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Supernova Probabilities

  1. Apr 10, 2005 #1
    Can anyone point me how to: Work out the number of Supernova's that would have occured in the Universe from the big-bang up to the present time?

    Basically I want a good idea of how many Type 1 or type 2 supernova's have probably occured, thanks.
     
  2. jcsd
  3. Apr 10, 2005 #2

    SpaceTiger

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    That's a pretty complicated problem. From historical records, you can estimate the rate of supernovae in the Milky Way, but we expect the rate to be different from galaxy to galaxy, as well as at different times in the history of the universe. Is this being asked for a class or are you just curious?
     
  4. Apr 10, 2005 #3
    The question is based on something I have been pondering, (nothing to do with class or homework as such). What I am pondering is relative to the principle for the estimation of possible life evolving planets, I know that some guy had formulated how to estimate 'probable' life forming planets(forget his name ), but anyway, I was going to try and use his principle, with the data I hoped to gain from knowing the probable amount of Supernova's, to estimate the:Total number of Life based Planets wiped out by SUpernova's?

    A sort of database on how many civilizations 'may' have been previous to ours?
     
  5. Apr 10, 2005 #4
    I would assume it would be quite a few. Which type of supernova happens more often, type 1 or type 2?
     
  6. Apr 10, 2005 #5

    SpaceTiger

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    Are you maybe talking about the Drake Equation?


    To wipe the life off a planet, a supernova would have to occur in their parent star or very close to it. In other words, that wouldn't restrict things very much. Gamma-ray bursts probably pose a bigger threat than supernovae, but they're still pretty poorly understood.
     
  7. Apr 10, 2005 #6

    SpaceTiger

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    In a spiral galaxy it's type 2, in an elliptical it would be type 1.
     
  8. Apr 10, 2005 #7
    Do we live in a spiral galaxy or an elliptical one?
     
  9. Apr 10, 2005 #8

    SpaceTiger

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  10. Apr 10, 2005 #9
    I may wrong here, but I think spiral Galaxies are older, and therefore Type 2 would be more common. Newer Galaxies should have more Blazers than Supernova's, and as there is a likelyhood of there being 'less' civilizations,until at least the Blazers have waned.

    Actually come to think about it:We are Made of Stars, it may be that life can only form after enough Stars have gone 'nova' and distributed its 'bits' to the surrounding calm Spiral Galaxy?

    So effectively, the signiture of Supernova's may be where we should be looking for 'lifeforms', given time to evolve, if we knew that a Star went Supernova, say 1 million or 10 million years ago, the surrounding part of this area, would be the ideal place to look for evolving lifeforms?
     
  11. Apr 10, 2005 #10
    That would make sense. Space Tiger that picture is awesome :bugeye:! How big is our galaxy anyway? How many stars does it have?
     
  12. Apr 10, 2005 #11
  13. Apr 10, 2005 #12

    SpaceTiger

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    It's not really a matter of age, though in general the opposite would be true (younger galaxies usually have more type 2). The reason is that type 2 supernovae come from the explosion of young massive stars, while type 1 SNe are thought to be old white dwarfs that have accreted enough matter to explode.

    The reason that ellipticals have only type 1s (for the most part) is that they no longer form many stars. The reason that they don't form many stars is that they have very little gas and dust. Spirals, on the other hand, are actively star-forming, so they have a lot of young stars exploding.


    A nova is something different, but the rest of what you said is basically correct.


    I don't think a single supernova can enrich a planetary system enough to initiate life. Usually it's the combined effect of many supernovae over time.
     
  14. Apr 10, 2005 #13
    Spin that picture was really cool. I always loved seeing the pictures of the universe and planets and related topics.
     
  15. Apr 10, 2005 #14
    What causes matter to explode to create stars? WHy do elliptical galaxies have fewer stars then spiral?
     
  16. Apr 10, 2005 #15

    Chronos

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    Matter does not explode to form stars, it gravitationally clumps until it becomes so dense and hot that a fusion reaction is initiated in the center of the collapsing gas cloud. Supernova are thought to play a very important role in star formation in galaxies. Gravitational collapse is believed to be triggered by shock waves generated by supernova. Note: Elliptical galaxies typically have more stars than spirals. Here is another pretty galaxy photo [it's my screensaver]:
    http://imgsrc.hubblesite.org/hu/db/2003/24/images/a/formats/1280_wallpaper.jpg
     
  17. Apr 10, 2005 #16

    SpaceTiger

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    Ellipticals form fewer stars. They still have many stars, but they formed them when they weren't elliptical galaxies. :wink:
     
  18. Apr 10, 2005 #17

    Labguy

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    They may form fewer, but they have more in number by far. Most ellipticals are thought to have formed from galactic mergers of two or more spirals and/or even gobble up an older elliptical or two. M 87 is a grand example with more than 10,000 globular clusters, many of which can be seen in an old (famous) photo by David Malin, AAO. There is a black hole in M 87 estimated at 3 billion solar masses.
     
  19. Apr 10, 2005 #18

    SpaceTiger

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    I wasn't disagreeing with Chronos, I was explaining to misskitty what I meant. The popular theory of ellipticals forming by mergers is still not observationally verified, so we need to keep alternatives in mind. In particular, ram pressure stripping may explain how they lost a lot of their gas. Also, M87 is an extreme outlier and an example of a cD galaxy. Most clusters have a bright and massive elliptical galaxy at their center, but most elliptical galaxies are not cD. In fact, if you include dwarf ellipticals in (or, even further, dwarf spheroidals) in that calculation, then ellipticals may even come out with fewer stars on average. I don't think we have particularly good statistics on either of those types yet, however.
     
  20. Apr 10, 2005 #19

    Chronos

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    I did not take exception, nor perceive any disagreement, with what ST was saying. Just hoping to clarify. The largest ellipticals have more stars than the largest spirals. It is thought that large ellipticals result from mergers. When Andromeda and MW merge, it is believed an elliptical galaxy will result. There are, of course, small ellipticals, especially at larger redshifts. That does is not very meaningful in my mind.
     
  21. Apr 11, 2005 #20

    SpaceTiger

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    We don't really know anything about small ellipticals at large redshifts. In fact, the smallest ones can only be seen in the local group. That's why the statistics are so poor. However, you're absolutely right that the biggest ellipticals are bigger than the biggest spirals.
     
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