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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)
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)
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
"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)
This article doesn't explain why a black hole is not formed, and what triggers the sudden occurrence of the pair-instability state. Andrewjlockley ( talk) 15:48, 27 February 2010 (UTC)
This article about sn2007bi is interesting but maybe not directly usable in WP. It might point to something more suitable. 66.127.53.162 ( talk) 08:43, 22 April 2010 (UTC)
I'm unclear why this is relevant. I do not believe the reduction in gamma mean free path with increasing temperature is responsible for the instability. Rather, it is the fact that increasing temperature shifts the equilibrium between gammas and pairs in favor of pairs. This reduces gas pressure and contracts and heats the star, shifting the equilibrium yet further in favor of pairs, and so. So I think the discussion of mean free paths is irrelevant and unhelpful. Yaush ( talk) 18:46, 1 March 2011 (UTC)
I've made a few edits to this article with the intent to construct a more readable narrative from (what seem to me to be) somewhat disconnected scientific observations.
Not pretending to have any scientific expertise, in this area or otherwise, I have endeavored at all times to maintain the scientific content, and avoided making edits to material appearing to admit of more than a single correct explanation.
If there are times when I have erred, I apologize, but I do think that the article could be made rather more comprehensible to a layperson without compromising its scientific rigor. Drolz 09 03:37, 17 October 2013 (UTC)
Nuclear fusion in a star's core produces gamma ray photons. When such a photon interacts with an atomic nucleus, it may convert into a positron and electron; the positron-electron pair then annihilate, changing back into a photon. At very high temperatures, pair production becomes much more frequent, to the point that positron-electron pairs are created faster than they can annihilate. When the stellar core reaches these temperatures, it begins "losing photons" to pair production. This causes the photon pressure to drop. Since photon pressure is what supports the core against gravity, the drop allows gravity to compress the core more tightly, which raises the temperature further.
As temperature rises in the core, two things happen. First, pair production becomes even more prevalent. Second, nuclear fusion accelerates. Normally, the increase in fusion would result in increased photon pressure, causing the core to expand and cool. The loss of photon pressure to pair production disables this safety valve, so the core continues to shrink. The result is a runaway fusion reaction, which rapidly heats the core to the point that its thermal energy overcomes gravity. The core then explodes, tearing apart the entire star. 129.74.116.38 ( talk) 16:02, 27 January 2014 (UTC)
The remnants section contradicts the information given previously in the article, which says the existence of a remnant is conditioned on the mass of the star. Given that the evolution by mass paragraphs above describe the remnant for each mass range, I think this section should probably be deleted as redundant.
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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)
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)
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
"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)
This article doesn't explain why a black hole is not formed, and what triggers the sudden occurrence of the pair-instability state. Andrewjlockley ( talk) 15:48, 27 February 2010 (UTC)
This article about sn2007bi is interesting but maybe not directly usable in WP. It might point to something more suitable. 66.127.53.162 ( talk) 08:43, 22 April 2010 (UTC)
I'm unclear why this is relevant. I do not believe the reduction in gamma mean free path with increasing temperature is responsible for the instability. Rather, it is the fact that increasing temperature shifts the equilibrium between gammas and pairs in favor of pairs. This reduces gas pressure and contracts and heats the star, shifting the equilibrium yet further in favor of pairs, and so. So I think the discussion of mean free paths is irrelevant and unhelpful. Yaush ( talk) 18:46, 1 March 2011 (UTC)
I've made a few edits to this article with the intent to construct a more readable narrative from (what seem to me to be) somewhat disconnected scientific observations.
Not pretending to have any scientific expertise, in this area or otherwise, I have endeavored at all times to maintain the scientific content, and avoided making edits to material appearing to admit of more than a single correct explanation.
If there are times when I have erred, I apologize, but I do think that the article could be made rather more comprehensible to a layperson without compromising its scientific rigor. Drolz 09 03:37, 17 October 2013 (UTC)
Nuclear fusion in a star's core produces gamma ray photons. When such a photon interacts with an atomic nucleus, it may convert into a positron and electron; the positron-electron pair then annihilate, changing back into a photon. At very high temperatures, pair production becomes much more frequent, to the point that positron-electron pairs are created faster than they can annihilate. When the stellar core reaches these temperatures, it begins "losing photons" to pair production. This causes the photon pressure to drop. Since photon pressure is what supports the core against gravity, the drop allows gravity to compress the core more tightly, which raises the temperature further.
As temperature rises in the core, two things happen. First, pair production becomes even more prevalent. Second, nuclear fusion accelerates. Normally, the increase in fusion would result in increased photon pressure, causing the core to expand and cool. The loss of photon pressure to pair production disables this safety valve, so the core continues to shrink. The result is a runaway fusion reaction, which rapidly heats the core to the point that its thermal energy overcomes gravity. The core then explodes, tearing apart the entire star. 129.74.116.38 ( talk) 16:02, 27 January 2014 (UTC)
The remnants section contradicts the information given previously in the article, which says the existence of a remnant is conditioned on the mass of the star. Given that the evolution by mass paragraphs above describe the remnant for each mass range, I think this section should probably be deleted as redundant.