Talk:Neutron star

Pressure at/after/near collapse

Could the article mention that the core degeneracy pressure at collapse approaches the maximum possible theoretical pressure of P = pc² , where p is the density? 172.129.30.241 (talk) 01:19, 18 August 2010 (UTC) BG

1. Can the article give an approximate range for estimated core pressures in a neutron star? For starters wouldn’t the non-relativistic core pressure of a neutron star be given approximately by P(c) = KGM²/(πR⁴), where K is a constant dependant on the density profile, but nominally equal to 1. For 1.35 to 2.1 solar mass stars, this would give estimated pressures of about 1 X 10³⁴ to 2 X 10³⁴ kg/m². The magnitude of this approximate pressure is mind boggling. It would be equivalent to about the entire weight of the sun pressing down on 1 cm² at the earth’s surface. This is a sloppy calculation and maybe others could improve it. It would be nice if someone could give a better equation for core pressure or at least the results. Does someone have Tolman–Oppenheimer–Volkoff equation solutions for a neutron star? I don't accept the TOV equation but many others do.

2. To diverge, why should collapse of this type structure lead to a point singularity? If during collapse the mass not blown away is large enough to form a black hole, shouldn’t the resulting high temperature essentially convert all this mass into contained radiation? The basic pressure formula for this intense radiation would likely be P = pc² (where p is the equivalent mass density of the energy). This should prevent collapse to a singularity since this pressure has no limit and increases as 1/R³, faster than the increase of gravitational force. 172.162.242.8 (talk) 19:59, 23 September 2010 (UTC)BG

As was explained to you at talk:black hole, relativity can't be neglected when doing this calculation, as its effects dominate. That is why the Chandrasekhar and TOV limits occur.

Also as was explaiend to you at talk:black hole, Wikipedia really isn't the place to ask about this. I suggest asking on one of the physics newsgroups. --Christopher Thomas (talk) 22:56, 25 September 2010 (UTC)

Good idea. Your comments are welcome at http://www.physicsforums.com/showthread.php?p=2905538#post2905538 ````BG —Preceding unsigned comment added by 172.129.106.208 (talk) 00:29, 29 September 2010 (UTC)

Maybe you directed me to the forums as punishment. Perhaps some there believe a BH is made of chocolate pudding. Now I long for the days when conversations were dominated by singularity advocates. 172.163.115.55 (talk) 18:37, 29 September 2010 (UTC)BG

I directed you there because detailed discussion is on-topic/appropriate there, unlike here. No more, no less. There were several other venues mentioned in the banner at Talk:Black hole; by all means try some of the others if the forum is not to your taste. --Christopher Thomas (talk) 18:56, 29 September 2010 (UTC)

Yes. Radiation pressure of pc^2 or (pc^2)/3 shows why collapse should not occur in the core of a black hole. But it does not explain why collapse should not occur at the black hole surface. But based on E = mc^2, the absolute maximum pressure P that matter should be able to support is P = pc^2, where p is the density of the matter. Its interesting that neutron star cores at collapse approach this pressure.172.162.222.11 (talk) 13:18, 5 October 2010 (UTC)BG

It would be interesting to know if neutron star core collapse occurs at a pressure of (pc²)/3, at pc², or somewhere in between. Does anybody have this information or an estimate? Possibly it could be added to the article. 172.130.75.73 (talk) 19:42, 17 October 2010 (UTC)BG

Copyrighted section removed

I was bold and removed the Disrupted Recycled Pulsar section as it was copyrighted. The origin of this section was from this link http://www.scientificcomputing.com/news-DS-Einstein-at-Home-Citizen-Scientists-Discover-New-Pulsar-081210.aspx

Notice at the bottom of the article "Science Express, August 12, 2010". This section was added on August 31, 2010 as shown in this link: http://en.wikipedia.org/w/index.php?title=Neutron_star&oldid=382083718

Obviously a copyright violation. Good information if worded differently but until that is done, we can't have it on Wikipedia. —Preceding unsigned comment added by 97.112.196.161 (talk) 00:01, 1 September 2010 (UTC)

Question about rotation and life span

How come the slow down rate/ rotation occur after a century or million years when we all know that free neutrons undergo beta decay with a half-life of about 10 minutes and are not readily found in nature, except in cosmic rays.68.147.41.231 (talk) 04:55, 7 November 2010 (UTC)khattak#1

Neutrons within neutron stars are stable. A neutron star is compact enough that an equivalent number of electrons within it would have to have extremely high energies, due to being a degenerate gas. This makes it energetically unfavourable for neutrons to decay (the resulting proton plus electron would have more energy than the original neutron), so they don't. --Christopher Thomas (talk) 08:25, 7 November 2010 (UTC)

Neutrons are also found within nuclei. And they are stable there as well. Dauto (talk) 03:04, 5 February 2011 (UTC)

Reifying Language

The first paragraph has the following: "Neutron stars are very hot and are supported against further collapse because of the Pauli exclusion principle." The principle describes the force, it is not the force itself. Can this be rephrased so that it doesn't sound as if our theories cause the phenomena? —Preceding unsigned comment added by 24.22.166.163 (talk) 00:16, 10 December 2010 (UTC)

Neutron Star

The statement that "Neutron stars ... are supported against further collapse because of the Pauli exclusion principle." is incorrect. Pauli's exclusion principle is a very important physics principle, but in itself it does not generate the force that prevents a neutron star from further collapsing. There is a confusion here of a "principle" with a "force". — Preceding unsigned comment added by Macedonio5 (talk • contribs) 22:00, 4 February 2011 (UTC)

You're mistaken. The article is correct. Dauto (talk) 03:00, 5 February 2011 (UTC)

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Formation

I wish this section could be considerably improved. It doesn't really contain any information on how a neutron star is formed.

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— Preceding unsigned comment added by Macedonio5 (talk • contribs) 22:00, 4 February 2011 (UTC)

Cleanup for Properties section

The Properties section seems to have some discussion in it (e.g. the third paragraph calls the previous paragraph invalid.) RJFJR (talk) 18:03, 16 February 2011 (UTC)