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  • richardmitnick 9:40 pm on December 19, 2016 Permalink | Reply
    Tags: , , , Betelgeuse,   

    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
    Tags: , , Betelgeuse,   

    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.

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    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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