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Frequency of supernovae in the universe

  1. Aug 12, 2007 #1
    Is it true that on an average day on Earth, thousands of supernovas happen some place in the universe?
     
  2. jcsd
  3. Aug 12, 2007 #2

    marcus

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    Nice thought isn't it? I would guess that's right, but I don't have figures.
    To be precise you'd need to specify some volume, like the Hubble volume.

    I'd like to know too. Maybe someone knowledgeable in this area will oblige.
     
  4. Aug 12, 2007 #3

    russ_watters

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    We can start with some quick order of magnitude calcs and tweak the numbers: If a typical galaxy has a hundred billion stars, 1% of which will go supernova, and the average lifespan of these is 5 billion years, there should be 1 every 5 years in any given galaxy. That seems a bit high, but that's just off the top of my head, so lets go with it for a start until someone comes up with better numbers....

    The Hubble Telescope has visual access to about 150 billion galaxies, so at 1 every 5 years in each, that's 30 billion a year or 82 million a day.
     
  5. Aug 12, 2007 #4

    marcus

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    jeez
    that is a lot of supernovas!
    what else can I say?
    thanks
     
  6. Aug 12, 2007 #5
    That's almost 1,000 every second...:eek:
     
  7. Aug 13, 2007 #6

    Wallace

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    I'm not sure of the precise figures but 1 SN in each galaxy every 5 years seems a little high, more like 1 in every 500 years or so I think, but that's only 2 orders of magnitude different, so not that much is astronomical terms.
     
  8. Aug 13, 2007 #7

    russ_watters

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    Once every few hundred years is more in line with what has been observed by humans the past couple of thousand years and is what I've heard before. That said:
    http://www.lbl.gov/Science-Articles/Archive/supernova-search.html

    Either way, yeah, that doesn't change the basic idea that supernovas happen very often in our observable universe.
     
  9. Aug 14, 2007 #8
    Oddly enough, I'm currently reading 'The Extravagent Universe' by Robert P. Kirshner (who appears to have spent a great deal of his early career looking for supernova) and I've just reached a page where he states "..If a supernova goes off once in a century per galaxy, that's roughly once in 5000 weeks, so if you want to see a nice fresh supernova at its brightest tonight you need to examine several thousand galaxies.." which pretty much tallies with what other people are saying here: 1 supernova every 100 years. Based on 150 billion galaxies, that works out at about 4.1 million/day or approx. 47/second.

    regards
    Steve
     
    Last edited: Aug 14, 2007
  10. Aug 16, 2007 #9

    mgb_phys

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    It's once every few hundred years for 'observable' supernovae - the actual rate is about 10x that. The majority of stars in our galaxy aren't visible because of the dust clouds near the centre.
     
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