Frequency of supernovae in the universe

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Is it true that on an average day on Earth, thousands of supernovas happen some place in the universe?
 

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  • #2
marcus
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Is it true that on an average day on Earth, thousands of supernovas happen some place in the universe?
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.
 
  • #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.
 
  • #4
marcus
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so at 1 every 5 years in each, that's 30 billion a year or 82 million a day.
jeez
that is a lot of supernovas!
what else can I say?
thanks
 
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so at 1 every 5 years in each, that's 30 billion a year or 82 million a day.
That's almost 1,000 every second...:eek:
 
  • #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.
 
  • #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:
In an experiment involving an automated telescope and a sensitive electronic detection system, members of LBL's Automated Supernova Search team have found 20 supernovas, most of them in the last three years. Analysis of the data suggests that supernovas occur at least once every 30 years in galaxies like our own, and maybe even more often. In the past, supernovas were thought to occur in Milky Way-type galaxies no more than once in 100 to 300 years.
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.
 
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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
 
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  • #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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