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Thread: Our Galaxy's Next Supernova

  1. Default Our Galaxy's Next Supernova

    ""The diversity of the phenomena of nature is so great, and the treasures hidden in the heavens so rich, precisely in order that the human mind shall never be lacking in fresh nourishment." -Johannes Kepler

    So said the man who, in 1604, discovered the supernova that was the last to be seen, visually, within our own galaxy. Although it's likely that two others occurred subsequently, they were not visible to human eyes, and only with powerful telescopes were their remnants discovered.

    But earlier this week, the first supernova of the year was discovered, in a galaxy 25 million light years away, NGC 3239. The supernova, indicated below, is now known as SN 2012a.

    With a typical rate of about one supernova per galaxy per century, one can't help but wonder, as one of our perennial commenters did, what we'd see -- and how quickly we'd manage to see it -- if a supernova went off in our own galaxy.

    Remember, now, there are two ways we can have a supernova, but both ways involve a runaway nuclear fusion reaction, giving off a tremendous amount of light and energy. But most of the energy, perhaps surprisingly, isn't in the form of light! Let's take you inside a star that goes supernova during those critical few seconds.

    Although there are shocks and heat that are produced, you'll see that the interior reactions produce neutrinos, nearly all of which do not interact with the outer layers of the star! A few of them do, as do all of the protons, neutrons and electrons produced, and the overall production isn't instantaneous. But while it takes some time -- a couple of hours -- for the shock to reach the outer surface of the dying star, the neutrinos make it out almost immediately!

    What this means is that when we have a star go supernova, neutrinos get emitted from it before the light does! We actually discovered this, firsthand, back in 1987.

    When supernova 1987a went off just 168,000 light years away, it was close enough -- and we had enough neutrino detectors operating -- that we detected 23 (anti)neutrinos over a timespan of about 13 seconds. The largest detector, Kamiokande-II, contained 3,000 tons of water and detected 11 antineutrinos.

    Today, the detector that sits in the same spot, Super Kamiokande-III, contains 50,000 tons of water and contains over 11,000 photomultiplier tubes. (There are many other excellent neutrino detectors around the world, but I'm focusing on this one in particular as an example.)

    This setup is so amazing because it can not only detect neutrinos, but it can reconstruct the direction, energy, and point-of-interaction of even a single neutrino fortunate enough to interact with any one particle in those 50,000 tons of water!

    Depending on where a potential supernova goes off in our galaxy, we would expect Super Kamiokande-III to see anywhere from a few thousand antineutrinos (for something on the other side of the galaxy) to over ten million of them, all in the timespan of just 10-15 seconds!

    Neutrino detectors from all over the world would see a flood of detections like this, all at the same time, all coming from the same direction. At that point, we'd have something on the order of two-to-three hours to identify the direction of origin of those neutrinos, and point our telescopes towards that direction to try and obtain an optical view of the supernova -- for the very first time -- from its very beginning!

    The closest supernova since 1987 was this one from last year, which we managed to catch just half a day after ignition, which is remarkable.

    We've gotten very close -- mostly by good fortune -- with a very intense hypernova back in 2002.

    Even so, we didn't get to first observe this one, SN 2002ap, until 3-4 hours after first ignition. If the supernova that eventually comes is a type Ia supernova -- which originates from a white dwarf -- we have no way of predicting where in the galaxy that will occur. White dwarfs are simply too abundant, and the locations of almost all of them are simply unknown, and thought to be distributed all over the galaxy.

    But if this originates from a very massive star whose core collapses under its own gravity (i.e., a type II supernova), we have a number of really good candidates, and some outstanding places to look.

    Most obvious is the galactic center, the location of the Milky Way's last known supernova, and also the location of the most massive stars ever discovered within our galaxy. We're certainly going to have many type II supernovae originating here over the next 100,000 years, but we have no way of knowing when we'll see the next one. As you look at the above picture, take a moment to appreciate that it's very likely already happened, and we're just waiting for the neutrinos (and then the light) to get here!

    But there are closer candidates than the galactic center.

    Look inside one of the great, star forming nebulae in our galaxy, and you're going to find some of the hottest, youngest stars you're going to find anywhere in the Universe. This is where the ultra-massive stars live, and in particular, the Eagle Nebula, above, may be home to an extremely recent supernova. The Eagle Nebula, the Orion Nebula, and many other regions filled with new stars are all great places to anticipate the next supernova.

    But what about known, individual stars? While there are many good candidates, we have two in particualr that we can't help but talk about.

    Eta Carinae, in the very last stages of its life, could literally go supernova at any second. But it may also live hundreds, thousands, or even tens of thousands more years before it does so. Still, if we get a flood of antineutrinos originating from anywhere near its position in space, this will be the very first place we point our telescopes!

    But unlike all of these candidates that are many thousands of light-years away, we have one good one that's much closer. In fact, it's the closest supernova candidate we have!

    Say hello to Betelgeuse, a red supergiant just 640 light-years distant. Betelgeuse is so gigantic that it literally is the diameter of Saturn's orbit around the Sun! If Betelgeuse went supernova, our neutrino detectors around the globe would detect -- all told -- somewhere in the vicinity of a hundred million (anti)neutrinos, which is more neutrinos of any type than have ever been detected in the history of the world, combined.

    But unless it's one of these known candidates that goes supernova, how will we tell whether it's a type Ia or a type II supernova?

    We can always wait, I suppose. Supernovae of different types have very distinct light-curves, and how the light dies off after it's reached its peak brightness will tell us what type of supernova we had.

    But if something this exciting happens, I'm not going to have that kind of patience. Luckily, I won't need it, because a supernova within our galaxy would likely be the very first detectable observation for the newest type of astronomy: Gravitational-Wave Astronomy!

    Undisturbed by the presence of, well, anything, gravitational waves from a supernova explosion should pass through the intervening star, any gas, dust, or matter completely undisturbed, arriving at the same time the front end of the (anti)neutrino pulse arrives! The wonderful thing is that -- according to our best simulations of general relativity -- type II (core-collapse) and type Ia (inspiraling white dwarfs) should give vast different signals for gravitational waves!

    If we have a type Ia supernova, we expect to see three separate regions to our signal.

    The inspiral phase should give a periodic pulse that increases in frequency and magnitude as the white dwarfs reach their final stage of their separation. As the ignition occurs, there should be a spike in the signal, followed by a "ringdown" phase as the ripples go away. Very distinctive.

    But if we have a type II supernova, from a super-massive collapsing star, we're only going to see two interesting things.

    Just a huge spike -- where the supernova itself occurs -- just a tenth of a second after the core collapses, followed by a very rapidly dying (within 0.02 seconds) ringdown. And so if we want to know what we saw, all we need to do is extract the telltale signal from gravitational waves!

    And if the galaxy's next supernova were to happen today, this is what we'd see!"


    Hmmmmmmm..... I found this a good read as well as a great review. Click the linc fer pics n' graphs n' such!!!!

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  3. Cool

    Granny says when Uncle Ferd passes gas, dat oughta qualify as cosmic wind...

    Astronomers Measure Record Cosmic Winds Near Small Black Hole
    February 23, 2012 - The U.S. space agency says cosmic winds generated by a disk of cosmic gas spinning around a small-scale type of black hole are the fastest ever recorded near such an object.
    NASA researchers say they clocked wind speeds of 32 million kilometers per hour - about 3 percent of the speed of light - using instruments aboard the orbiting Chandra X-ray Observatory. Such tremendous cosmic wind speeds were previously thought to occur only near the largest black holes in the universe. Black holes are the densest, heaviest objects in the universe. Their powerful gravitational fields create vortexes that pull in gas and debris from millions of kilometers around and capture even light in their grip.

    The largest such objects - known as supermassive black holes - are thought to be at the center of most large galaxies, including our own, the Milky Way. They can be millions, or even billions of times more massive than our sun. But stellar-mass black holes are tiny by comparison, with masses just five to 10 times that of the sun.

    The Earth-orbiting Chandra probe shows that the little stellar-mass black hole powering the record-breaking winds orbits a sun-like star in a binary system 28,000 light years from Earth. NASA says the Chandra measurements and data shed important light on the behavior of smaller black holes, and their effect on nearby matter.

    Gas disks like the one observed in the study are composed of the sub-atomic remains of material captured by the black hole’s powerful gravitational vortex, which spins the particles around at nearly light speeds. The energy generated during this process creates cosmic winds. The new study is published in the current issue of The Astrophysical Journal Letters.

    See also:

    Astronomers Say Galaxy May Be Awash with Homeless Planets
    February 24, 2012 - Astronomers say the Milky Way may be swarming with nomad planets wandering through space instead of orbiting a host star, and that the galaxy may have a greater number of unmoored planets than stars.
    Last year, astronomers detected about a dozen nomad planets wandering about the galaxy, using a technique called gravitational microlensing, in which the light of stars is momentarily refocused, and brightened, by the gravity of passing planets. At that time, scientists estimated there could be two Jupiter-sized nomad planets for every typical star with orbiting planets in the Milky Way. Jupiter, a gas giant, is the largest planet in the solar system. A new analysis by researchers at the Kavli Institute for Particle Astrophysics and Cosmology at Stanford University in California now estimates there could be 100,000 times more homeless planets than stars.

    Louis Strigari, a research scientist at Kavli, led the study that calculated the gravitational pull of the Milky Way galaxy and the amount of cosmic matter, or material, available to form nomad planets. "We imagined that the population of a dozen or so Jupiter-mass wandering or nomadic objects is just the tip of the iceberg relative to what’s really out there in terms of our galaxy," said Strigari. "So, if one makes assumptions about how many there are below the mass below Jupiter, then one can obtain a bound [an estimate] on how many of these actually exist.

    While they might seem to be unlikely candidates for life as we know it, StrIgari says it is possible some of these wandering planets could harbor forms of bacterial life, even if they do not enjoy the heat of a sun. “If the object has a thick enough atmosphere and say there’s tectonic activity or radioactivity going on, on the surface of the planet, the heat could get trapped by the thick atmosphere and could potentially be hospitable to microbial life,” said the research scientist.

    Strigari also says there is a slight chance that two nomad planets could collide, flinging bacterial debris into other solar systems. Astronomers hope to confirm the number of wandering planets in the next decade, when a newer generation of larger, more powerful telescopes - including the space-based Wide-Field Infrared Survey Telescope and the ground-based Large Synoptic Survey Telescope proposed by the U.S. space agency (NASA) - begins operating. An article by Louis Strigari and colleagues on nomadic planets is published in the journal Monthly Notices of the Royal Astronomical Society.

    Last edited by waltky; Feb 24 2012 at 09:08 PM.

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  5. Cool

    Carbon-14 spike mystery may be solved...

    Ancient text may solve cosmic mystery
    June 28`12 (UPI) -- An ancient text about a "red crucifix" seen in British evening skies more than 1,200 years ago could explain a mysterious radiation spike, U.S. scientists say.
    The phenomenon in 774 A.D. may have been a previously unrecognized supernova explosion and could explain a mysterious spike in carbon-14 levels in that year's growth rings in Japanese cedar trees, Nature reported Wednesday. Jonathon Allen, a biochemistry major at the University of California, Santa Cruz, heard about research in Japan that found an odd spike in carbon-14 levels in tree rings, probably caused by a burst of high-energy radiation striking the upper atmosphere and increasing the rate at which carbon-14 is formed. However, the only known causes of such bursts are supernova explosions or gigantic solar flares, and there was no historical record of any such events in the dates indicated by the tree rings.

    Allen, intrigued, went on the Internet. "I just did a quick Google search," he said. "I knew that going that far back, there's very limited written history," he said. "The only things I'd ever seen or heard of were religious texts and 'chronicles' that listed kings and queens, wars and things of that nature." His Internet search led to eighth-century entries in the Anglo-Saxon Chronicle in an online library of historical and legal documents hosted by Yale University, where he found a reference to a "red crucifix" that appeared in the heavens "after sunset." "It made me think it's some sort of stellar event," Allen said.

    Astronomers say they are impressed by Allen's find. "The wording suggests that the object was seen in the western skies shortly after sunset," Geza Gyuk, an astronomer at Chicago's Adler Planetarium, said. "That would mean that it would have moved behind the Sun [where it could not be seen] as Earth orbited the Sun. That, along with the dimness of the 'new star' due to dust would go a long way to explaining why no one else would have seen or recorded the event." Numbers of supernovae now known to astronomers "are simply missing" in the historical record, Gyuk said. "The sky is a large place and the historical record is not very good."

    Read more: http://www.upi.com/Science_News/2012...#ixzz1zDriqbEJ

  6. #4
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    I'll bring up WR 104, an unstable Wolf-Rayet star 8000 light years away that could go boom (or has already gone boom, but we don't know it yet), and produce a gamma ray burst that could wipe out life on earth. It's probably not aligned quite right to focus the beam on earth (it comes out of both poles in a narrow beam), but you never know.


  7. Default

    Quote Originally Posted by mamooth View Post
    I'll bring up WR 104, an unstable Wolf-Rayet star 8000 light years away that could go boom (or has already gone boom, but we don't know it yet), and produce a gamma ray burst that could wipe out life on earth. It's probably not aligned quite right to focus the beam on earth (it comes out of both poles in a narrow beam), but you never know.

    mmm, your optimism is so comforting...

  8. Icon17

    Supernovas are traditionally named after composers...

    Supernova 'Mingus' could shed light on dark energy
    10 January 2013 - Astronomers have spotted the most distant supernova ever seen.
    Nicknamed "Mingus", it was described at the 221st American Astronomical Society meeting in the US. These lightshows of dying stars have been seen since ancient times, but modern astronomers use details of their light to probe the Universe's secrets. Ten billion light-years distant, Mingus will help shed light on so-called dark energy, the force that appears to be speeding up cosmic expansion. Formally called SN SCP-0401, the supernova was something of a chance find in a survey carried out in part by the Supernova Cosmology Project (SCP) using the Hubble space telescope, first undertaken in 2004. But the data were simply not good enough to pin down what was seen. As David Rubin of the University of California, Berkeley, lead author on the study, told the AAS meeting, "for a sense of brightness, this supernova is about as bright as a firefly viewed from 3,000 miles away".

    Further news had to wait until astronauts installed the Wide Field Camera 3 on the Hubble telescope in 2009 and again trained it on the candidate, which had - in an SCP tradition of naming supernovae after composers - already been named after jazz musician Charles Mingus. "Unfortunately, it took the development of Wide Field Camera 3 to bring home what the [2004] measurements meant," Mr Rubin told BBC News. "The sensitivity is a few times better, which makes a huge difference, and we have a much cleaner image." The team went on to confirm that the supernova was in fact a Type 1a - a particular class of exploded star whose light occurs in such a regular way that it is known as a "standard candle".

    'Bit of history'

    What interests astronomers trying to find ever more distant Type 1a supernovae - distant both in space and in time - is the chance to compare them to better-known, more local supernovae. "We were able to watch these changes in brightness and spectral features for an event that lasted just a few weeks almost 10 billion years ago," said Saul Perlmutter, who leads the Supernova Cosmology Project. Prof Perlmutter shared the 2011 Nobel prize in physics for work with Type 1a supernovae that proved our Universe is speeding up in its expansion.

    Elucidating the mysterious force, "dark energy", which has been invoked as the cause of the expansion, will require careful study of supernovae all the way back to the epoch of the earliest stars. "We're seeing two-thirds of the way back to the beginning of the Universe, and we're getting a little bit of history where the physics of what makes a supernova explode have to all work out the same way there as they do near here," he told the meeting. The group's study is published online and will appear in the Astrophysical Journal on 20 January.

    Dark ambitions

  9. Icon17

    In about 5,000 years...

    Betelgeuse Hurdles Toward Massive Collision
    January 23, 2013 : Betelgeuse - the nearest red supergiant to Earth - is about 1,000 times the diameter of our Sun and 100,000 times more bright
    A new photo of the star Betelgeuse reveals dramatic events unfolding a mere 643 light years away from Earth. The photo, which provides the far-infrared view of the star, shows arc-shaped waves of solar wind crashing against the interstellar medium. Those waves, scientists estimate, are moving at 30 kilometers per second. The photo was released January 22 by the European Space Agency’s [ESA] Herschel space observatory.

    The red supergiant star Betelgeuse as seen by the ESA’s Herschel space observatory.

    According to a release by the ESA, the waves appear to be heading toward a collision with “an intriguing dusty wall” [the line to the left of the photo] in about 5,000 years. The wall, according to the agency, is either part of the Galaxy’s magnetic field or the edge of a nearby interstellar cloud.

    Inside the arcs, a roiling cloud of red likely is clumpy debris ejected from the star sometime in the past. While the light show on Betelgeuse certainly is captivating, it’s all coming to an end in the very near future, at least in terms of the cosmic clock. The star is heading toward a spectacular supernova sometime in the next few million years.

    Betelgeuse - the nearest red supergiant to Earth - is about 1,000 times the diameter of our Sun, 100,000 times more bright and can be seen from Earth with the naked eye. The star rides the shoulder of the constellation Orion the Hunter, as an orange-red star above and to the left of Orion’s belt.


  10. Icon3

    Supernova may come from white dwarf...

    Dead stars 'can re-ignite' and explode
    28 August 2014 ~ Astronomers have shown that dead stars known as white dwarfs can re-ignite and explode as supernovas.
    The discovery appears to solve a mystery surrounding the nature of a particular category of stellar explosions known as Type Ia supernovas. Theorists suspected that white dwarfs could explode due to a disruptive interaction with a companion star, but lacked definitive evidence until now. Details of the research appear in the journal Nature. The "smoking gun" in this case was the detection of radioactive nuclei being generated by nuclear fusion in the cosmic blast. Astronomers have long had the tools to detect the signature of this fusion, but had to wait for a supernova to explode nearby in order to begin their observations. Towards the end of its life, a star with the mass of the Sun will shed its outer layers as its core shrinks down to become a white dwarf. Left to their own devices, single white dwarfs will just cool off slowly over time.

    This artist's impression shows a possible mechanism for a Type Ia supernova

    But there is a maximum mass at which a white dwarf can remain stable - a property known as the Chandrasekhar limit, after the Indian-American astrophysicist Subrahmanyan Chandrasekhar. If a white dwarf steals matter from a stellar companion, or collides with another white dwarf, the extra weight can compress the carbon in the star's core until this element undergoes nuclear fusion. The carbon is fused into heavier elements with a sudden release of energy that tears the star apart. Although Type Ia supernovas are expected to occur frequently across the Universe, they are rare occurrences in any one galaxy, with typical rates of one every few hundred years. But an opportunity to observe one of these events came on 21 January 2014, when students at the University College London's teaching observatory at Mill Hill in the UK detected a type Ia supernova, later named SN2014J, in the nearby galaxy M82. Theorists propose that the carbon and oxygen found in a white dwarf should be fused into radioactive nickel during a supernova.

    This nickel should then quickly decay into radioactive cobalt, which would itself subsequently decay, on a somewhat longer timescale, into stable iron. Type Ia supernovas that exploded long ago are the cosmic sources of the iron in the Sun, the Earth and in our blood. This decay chain generates gamma-rays that give rise to bright emission from the location of the supernova. Eugene Churazov and colleagues studied gamma-ray data gathered by the European Space Agency's Integral spacecraft between 50 and 100 days after the explosion. By this time, Dr Churazov explained, "the white dwarf has already expanded to a size larger than our solar system". He told BBC News: "The envelope of ejecta (debris) is semi-transparent, so no matter where the gamma-rays are produced, they are able to escape through the ejecta with a probability on the order of 60-70%."

    Type Ia supernovas are relatively rare occurrences in any one galaxy

    They looked for - and found - the signature of cobalt decay in the profile of gamma-ray emission from the supernova. Moreover, the observed amount of gamma-ray emission was also an excellent match for theoretical models of a white dwarf explosion. However, the researchers were not able to distinguish between the two theoretical scenarios for the initiation of a white dwarf supernova. Dr Churazov explained: "It is perfectly consistent with the simplest scenario, of a single white dwarf with a mass close to the Chandrasekhar limit. But we cannot exclude with this data that this event was caused by a merger [of two white dwarfs]." In a viewpoint piece in the same edition of Nature, Robert P Kirshner, from the Harvard-Smithsonian Center for Astrophysics in Massachusetts, wrote: "Upsetting the conventional wisdom is always a joy in science. You can get prizes for that." But, he explained, "there is also a deep pleasure in showing decisive evidence on an important physical idea that has been used without proof for decades," adding: "It is a wonderful result."


  11. Icon3

    It could be the most powerful supernova ever detected...

    Colossal star explosion detected
    Astronomers have seen what could be the most powerful supernova ever detected. The exploding star was first observed back in June last year but is still radiating vast amounts of energy.
    At its peak, the event was 200 times more powerful than a typical supernova, making it shine with 570 billion times the brightness of our Sun. Researchers think the explosion and ongoing activity have been boosted by a very dense, highly magnetised, remnant object called a magnetar. This object, created as the supernova got going, is probably no bigger than a major city, such as London, and is likely spinning at a fantastic rate - perhaps a thousand times a second. But it probably also is slowing, and as it does so, it is dumping that rotational energy into the expanding shroud of gas and dust thrown off in the explosion.

    Before and after: This event was more than twice as luminous as the previous record-holding supernova

    Prof Christopher Kochanek, from Ohio State University, US, is a member of discovery team. This is how he explains the process of supercharging a supernova: "The idea is that this thing at the centre is very compact. It's probably about the mass of our Sun, and the garbage into which it is dumping its energy is about five to six times the mass of our Sun, and expanding outwards at a rate of, let's say, 10,000km/s. "The trick in getting the supernova to last a long time is to keep dumping energy into this expanding garbage for as long as you can. That's how you get maximum bang for your buck," he told this week's Science In Action programme on the BBC World Service. Details of the event are reported in the latest edition of the journal Science.

    The super-luminous supernova, as it is termed, was spotted some 3.8 billion light-years from Earth by the All Sky Automated Survey for SuperNovae (ASAS-SN). This uses a suite of Nikon long lenses in Cerro Tololo, Chile, to sweep the sky for sudden brightenings. Follow-up observations with larger facilities are then used to investigate targets in more detail. The intention of ASAS-SN is to get better statistics on the different types of supernovas and where they are occurring in the cosmos. Astronomers have long been fascinated by these monster explosions and have come to recognise just how important they are to the story of how the Universe has evolved. Not only do they forge the heavier chemical elements in nature but their shockwaves disturb the space environment, stirring up the gas and dust from which the next generation of stars are formed. The source star for this reported supernova must have been colossal - maybe 50 to 100 times the mass of our Sun.

    Artist's impression: Imagine standing on a planet 10,000 light-years from the supernova

    Such stars begin very voluminous but then shed a lot of mass in great winds that blow out into space. So, by the time this star ended its life, it was very probably greatly reduced in size. "It would have been quite small at the time of death, not tremendously bigger than the Earth," said Prof Kockanek. "It would have been very hot, however: about 100,000 degrees at the surface. Basically, it would have got rid of all of its hydrogen and helium, leaving just the material that had been burnt into carbon and oxygen." There are signs that the supernova may be about to fade, and the team have time on the Hubble space telescope in the coming weeks to try to further understand the mechanisms driving the supernova. "It is an explosion and eventually all explosions have to fade," Prof Kockanek told the BBC. "If it never fades then our interpretation of the event would have to be wrong. On the other hand, if this interpretation is wrong then it's an even more unique object and so in some sense one would be perfectly happy living with that alternative."


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