How Many Supernovas Have Occurred Since the Big Bang?

[Spin_Network]

Can anyone point me how to: Work out the number of Supernova's that would have occurred 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.

 

[SpaceTiger]

Can anyone point me how to: Work out the number of Supernova's that would have occurred in the Universe from the big-bang up to the present time?

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?

 

[Spin_Network]

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?

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?

 

[misskitty]

I would assume it would be quite a few. Which type of supernova happens more often, type 1 or type 2?

 

[SpaceTiger]

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 )

Are you maybe talking about the Drake Equation?

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?

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.

 

[SpaceTiger]

I would assume it would be quite a few. Which type of supernova happens more often, type 1 or type 2?

In a spiral galaxy it's type 2, in an elliptical it would be type 1.

 

[misskitty]

Do we live in a spiral galaxy or an elliptical one?

 

[SpaceTiger]

http://solarsystem.nasa.gov/multimedia/gallery/MilkyWay.jpg

 

[Spin_Network]

I would assume it would be quite a few. Which type of supernova happens more often, type 1 or type 2?

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?

 

[misskitty]

That would make sense. Space Tiger that picture is awesome ! How big is our galaxy anyway? How many stars does it have?

 

[Spin_Network]

http://solarsystem.nasa.gov/multimedia/gallery/MilkyWay.jpg

Here's one through the eye of 'Michealangelo'

http://hubblesite.org/gallery/showcase/galaxies/index.shtml

click on spiral!

 

[SpaceTiger]

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.

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.

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?

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

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?

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.

 

[misskitty]

Spin that picture was really cool. I always loved seeing the pictures of the universe and planets and related topics.

 

[misskitty]

What causes matter to explode to create stars? WHy do elliptical galaxies have fewer stars then spiral?

 

[Chronos]

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

 

[SpaceTiger]

What causes matter to explode to create stars? WHy do elliptical galaxies have fewer stars then spiral?

Ellipticals form fewer stars. They still have many stars, but they formed them when they weren't elliptical galaxies.

 

[Labguy]

Ellipticals form fewer stars. They still have many stars, but they formed them when they weren't elliptical galaxies.

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.

 

[SpaceTiger]

They may form fewer, but they have more in number by far.

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.

 

[Chronos]

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.

 

[SpaceTiger]

There are, of course, small ellipticals, especially at larger redshifts.

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.

 

[Chronos]

I was thinking of this article, which I probably misinterpreted:
http://www.blackwell-synergy.com/links/doi/10.1046/j.1468-4004.2000.00210.x/html
Wouldn't be the first time that happened.

 

[matt.o]

ram pressure stripping is only effective in the cores of clusters, hence why we observe a higher elliptical to spiral ratio in the cores of clusters. ram pressure stripping is certainly not the sole mechanism for spirals morphing into ellipticals.

funnily enough, it has been proposed that spirals are also formed from mergers. I believe some ellipticals form from the merger of 2 galaxies, but I don't think it is true that all ellipticals formed from mergers.

 

[SpaceTiger]

ram pressure stripping is only effective in the cores of clusters, hence why we observe a higher elliptical to spiral ratio in the cores of clusters. ram pressure stripping is certainly not the sole mechanism for spirals morphing into ellipticals.

For less massive galaxies (inside or outside of clusters), one might expect starbursts to do the job of evacuating the dust and gas. I'm not 100% convinced by any of the theories at the moment, particularly in explaining the stellar dynamical differences between the two, but I agree that the merger hypothesis is enticing.

 

[matt.o]

well it seems that there is a correllation between mergers and starbursts as well!

 

[SpaceTiger]

well it seems that there is a correllation between mergers and starbursts as well!

Of course, an interaction would disturb the gas and dust quite a bit, likely initiating a starburst, but there are other ways to do the same thing. There's also a correlation between starbursts and AGN, and it's not clear which one is the cause and which is the effect (maybe both!). I suspect that there are multiple mechanisms that can set off a starburst, so there are probably multiple mechanisms that can evacuate the dust from the galaxy. It's hard to imagine that all these local dwarf spheroidals had their gas evacuated by a collision.