Multiple orgasm supernovas

[Martin]

SciAm article about this

http://www.sciam.com/article.cfm?id=brightest-supernova-may-reignite

 

can possibly get two supernova explosions from same star, remote possibility of three.

 

Brightest supernova on record SN 2006gy

observed last year, over 100 solar mass star.

this may have left a remnant that can re-explode and may do so within a few years. If it does, should be very interesting to observe.

 

an important mechanism here is called "pair-instability", something qualitatively different happening in the core of a star when it reaches a certain temperature threshhold (the light starts producing electron-antielectron pairs)

Seems worth understanding. I forget if we have a thread about it. If not it could be discussed here.

[Mr Skeptic]

"Orgasm"? I guess the analogy is correct, especially if the material spewed out is required for life.

 

Now there is an effect of quantum at the macro level, eh?

[Reaper]

Nice! So I guess a first supernova in these stars doesn't really throw off enough material to prevent a second collapse, does it.

[Martin]

Nice! So I guess a first supernova in these stars doesn't really throw off enough material to prevent a second collapse, does it.

 

Exactly. I'd like to understand this stuff better. There is a mechanism that I just heard about recently that may play a role called "pair instability".

 

I don't remember if we have discussed it. Do you happen to have encountered it?

 

there is a temperature threshold above which a lot of the gamma photons in the core have sufficient energy so that a pair of them can create an electron positron pair.

 

so this new scattering reaction kicks in and ties up a lot of the light in this additional process and it makes the core more OPAQUE---the scattering interferes with the gamma energy getting out of the core and percolating on up thru the outer layers

 

I think this may have something to do with either how these huge stars form in the first place, or with how they get thru their red giant phase without blowing off so much of the outer layer as you would expect---so there is more to collapse eventually, when they burn out.

 

I've been busy and no time to get straight on the latest giant star lore. If you know some more please contribute it.

[Mr Skeptic]

I thought that supernovae ware caused when the core of the star collapsed into a black hole, releasing a shockwave that blasted the remainder of the star appart. That can only happen once though, so I must be missing something here.

[Martin]

I thought that supernovae ware caused when the core of the star collapsed into a black hole, releasing a shockwave that blasted the remainder of the star appart. That can only happen once though, so I must be missing something here.

 

there are several supernova mechanisms described in the literature.

a very common one is when a large star burns out and collapses to a NEUTRON STAR, and the shockwave blows off most of the outer layers

 

(actually the shockwave is believed to partly be caused by a huge wind of neutrinos, in such abundance that they exert force. it is more complicated than just saying shockwave suggests but that is a good first approx)

 

what we are learning is that in some very large stars, the shockwave is not powerful enough to blow all the outer stuff off

 

so a substantial part remain and settles back down on the dead core

 

the dead core is still very hot and not dense enough yet to collapse to a black hole (in some cases it never does, it just stays in some compact form of matter)

 

so the crud that didnt blow away settles down on the dead core and apparently, according to these new reports, can still have enough mass to make another supernova!

 

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BTW Skeptic you should know about the OTHER important mechanism where there is a double star system. One star is already dead and compact, say mostly carbon and oxygen, but not yet at the 1.4 solar limit (the Chandra limit)

and then the other star goes red giant and expands and crud rains down onto its compact partner until it builds up to the critical mass. and then the compact partner blows. presumably when it exceeds the 1.4 solar mass limit

That is the SN Ia kind. The Type 1-A that we are always hearing about.

 

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SNe can involve collapse all the way to hole, as you said in your post, but they don't have to.

they can happen when there is just collapse to neutron star

[Mr Skeptic]

Ah, thank you. The type 1A supernovae (standard candles) are indeed the ones I was thinking of. So that's why they are always the same brightness; they're right at the limit to become a black hole. Is a supernova in general just a stellar explosion?

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Would the multiple orgasm supernovas be more useful for seeding heavy matter than other types, perhaps due to exploding sooner, or releasing more matter?

[Martin]

Ah, thank you. The type 1A supernovae (standard candles) are indeed the ones I was thinking of. So that's why they are always the same brightness; they're right at the limit to become a black hole. Is a supernova in general just a stellar explosion?

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Would the multiple orgasm supernovas be more useful for seeding heavy matter than other types, perhaps due to exploding sooner, or releasing more matter?

 

Not quite. They are more or less at the

Chandrasekhar limit of 1.4 solar masses.

 

This is not the limit to become a black hole (what you said) but is more like being at the limit to become a neutron star.

 

the best thing is to read

http://en.wikipedia.org/wiki/Supernova#Type_Ia

 

it is short and concise.

 

an accreting white dwarf is a dead star---typically made of carbon and oxygen---which is gathering mass from a partner like a red giant.

 

1.4 solar is the most mass that can exist as normal matter

 

but the process is not just a simple collapse to neutron star (neutron matter is the next most dense phase from normal matter)

 

in Type IA what happens is that as 1.4 solar is approached, the carbon etc suddenly STARTS FUSION into stuff like nickel and iron

 

it is an actual thermonuclear explosion that happens around the Chandra limit

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this is a differnt mechanism from Type II, more common, giant star iron core collapse------it just happens that the Chandra limit is involved in both cases

 

IN NEITHER CASE IS COLLAPSE TO BLACK HOLE TYPICAL

more typical is collapse to neutron matter, or the thermonuclear explosion I mentioned.

 

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what you said however captures the basic idea well and gets the picture right.

[Mr Skeptic]

OK, thanks for teaching me. It seems I knew less astronomy than I thought!

[Martin]

OK, thanks for teaching me. It seems I knew less astronomy than I thought!

 

I didnt mean to sound like a teacher, but that is how it came out. What I mainly suggest is delving into that Wikipedia article on supernovas. they are extremely interesting.

 

Wikipedia is not always reliable but as far as I could tell that article is OK and as far as I can recall whenever I have looked at their astrophysics it has been OK. Good luck if you get further into it!