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If I got the math right, then about 1 in every 32,000 stars in the universe goes supernova each year. That's scary. But I think I'm getting the math very wrong.

If I got the math right, then about 1 in every 32,000 stars in the universe goes supernova each year. That's scary. But I think I'm getting the math very wrong. edit: I guess my error might be related to confusing a probability factor with the number of incidents in a period. edit: The right answer is probably up to 1 in every 10bn stars go supernovae in the universe each year (or 1 in 10bn die and a fraction are supernovae). Thanks: yzydserd and zild3d

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Someone 1y ago
> If got the math right, then about 1 in every 32,000 stars in the universe goes supernova each year Can’t be right, can it? It would make the Sun (over 4 billion years old) an enormous outlier. It also would mean stars, on average, do not get very old. Over 10% of the stars that the ancient Greeks saw in the sky would have to have gone supernova since then.
- herendin2 1y ago
  > Can’t be right, can it? It would make the Sun (over 4 billion years old) an enormous outlier. Yes. That fact that I'm thinking made me think I was certainly wrong
- crag-jene 1y ago
  Not all stars can go supernova. Sol will never go supernova. Only very massive stars can—or stars that become very massive by absorbing other stars.
  - btilly 1y ago
    Binary white dwarf systems can also go supernova, even if the combined mass is not that large as far as stars go.
zild3d 1y ago
He mentioned a rough estimate of one per century per galaxy. Estimate for average stars per galaxy is 100 million, which would be 1 in 10 billion stars every year
yzydserd 1y ago
A star "lasts" about 10 billion years, so you'd expect about 1 in 10 billion stars to 'die' each year, but only a tiny proportion (the very largest) go supernova. Numbers are huge. Even tiny ratios mean something like 10-100 stars go supernova every single second somewhere in the universe. Sounds a lot? Only about 1 star per galaxy goes supernova per century. A lot of galaxies. Mindblowing.
- arp242 1y ago
  The lifespan of stars varies a lot by type and size, with largest stars having a very short life-span of maybe a few dozen million of years and small ones up to dozens of billions of years. I'm not sure what the average is.
- icehawk 1y ago
  So only 0.12% of all main sequence stars, have the mass that can become the most common type of supernova, and they apparently only last for about 100 million years.
- throwawaymaths 1y ago
  what's the rate of Type Ia supernovas? Higher I would guess? (n>=2-aries are common and medium mass main sequence stars are common, though it takes them a while to get to white dwarf)
  - icehawk 1y ago
    1/2 as common. https://astrobites.org/2022/04/16/template-post-9/#:~:text=Type%20II%20supernovae%20are%20about%202.4%20times,would%20be%20highly%20beneficial%20(see%20Figure%202). https://astrobites.org/2022/04/16/template-post-9/#:~:text=T...
- jibe 1y ago
  Wouldn’t the creation dates of stars be clustered around certain points in time. So the supernovas should also happen in groups?
- Tuna-Fish 1y ago
dostick 1y ago
Isn’t the answer infinity? We don’t know what’s beyond observed part of universe, and there’s infinity number of universes. If our emerged then there’s others.
- tialaramex 1y ago
  There is no reason to expect any particular number of universes. We've observed exactly one, this one, which had to exist or else we wouldn't be here to observe that it existed. Our universe is finite, so although it is unbounded (lacks edges) there aren't an infinite number of anything in it, galaxies, stars, M&Ms, grains of sand, atoms of hydrogen all finite.
  - atq2119 1y ago
    Has that really been established? The observable universe is finite, yes, but I wouldn't think that automatically implied that the universe as a whole is.
    - pixl97 1y ago
      Simply put we can't know and we can never know if the universe is flat. Now, if the universe has a curvature then we could use that as a baseline for the size of the universe, but as of so far we've not detected one.
- andyjohnson0 1y ago
  > and there’s infinity number of universes There is no evidence that there are a infinite number of universes. All we know of is the one we exist in. The many worlds interpretation of quantum mechanics posits that there are a very large number of non-interacting "worlds" which may or may not be the same as "universes". And if you meant "infinity number of galaxies" then that would require an infinite-size universe, and we don't know if that is the case for our universe. It could be, or it could be finite but unbounded.
  - dostick 1y ago

deleted 1y ago

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Someone 1y ago

> If got the math right, then about 1 in every 32,000 stars in the universe goes supernova each year Can’t be right, can it? It would make the Sun (over 4 billion years old) an enormous outlier. It also would mean stars, on average, do not get very old. Over 10% of the stars that the ancient Greeks saw in the sky would have to have gone supernova since then.

herendin2 1y ago
> Can’t be right, can it? It would make the Sun (over 4 billion years old) an enormous outlier. Yes. That fact that I'm thinking made me think I was certainly wrong
crag-jene 1y ago
Not all stars can go supernova. Sol will never go supernova. Only very massive stars can—or stars that become very massive by absorbing other stars.
- btilly 1y ago
  Binary white dwarf systems can also go supernova, even if the combined mass is not that large as far as stars go.

zild3d 1y ago

He mentioned a rough estimate of one per century per galaxy. Estimate for average stars per galaxy is 100 million, which would be 1 in 10 billion stars every year

yzydserd 1y ago

A star "lasts" about 10 billion years, so you'd expect about 1 in 10 billion stars to 'die' each year, but only a tiny proportion (the very largest) go supernova. Numbers are huge. Even tiny ratios mean something like 10-100 stars go supernova every single second somewhere in the universe. Sounds a lot? Only about 1 star per galaxy goes supernova per century. A lot of galaxies. Mindblowing.

arp242 1y ago
The lifespan of stars varies a lot by type and size, with largest stars having a very short life-span of maybe a few dozen million of years and small ones up to dozens of billions of years. I'm not sure what the average is.
icehawk 1y ago
So only 0.12% of all main sequence stars, have the mass that can become the most common type of supernova, and they apparently only last for about 100 million years.
throwawaymaths 1y ago
what's the rate of Type Ia supernovas? Higher I would guess? (n>=2-aries are common and medium mass main sequence stars are common, though it takes them a while to get to white dwarf)
- icehawk 1y ago
  1/2 as common. https://astrobites.org/2022/04/16/template-post-9/#:~:text=Type%20II%20supernovae%20are%20about%202.4%20times,would%20be%20highly%20beneficial%20(see%20Figure%202). https://astrobites.org/2022/04/16/template-post-9/#:~:text=T...
jibe 1y ago
Wouldn’t the creation dates of stars be clustered around certain points in time. So the supernovas should also happen in groups?
Tuna-Fish 1y ago

dostick 1y ago

Isn’t the answer infinity? We don’t know what’s beyond observed part of universe, and there’s infinity number of universes. If our emerged then there’s others.

tialaramex 1y ago
There is no reason to expect any particular number of universes. We've observed exactly one, this one, which had to exist or else we wouldn't be here to observe that it existed. Our universe is finite, so although it is unbounded (lacks edges) there aren't an infinite number of anything in it, galaxies, stars, M&Ms, grains of sand, atoms of hydrogen all finite.
- atq2119 1y ago
  Has that really been established? The observable universe is finite, yes, but I wouldn't think that automatically implied that the universe as a whole is.
  - pixl97 1y ago
    Simply put we can't know and we can never know if the universe is flat. Now, if the universe has a curvature then we could use that as a baseline for the size of the universe, but as of so far we've not detected one.
andyjohnson0 1y ago
> and there’s infinity number of universes There is no evidence that there are a infinite number of universes. All we know of is the one we exist in. The many worlds interpretation of quantum mechanics posits that there are a very large number of non-interacting "worlds" which may or may not be the same as "universes". And if you meant "infinity number of galaxies" then that would require an infinite-size universe, and we don't know if that is the case for our universe. It could be, or it could be finite but unbounded.
- dostick 1y ago