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Space Science

Astronomers Explode Virtual Supernova 97

Posted by CowboyNeal
from the safest-detonation-yet dept.
DynaSoar writes "Scientists at the University of Chicago's Center for Astrophysical Thermonuclear Flashes have created a simulation of a white dwarf exploding into a type 1a supernova. Using 700 processors and 58,000 hours, they produced a three second movie showing the initial burst that is thought to be the source of much of the iron in the universe. Understanding these supernovas is also important to testing current cosmological theories regarding dark matter and dark energy, as their brightness is used as a measurement of distance, and discrepancies found in the brightness of very distant supernovas consistently seem to indicate a change in the speed of expansion of the universe over time."
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Astronomers Explode Virtual Supernova

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  • by siddesu (698447) on Friday March 23, 2007 @12:35AM (#18454641)
    http://flash.uchicago.edu/website/research/gallery /home.py [uchicago.edu]

    for all alternative OS users out there.
  • Psssh! (Score:5, Funny)

    by PixieDust (971386) on Friday March 23, 2007 @12:38AM (#18454663)
    7000 processors and 58000 hours? SG-1 Did that in a single episode! On a TV special effects budget no less!
  • 58000 hours (Score:4, Interesting)

    by Repton (60818) on Friday March 23, 2007 @12:40AM (#18454671) Homepage
    So, they started the simulation over six years ago?
    • Re: (Score:3, Funny)

      by Anonymous Coward
      Sure it was a coding error that showed up 6 years later...

      Researcher #1: Ooops! It crashed... darn!
      Researcher #2: Crap! After 6 years!...
      Researcher #1: Oh wait.. I have an idea!...
    • Re: (Score:2, Informative)

      by psychrono (1030230)
      I never RTFA, but maybe it was a "cumulative" 58,000 hours across 7,000 processors? That seems a lot more feasible to me... but maybe they did start it over 6 years ago :p
      • Oops... 700 processors, not 7,000. Preview is my friend :)
      • Re: (Score:1, Informative)

        by zapwow (939754)
        If the 58000 hours is not cumulative, then this represents 4.6 millenia of computing time. If that were done with one processor, about 180 supernovae would explode in our galaxy during the computation.
    • Re:58000 hours (Score:5, Informative)

      by Atlantis-Rising (857278) on Friday March 23, 2007 @12:57AM (#18454779) Homepage
      It's probably 58,000 processor hours, which on 700 processors is closer to 83 hours in real time.
    • by mrbluze (1034940)

      So, they started the simulation over six years ago?

      That would still be better than the real thing, which, once viewed, probably happened thousands or millions of years ago!

    • by haisent (696846)
      they just sum up the hours. I think they can frozen the computation at any time by storing all the data in files. so maybe much longer than 6 years.
  • by Var1abl3 (1021413) on Friday March 23, 2007 @12:52AM (#18454757)
    Does anyone else see the "face" that is created during this explosion? I see closed eyes, a nose and even a mouth(all tongue in cheek) ROFLMAO... sorry poor joke..... would love to see this at full speed.
  • Very Subtle (Score:5, Funny)

    by BillGatesLoveChild (1046184) on Friday March 23, 2007 @01:09AM (#18454865) Journal
    > created a simulation of a white dwarf exploding into a type 1a supernova. Using 700 processors and 58,000 hours,

    They probably got Federal Funding for this by explaining it was "like sticking a giant firecracker up a giant frog"
  • The horror! (Score:3, Funny)

    by Tablizer (95088) on Friday March 23, 2007 @01:25AM (#18454943) Homepage Journal
    You insensative clods! They killed my virtual friends and my virtual dog orbiting around that star on a virtual planet! Just because they are bits instead of molecules is no reason to demean them.
  • by Tablizer (95088)
    They literally blew a wod of cash
  • Moo (Score:2, Informative)

    by Chacham (981)
    supernovas

    Shouldn't that be supernovae?
    • by Flying pig (925874) on Friday March 23, 2007 @04:48AM (#18455701)
      "Supernova" is an invented word and the plural is "supernovas". Just like televisions and radios.

      In fact, the word is built out of two Latin adjectives, literally it means an "abovenew". Invented words follow this rule, hence the plural of octopus is octopuses, of satellite is satellites, and of millennium is millenniums. The plural of "vertebra" is "vertebrae" because it is an actual Latin word, not an invented modern one.

      Incidentally, while pursuing this very pedantic note, "satellites" is correct plural but the singular of the original word is "satelles". And the original word is pronounced sat-ell-it-ees. We are a long way from Latin.

      • And then there are words derived from Greek which people think are from Latin. One example is "hippopotamus", whose plural is "hippopotamuses" because it's an English word.

        If anyone ever says "hippopotami", just laugh loudly at them and inform them that the correct quasi-Greek plural is either "hippopotamoi" (spoonfuls-type plural) or "hippoipotamus" (spoonsful-type plural).
      • Um, hi. Astronomer here (not that it matters).

        The word nova in the astronomical context comes from Tycho Brahe, a Danish astronomer who was writing in Latin at the time. The plural is novae, not novas. Although supernova is an English construction, the etymology is derived more directly from this Latin word than other modern inventions. Although both plural forms are strictly correct due to the artificial construction, supernovae is used predominantly in our field.
        • Actually, I know astronomers call them supernovae. Until recently, they also thought Pluto was a planet. Truth is, like a lot of scientists, astronomers create cod Latin and Greek for historical reasons (Latin was the common language of intellectuals, Greek was the language they used when they really didn't want to be overheard...). Unlike Tycho, they don't use either on a regular basis, and they get it wrong. Correct me if I am wrong, but Tycho called them, correctly, "new stars". The nova is an adjective,
        • Re: (Score:3, Informative)

          by dsanfte (443781)
          Both could be correct if you use them properly in the sentence. Supernovae when it's the subject, supernovas when it's the object. Assuming we're treating "supernova" as a regular 1st-declension latin feminine noun.

          Strictly speaking, super (as a preposition of space or location, in this case) takes nova in the ablative case, so the ending on nova is a long a (ahhhhh). If we were writing in Latin I don't know that we'd use the -ae ending for the plural at all. In fact, I'm not sure what the plural would be.
  • by patio11 (857072) on Friday March 23, 2007 @01:35AM (#18454987)
    I'm sorry, I had to check when their acronym spells CATFUC.
  • by icepick72 (834363) on Friday March 23, 2007 @01:39AM (#18455005)
    "they produced a three second movie showing the initial burst that is thought to be the source of much of the iron in the universe"

    Bob: But we'll never get funding with a three second image. This thing had to have caused something useful ..
    Joe: Well, um ... how about something specific like Kevin Federline?
    Bob: No, panders too much to popular culture.
    Joe: That's too bad because my next thought was heavy metal music. Oh, how about some type of boring "metal" like iron ore. It's in some vitamins too which will interest the average consumer.
    Bob: That'll do. We have to get the funding proposal out by noon.

    • by gardyloo (512791)

      Bob: But we'll never get funding with a three second image. This thing had to have caused something useful ..
      Didn't Janet Jackson have a star for that nipple ring thing during the Superbowl kerfluffle? If I remember right, that was 3 seconds or less. If you can get that performance out of a simulation, I guarantee someone, somewhere will give you funding. Then you just have to ask yourself if you want that money ...
  • ...but why do these people persist in blowing so much time and effort and money on stuff like this when there are far more deserving and serious problems to be solved right here and now on good old earth. Hell, we can't even tame hydrogen --> helium let alone oxygen --> iron or whatever it is. Good, solid science for sure, but the priorities seem to be way, way wrong if you ask me.
    • by Tim C (15259)
      There's an old saying, nine women can't have a baby in one month.

      Just because you throw more resources at a problem doesn't necessarily mean that it gets solved any quicker (in many cases, past a certain point it actually gets slower).
    • by Sproggit (18426) on Friday March 23, 2007 @04:07AM (#18455559)
      The priorities are NOT wrong!
      Knowledge for knowledge's sake ALWAYS ends up paying off.

      Just because we dont know how to make our lives better by virtue of gaining this knowledge now, there's no reason to suppose we'll never know (in fact, history indicates that eventually ALL research pays off to some extent).

      If you RTFA and do a slight bit of reasoning (I know, I know, but try), you will see that this research directly helps us understand more of the hydrogen -> helium mechanincs.

      Repeat after me:
      ALL KNOWLEDGE IS VALUABLE.
      KNOWING IS ALWAYS BETTER THAN NOT KNOWING.

      Ignorance being bliss was a concept invented to placate the ignorant.

      • by Nukenbar2 (591848)
        I'm not so sure. I had a roommate in college that always wanted to show me his bowel movements.

        Trust me, that was knowledge that you could live without.

        • by Sproggit (18426)
          Well, if his movements included the remains of undigested previous roomate's bodyparts.... I'd want to know...
    • Re: (Score:3, Funny)

      by Waffle Iron (339739)
      Since you're browsing slashdot when instead you could be working on harnessing fusion power, it would seem that you're just as guilty of having skewed priorities as these astrophysicists.
    • Re: (Score:3, Insightful)

      by timster (32400)
      You got some answers which are good enough, but I'd like to add a point.

      Further development in materials and energy sources today relies upon gaining a better understanding of the physics involved. After all, it's hard to do engineering when you don't know the rules. While we have very good models for large-scale physics, we're still lacking at the subatomic level.

      The difficulty of subatomic physics is that the particles are so small that their influences are difficult to detect. One way to solve that is
    • You're implying that no work is being done taming H-fusion? I think if you compare the funding for fusion research to what astronomers do, you might feel that the ratio is pretty "reasonable".

      Plus, keep in mind that this center gets funding from the DoE. I'm sure you can creatively think of other uses for exploring high-energy thermonuclear reactions in high-resolution detail.
      • OK. I'm happy now. Part of my motivation for the original post was the irritation of seeing projects with real worth being refused funding, and at the same time someone in the Arts being given a buttload of money by the same government so they can work out some new dance steps or whatever.
  • more detail (Score:5, Informative)

    by gsn (989808) on Friday March 23, 2007 @03:07AM (#18455315)
    Gah that article is awful. They link to pretty pictures and blurbs mostly and never really explain what these things are, why they are important or give you any real sense of scale. So since I like to beat on the drum of better communication of science, here is a little more detail to add to the good einhverfr's post.

    The progenitors of SNIa are most likely white dwarfs composed of carbon nitrogen and oxygen, probably with a companion star from which they are stripping matter. They are very compact on the order of a few thousand kilometers at most, and really dense - more than the mass of the sun. They aren't hot enough to support fusion - they are supported by Pauli pressure; quantum mechanics doesn't allow two electrons in the same state at the same time so though gravity tries to compact these objects there is a Pauli pressure outward to balance it.

    This can't go on forever in these progenitor systems however, and if the white dwarf strips enough matter of its companion to get to ~1.4 solar masses (the Chandrashekar limit) then Pauli pressure isn't strong enough to balance gravity and the star begins to collapse and when that happens pressure and temperature rises and somewhere a nuclear fusion flame ignites. Details about what happens near collapse, and where and how the flame ignites, and how many there are and how they progress are still debated. In this particular model they are considering only a single flame (so far) and its a "gravitationally confined detonation" (GCD - the name of this particular model).

    Its a little difficult to get a sense of scale from those videos, though there are numbers in the bottom corner. The flame starts of near or just of center and becomes bubble/mushroom shaped through a Rayleigh-Taylor instability [wikipedia.org] and breaks the stellar surface in under a second. Its less than another second before the ash and flame from the bubble collides at the opposite end of the star. This flame crashing into itself (see video 1) causes compression and a detonation.

    Theres been a lot of debate as to whether its a deflagration or a detonation or whether it transitions from one to the other and how and when that happens and us poor graduate students just hope they don't go crazy over details of the progenitors during our qualifying examinations. This is notable because there appears to be a growing number of voices who are saying that a detonation is necessary. These events are so standard because they all become SNIa if they get near 1.4 solar masses. There is a fair bit of diversity (and some just crazy objects) and most of that probably arises from details during the explosion which is why modeling them is partly why the models are so important.

    There is still a lot of modeling left to do. This flame is producing a lot of heavy elements (there is O, S, Ca, Mg and Si in the early spectra - the silicon feature is around 6150 angstrom in the rest frame and is the marker of a Ia at low to moderate redshifts). As the outer layers expand and become more transparent you see more of the material produced during the explosion and a lot of this is Nickel (Ni-56) which decays to cobalt and powers the light curve so you get this typically 2 week rise and then a slow fall off. Later times most of the Ni has become cobalt which is decaying to iron and you see these elements in the spectrum. The energies we are talking about here are about 10^45 Joules. A H bomb by contrast is 10^15 Joules so 30 order of magnitude. Unless you can picture 10^30 H bombs going off its hard to get a feeling for this number but thats generally the case with numbers in cosmology.

    There are a lot of empirical relations you see from the lightcurve, which are exploited to standardize them (for instance the brighter the supernova, the slower its rate of decline, and there are relations for the colour...) and if a model can replicate them and match the observed lightcurves and spectra then this is a very impressive accomplishment. I skim
    • by andersa (687550)

      Its a little difficult to get a sense of scale from those videos, though there are numbers in the bottom corner. The flame starts of near or just of center and becomes bubble/mushroom shaped through a Rayleigh-Taylor instability and breaks the stellar surface in under a second. Its less than another second before the ash and flame from the bubble collides at the opposite end of the star. This flame crashing into itself (see video 1) causes compression and a detonation.

      I don't get it. The flame expands o

      • It makes sense if you watch the animations after reading that very cogent explaination offered above.
      • Quoth the parent poster:

        I don't get it. The flame expands outward to the surface in less than a second. I am ok so far. Now to do that the material would need to have a lot of momentum in the direction it is going, so how does it suddenly turn around and crash into itself on the other side? Not by gravity, or? Is there a pressure wave caused by the flame that travels along the surface and meets with itself on the other side, causing increased pressure and detonation as a result?

        I found that passage confu

      • I don't get it. The flame expands outward to the surface in less than a second. I am ok so far. Now to do that the material would need to have a lot of momentum in the direction it is going, so how does it suddenly turn around and crash into itself on the other side?>

        It is not the material itself that 'turns around', but rather the gas/plasma pressure increase that propagates (at nearly relativistic speeds, no less. The simulated star was earth-sized; imagine traveling to the other side of our planet

    • by Luyseyal (3154)

      I was going to ask "how do you see it if it doesn't fuse", but then I got smart and read the Wikipedia page on white dwarfs [wikipedia.org] which was really quite good, from a layman's perspective.

      Cheers and thanks for the wonderful comment,
      -l

  • "You seen one nova, you seen 'em all."
  • Looks like the 10 year visionary project [uchicago.edu] paid off right at the end. Long term financing was required along with faith in the project's people.
  • FTFB: the initial burst that is thought to be the source of much of the iron in the universe

    I always thought that iron was produced without the nova and that it was elements that are heavier than iron that were created by the blast. Am I wrong on this?
    • by 32Na (894547)
      I agree, (type II) supernovae actually destroy their iron core in order to create heavier nuclei from the new, neutron-rich environment.
      Here's a link:
      http://www.daviddarling.info/encyclopedia/R/r-proc ess.html [daviddarling.info]
      Here, they are simulating a type I supernova: a white dwarf that 'steals' mass from its neighbor until it reaches some critical mass, and we see a supernova.
  • or does anybody else have a sudden craving for pop corn?
  • What's fascinating to me is the behavior of the explosion front. At first it seems counterintuitive for it to 'burrow' towards the surface and burst asymetrically. But when you stop and think about it, that is the behavior you should expect - the expansion is the direction of least resistance, into regions of lower pressure.
  • What a waste of copmuter time and energy.
    Didn't they have a good 3d application.
    How about povray or 3d max joking..

    but only 3 sec thats almost nothing...

    1...2...3 and here is our electricity bill and hardware bill ping $1xx.xxx.xxx.-
  • If you need any help picturing what they're studying, this professor's here to tell you why a supernova would be totally awesome [nagt.org]!

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