Talk:Pair-instability supernova
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[edit] Questionable change?
The paragraph "For lower mass stars (about 100 solar masses and below), other conditions keep the star's core stable. Pair production does not cause an instability. These stars collapse in ordinary Supernova." was changed to "For lower mass stars (about 100 solar masses and below), the gamma rays are not energetic enough to produce electron-positron pairs, and if these stars become supernova they do so via other means.". I'm wondering if the latter is true - are electron-positron pairs not produced at all in regular supernovae? That seems unlikely to me. I would guess they are produced in inadequate numbers to cause the runaway reaction that leads to total explosion. --Keflavich 05:13, 13 May 2007 (UTC)
[edit] Energy source
So I'll ask a dumb question:
In a typical core-collapse supernova, the core is made of iron and any thermonuclear reactions would not produce a surplus of energy that could drive an explosion. So the supernova energy comes from the gravitational energy of the collapse, leaving a remnant behind due to the requirement to balance the energy. Is this right? If so, what generates the extra energy in the core needed to gravitationally decouple a pair-instability supernova? Does an explosive reaction occur outside the collapsing iron core?
This is unclear to me from the text. Thanks. — RJH (talk) 15:37, 15 May 2007 (UTC)
- Based on articles 1 and 3, a pair-instability supernova could not occur with an iron core. The explosion results from explosive burning of oxygen and silicon, which probably wouldn't occur if enough of the core had already burned. Anyway, the supernova described on this page really only applies to zero-metallicity population III stars. --Keflavich 18:10, 15 May 2007 (UTC)
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- Low metallicity, not zero; follow the refs out [1] and you find tables of how far up the metallicity scale the pair-instability effect can still happen. There's a plateau at which the pair instability effect happens for arbitrarily large mass stars (which at zero metallicity, will direct collapse to black holes via endothermic photodisintegrative processes). Beyond that a bit, the pair-instability effect stops entirely. Most of these are Pop III stars, but Eta Carinae and the SN 2006gy supernova are newer... Georgewilliamherbert 18:46, 15 May 2007 (UTC)
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- Thanks for pointing that out... I never even read the y axis before. --Keflavich 19:21, 15 May 2007 (UTC)
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[edit] Correct a reference
I'm new to Wikipedia, and so I'm not sure how to correct the Fryer link in the references section. arXiv.org states that documents should not be linked out of the cache, but rather against the main document entry page here: http://arxiv.org/abs/astro-ph/0007176v1
Wjhudson 17:10, 18 May 2007 (UTC) wjhudson
- You could have just edited the URL that shows up in the reference (it's located at the top, inline with where it first appears, in a macro that puts the [3] tag in and then puts the detailed ref at the bottom). I've made the change you list now. That was a good spot. Thanks for noticing that; I think the ref being the cached one was my fault. Georgewilliamherbert 20:02, 18 May 2007 (UTC)
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- Thanks George. It looks like you're also the person I need to thank for linking to my blog entry on SN2006gy in the external references section. I am happy you found it useful. Wjhudson 18:05, 19 May 2007 (UTC)wjhudson
[edit] Thermonuclear?
"As described in the introduction, the results of pair creation interactions are pairs of electrons and positrons. These particles are released into the star's core and usually recombine (releasing another gamma ray) in very short time periods."
Surely they annihilate themselves rather than recombine? Recombine suggests to me that a particle is left when the process is over. This of course leads to the question that is the runaway reaction that blows the star apart indeed a thermonuclear event as the introduction describes or matter/antmatter annihilation? Or is the reaction primarily thermonucear driven by the increasing temperature and pressure caused by the collapse associated with increasing pair production? --LiamE (talk) 16:46, 22 January 2008 (UTC)
- Recombination generally happens first for positronium (positron + electron "atom"), then after a series of level transitions the positron and electron annihilate in the center; normal positronium has a decay lifetime of something like 1 microsecond. However, I'd guess conditions inside a supernova are different (energetic) enough that the positron and electron probably do not form an atom before annihilating most of the time. --Keflavich (talk) 00:29, 17 February 2008 (UTC)
