Talk:Gravitational collapse

fact?

The talk of black hole singularities states as if it is a fact, which is not the case. Although the idea of black holes are main stream, it is far from agreed upon. Another theory is what scientists call gravastars. There were more then a few articles in NewScientist if someone wants to add it, I will look it up myself if no one wants to do it. --ShaunMacPherson 15:24, 27 Apr 2004 (UTC)

gas clouds?

I came here looking for thermodynamic equilibrium of a gas cloud in zero gravity. This is talking about falling into a black hole. Stellar dynamics of core collapse might be relevant, but this is weird.

Yeah. Stellar evolution refers to gravitational collapse for clouds to hydrostatic equilibrium, and core collapse for dying stars. Potatoswatter 21:01, 15 February 2007 (UTC)

So basically,

this is an implosion on a huge scale? —Preceding unsigned comment added by 97.81.109.173 (talk) 01:56, 17 February 2008 (UTC)

Any implosion due to gravity. Everything in astrophysics is on a huge scale :v) . This article is misleading though, making it sound like a catastrophic event when that's not necessarily the case. Potatoswatter (talk) 18:51, 18 February 2008 (UTC)

nonsense

the line "An initial smooth distribution of matter will eventually collapse " is nonsense. How is it supposed to even move if the matter distribution is smooth? - User:Striver —Preceding unsigned comment added by 85.225.210.254 (talk) 09:52, 1 July 2008 (UTC)

Smooth except at the edges. Assume it's a cloud floating in space. Potatoswatter (talk) 16:40, 1 July 2008 (UTC)

It also depends on the definition of smooth. Tiny flucutations can evolve on long time scales and act as seeds for a larger collapse. — Preceding unsigned comment added by Schmidto (talk • contribs) 02:26, 21 February 2011 (UTC)

Gravitational Contraction

The history of Gravitational Contraction is the mechanism of energy release by Main Sequence stars.

An example of it mentioned is in page 3 of this pdf by Onno Pols and Frank Verbunt, Stellar modellers, and which is adapted from Van Den Heuvel a noted stellar modeller (as far as I'm aware) , Yet the wiki article does not appear to distinguish clearly that gravitational contraction is distinct from the case of collapse (collapse being a subset?) and the history of gravitational contraction is why stars shine but may lead to confusion as to the effects of gravitational contraction. IRWolfie- (talk) 13:10, 7 June 2010 (UTC)

I'm new to this topic, but I believe the mechanism of energy release by the Sun and other stars is nuclear fusion, not gravitational contraction. A few moments searching turns up the fact that in the 19th century, gravitational contraction was the prevailing theory for the origin of energy release by the Sun, but this was soon shown to be insufficient to explain the Sun's age. The true source remained unknown till the 1930s, when it was shown to be due to nuclear fusion.

However your second point, concerning the distinction between gravitational contraction and gravitational collapse is an important one, and this article appears to be a mish-mash of the two. This is a serious point which should be addressed. Mathglot (talk) 07:48, 24 July 2014 (UTC)

You really should read the entry on Stellar evolution. Energy production is a combination of gravitational contraction and nuclear fusion.aajacksoniv (talk) 14:50, 4 February 2015 (UTC)

Mathglot makes a good point. Not only that but the article (and mainstream analysis) doesn't even distinguish between the collapse of "matter", the collapse of protons, and the collapse of electrons. Our world and most stars consist of protons and electrons. Proton collapse logically happens significantly prior to electron collapse. For analysis of collapse neutrons should simply be considered a temporary bonding of a proton and an electron. The subject of matter collapse has not been investigated enough. No wonder black hole theory is such a mess and doesn't explain observations. To defend the singularity model, neutron star and black hole positron-electron jets and the Eddington limit being exceeded are somehow explained by external factors to the star! Proton collapse in the star core (resulting in a positron and energy release) explains both positron-electron jets, 2 solar mass maximum mass limit for a neutron star, and a hot star between 1.1 - 1.5 SR. 108.30.181.243 (talk) 16:53, 2 June 2016 (UTC)BG

References

Gravitational collapse simulation

I suggest to add external link:

• Simulation of gravitational collapse

Its wonderful to see the mathematical predictions of general relativity demonstrated in an animation, but does the final circle represent a singularity or finite size star? 108.30.181.243 (talk) 17:17, 2 June 2016 (UTC)BG

Do you mind?

Breny47 (talk) 19:34, 18 October 2012 (UTC)

Removed "Misleading" banner.

Removed the "Misleading" bullet dated Oct 2009 from the "Multiple issues" banner. It may well be that the article is misleading, but there are no inline templates indicating so nor any Talk page comment about it. Simply declaring the whole article "misleading" over five years of edits seems unhelpful, and, uh, misleading. I've removed it.

If someone more knowledgeable than I am about this topic can affirm that the article is in fact misleading, please restore the banner to the article, and add some in-line references (or comments here) about it. Mathglot (talk) 07:05, 24 July 2014 (UTC)

Tidy-up - please check for accuracy

I've tried to make the article more readable, but it's possible that I've over-simplified or introduced inaccuracy, so if you know the subject please check! Snori (talk) 23:16, 25 June 2015 (UTC)

Fundamental problem with conventional analysis: Collapse should mean proton collapse.

The article presently states: According to Einstein's theory, above the TOV limit no known form of cold matter can provide the force needed to oppose gravity in a new dynamical equilibrium. Hence, the collapse continues with nothing to stop it.

For starters, a fundamental problem with this analysis is that "matter" just doesn’t collapse; proton collapse should occur before electron collapse, and this is not addressed. If proton disintegration occurs prior to electron collapse, the reaction should be: proton → positron + 938MeV. Allowing for some neutrino and gamma production, this should result in a 450MeV (initial temperature) electrically neutral positron-electron plasma. This plasma will heat everything around it or escape the star. A 450MeV (initial temperature) positron-electron plasma, caused by collapsing protons, explains neutron star mass being limited to about 2.0 SM, the massive positron-electron jets emanating from neutron stars and 'black holes', TeV cosmic rays, the Eddington limit sometimes being exceeded (a jet from within the star heats material outside the star), the main source of radio noise associated with jets, and why stars with jets like IGR J11014-6103 are radio quiet. A hot star greater than 1.1 Schwarzschild radius could eject positron-electron plasma and still appear black by the tests we use. These stars should have similar chemical constituency as conventional stars and neutron stars (just protons, neutrons, ions, and electrons), but with a tiny percentage of positron generation providing the heat and fireworks. (A high pressure star like a 5SM black hole might have no ions.) I used to believe nucleus collapse in neutron stars or 'black holes' should lead to quark production but the positron-electron jets indicate a different story. Structurally these stars are much like conventional visible stars just much hotter and denser. Virial energy provides support and the TOV equation does not apply. This 'black hole' star does NOT contain all light, nor even positrons/electrons above a certain temperature, but has the quirk you probably normally don't see it because of red shift, like many one-sided astrophysical jets. But you do see the positron-electron jets and everything associated with them, including gamma. Consider a hot star of radius 1.1 - 1.5 SR: Above a certain temperature positron-electron plasma would escape the star but protons and ions could not; the positron-electron energy ejection could regulate star radius. Interesting that if a star like this would become hotter as radius decreases, there would also be more red shift effect on escaping radiation. My guess is star radius would vary somewhat and be >1.2 SR. If there is no jet this star could still ooze positron-electron plasma.

Logically when matter collapses there should be a hierarchy of collapse, probably due to smaller particles having higher energy density than larger particles. First protons (or antiprotons) collapse, then positrons and electrons collapse, then neutrinos collapse, and so on. 108.30.181.243 (talk) 17:33, 28 May 2016 (UTC)BG

Please use the Talk page to discuss improvements to the article. This is not the place to expound on your ideas about the fundamental problems with Einstein's theory, interesting though they may be. Instead, try submitting it to a peer-reviewed journal such as Physical Review Letters or Classical and Quantum Gravity. Perhaps they'll publish it or give you suggestions for improvement. Mathglot (talk) 19:51, 15 June 2016 (UTC)

Well, when matter collapses does proton collapse happen prior to electron collapse, or do protons and electrons collapse simultaneously? The article can not be significantly improved unless this fundamental issue is addressed. 151.202.5.131 (talk) 13:58, 19 June 2016 (UTC)BG

Gap in the range of possible compact star radius

Removed citation request and qualified the statement. The article sensibly says a star smaller than 1.0 Schwarzschild radius doesn’t make sense. Its accepted that 2.0 solar mass neutron stars are probably about 2.0 Schwarzschild radius. The article states when the TOV limit is exceeded no known form of COLD matter can provide the force needed to oppose gravity, and collapse must also happen for a radius smaller than 1.0 Schwarzschild radius, with the outcome in either case being a collapse to a singularity. At least that leaves a gap for a HOT star between 1.0 - 2.0 Schwarzschild radius. Theoretically a 1.1 – 1.5 Schwarzschild radius star supported by viral energy would capture light (if only by absorption) although high energy leptons and gamma would escape. As a star gets smaller (say below 1.5 SR) containment becomes more effective, and depending on whats being measured, a star would appear to turn off, while containing virial energy better too. Its probably going to boil down to if relativistic jets originate external to a neutron star or from within a neutron star. See IGR J11014-6103 Jet in Astrophysical jet. I think a big problem with the conventional singularity model is not that collapse happens below 1.0 SR, but that a collapsing star never gets smaller than at least 1.1 SR. 108.30.181.243 14:16, 29 May 2016 (UTC)BG

Wiki Education assignment: 4A Wikipedia assignment

This article was the subject of a Wiki Education Foundation-supported course assignment, between 13 February 2023 and 12 June 2023. Further details are available on the course page. Student editor(s): ReignInSupremeDarkness (article contribs). Peer reviewers: BlakeMalloy, Bdowell3.

— Assignment last updated by Lzepeda12 (talk) 21:07, 26 April 2023 (UTC)