The super-supernova SN2007bi is an example of a pair-instability breakdown, and that’s like calling an atomic bomb a “plutonium-pressing” device. At sizes of around four megayottagrams (that’s thirty-two zeros) giant stars are supported against gravitational collapse by gamma ray pressure. The hotter the core, the higher the energy of these gamma rays — but if they get too energetic, these gamma rays can begin pair production: creating an electron-positron matter-antimatter pair out of pure energy as they pass an atom. Yes, this does mean that the entire stellar core acts as a gigantic particle accelerator.

    The antimatter annihilates with its opposite, as antimatter is wont to do, but the problem is that the speed of antimatter explosion — which is pretty damn fast — is still a critical delay in the gamma-pressure holding up the star. The outer layers sag in, compressing the core more, raising the temperature, making more energetic gamma rays even more likely to make antimatter, and suddenly the whole star is a runaway nuclear reactor beyond the scale of the imagination. The entire thermonuclear core detonates at once, an atomic warhead that’s not just bigger than the Sun — it’s bigger than the Sun plus the mass of another ten close-by stars.

    The entire star explodes. No neutron star, no black hole, nothing left behind but an expanding cloud of newly radioactive material and empty space where once was the most massive item you can actually have without ripping space. The explosion alone triggers alchemy on a suprasolar scale, converting stars’ worth of matter into new radioactive elements.

    Certain rare stars –real killers, type 11 stars — are core-collapse hypernova that generate deadly gamma ray bursts (GRBs). These long burst objects release 1000 times the non-neutrino energy release of an ordinary core-collapse supernova. Concrete proof of the core-collapse GRB model came in 2003.

    It was made possible in part to a fortuitously “nearby” burst whose location was distributed to astronomers by the Gamma-ray Burst Coordinates Network (GCN). On March 29, 2003, a burst went off close enough that the follow-up observations were decisive in solving the gamma-ray burst mystery. The optical spectrum of the afterglow was nearly identical to that of supernova SN1998bw. In addition, observations from x-ray satellites showed the same characteristic signature of “shocked” and “heated” oxygen that’s also present in supernovae. Thus, astronomers were able to determine the “afterglow” light of a relatively close gamma-ray burst (located “just” 2 billion light years away) resembled a supernova.

    It isn’t known if every hypernova is associated with a GRB. However, astronomers estimate only about one out of 100,000 supernovae produce a hypernova. This works out to about one gamma-ray burst per day, which is in fact what is observed.

    What is almost certain is that the core of the star involved in a given hypernova is massive enough to collapse into a black hole (rather than a neutron star). So every GRB detected is also the “birth cry” of a new black hole.

    Scientists agree that new observations of T Pyxidis in the constellation Pyxis (the compass) using the International Ultraviolet Explorer satellite, indicate the white dwarf is part of a close binary system with a sun, and the pair are 3,260 light-years from Earth and much closer than the previous estimate of 6,000 light-years.

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    T Pyxidis
    Hubble telescope picture of T Pyxidis, from a compilation of data taken on Feb. 26, 1994, and June 16, Oct. 7, and Nov. 10, 1995, by the Wide Field and Planetary Camera 2 [WFPC2].

    NASA Hubble Telescope
    NASA/ESA Hubble

    NASA Hubble WFPC2
    NASA Hubble WFPC2

    The white dwarf in the T Pyxidis system is a recurrent nova, which means it undergoes nova (thermonuclear) eruptions around every 20 years. The most recent known events were in 1967, 1944, 1920, 1902, and 1890. These explosions are nova rather than supernova events, and do not destroy the star, and have no effect on Earth. The astronomers do not know why the there has been a longer than usual interval since the last nova eruption.

    Astronomers believe the nova explosions are the result of an increase of mass as the dwarf siphons off hydrogen-rich gases from its stellar companion. When the mass reaches a certain limit a nova is triggered. It is unknown whether there is a net gain or loss of mass during the siphoning/explosion cycle, but if the mass does build up the so-called Chandrasekhar Limit could be reached, and the dwarf would then become a Type 1a supernova.

    In this event the dwarf would collapse and detonate a massive explosion resulting in its total destruction. This type of supernova releases 10 million times the energy of a nova.

    Observations of the white dwarf during the nova eruptions suggest its mass is increasing, and pictures from the Hubble telescope of shells of material expelled during the previous explosions support the view. Models estimate the white dwarf’s mass could reach the Chandrasekhar Limit in around 10 million years or less.

    According to the scientists the supernova would result in gamma radiation with an energy equivalent to 1,000 solar flares simultaneously — enough to threaten Earth by production of nitrous oxides that would damage and perhaps destroy the ozone layer. The supernova would be as bright as all the other stars in the Milky Way put together. One of the astronomers, Dr. Edward Sion, from Villanova University, said the supernova could occur “soon” on the timescales familiar to astronomers and geologists, but this is a long time in the future, in human terms.

    Astronomers think supernova explosions closer than 100 light years from Earth would be catastrophic, but the effects of events further away are unclear and would depend on how powerful the supernova is. The research team postulate it could be close enough and powerful enough to damage Earth, possibly severely, although other researchers, such as Alex Filippenko at UC Berkeley, who specializes in supernovae, active galaxies, black holes, gamma-ray bursts, and the expansion of the universe, disagree with the calculations and believe the supernova, if it occurred, would be unlikely to damage the planet.

    See the full article here .

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  • richardmitnick 8:35 am on July 18, 2014 Permalink | Reply
    Tags: , , , Betelgeuse, ,   

    From SPACE.com: “Betelgeuse: The Eventual Supernova” 

    SpacedotcomHeader

    SPACE.com

    July 18, 2013
    Elizabeth Howell

    Betelgeuse is a star nearing the end of its life. Because it is creating heavier and heavier elements in its core that could be used for stars after it dies, a NASA story once dubbed the red giant a workaholic.

    bet
    Betelgeuse in comparison

    The star is a famous one among amateur astronomers not only for its size and brightness, but also because it is part of Orion, a bright winter constellation in the Northern Hemisphere.

    orion
    Orion constellation

    Professional astronomers also keep a close eye on the star, as it is notoriously variable: its diameter changes from anywhere between 550 to 920 times the sun’s diameter. In 2013, astronomers said Betelgeuse is likely to crash into a “cosmic wall” of interstellar dust in a few thousand years.

    Locating Betelgeuse

    Ancient astronomers would have easily spotted Betelgeuse because of its size and relatively close distance from Earth: it is about 600 light-years away and has a variable brightness generally peaking at 0.4 and falling below 1.2. Some 20th-century observations by the American Association of Variable Star Observers suggested peak magnitudes of 0.2 in 1933 and 1942. It is the 12th brightest star in the night sky. [The Brightest Stars in the Sky: A Starry Countdown]

    The star’s location is:

    Right ascension: 05 hours 55 minutes 10.3 seconds
    Declination: +07 degrees 24 minutes 25 seconds

    It is probable that the name “Betelgeuse” originated in Arabic words, but the star had other names (for example) in Sanskrit, traditional Chinese and even in Hawaiian; in the latter, it was known as Kauluakoko.

    The coming supernova

    When astronomers say Betelgeuse is expected to explode soon, they mean shortly in astronomical terms: within a million years, according to several sources. Predicting exactly when it will turn into a supernova is difficult, however, as it depends on precise calculations of its mass as well as an understanding of what is going on inside the star.

    Betelgeuse is so vast — its size would extend beyond Jupiter’s orbit if it were placed in the sun’s position in the solar system — that several telescopes have captured images of the star and spotted it shedding mass. Starting in 1993 and continuing for at least 15 years, its radius shrank by 15 percent, an astonishing amount for so short a time.

    “We do not know why the star is shrinking,” said Edward Wishnow, a research physicist at UC Berkeley’s Space Sciences Laboratory, in 2009.

    “Considering all that we know about galaxies and the distant universe, there are still lots of things we don’t know about stars, including what happens as red giants near the ends of their lives.”

    Nearing the wall

    As the star prepares for what could be a large explosion, another challenge awaits: it is expected to crash into a wall of interstellar dust in the next few thousand years.

    An infrared Herschel Space Observatory image released in 2013 suggested it would crash into the dust at a speed of 66,960 miles per hour (107,761 kilometers per hour.)

    ESA Herschel
    ESA/Herschel

    The crash would take a while to complete: the solar wind is expected to touch the line around 5,000 years from now, with the heart of the star crashing into the bar 12,500 years after that.

    See the full article here.


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