# Talk:Neutron star

## Equation appears to be dimensionally incorrect

The equation

${\displaystyle BE={\frac {885.975\,M_{x}}{R-738.313\,M_{x}}}}$

appears to have mixed dimensions in the denominator.
R has a dimension of length
${\displaystyle M_{x}}$is dimensionless — Preceding unsigned comment added by 50.45.15.139 (talkcontribs)

That equation is only valid if it has R in meters. The numbers 885 and 738 have units of meters. 00:51, 26 September 2016 (UTC)

## Strong force supports neutron stars against collapse

The article's editors continually write that neutron degeneracy pressure supports the neutron star against collapse. This is mostly untrue and should not be the sole reason given here. The editors are generally working from the false analogy that if a white dwarf is supported by electron degeneracy pressure, the neutron star must be supported by neutron degeneracy pressure. Note that none of their sources actually state that neutron degeneracy pressure supports the star - it's just "assumed."

Real neutron stars are supported against collapse mostly due to the strong nucleon-nucleon force. (No, the strong force does not act only in attraction - see https://en.wikipedia.org/wiki/Nuclear_force.) At the short nucleon-nucleon distances within the core of a neutron star, the strong force will act to repel nucleons (here, mostly neutrons) from one another. This repulsion - unrelated to degeneracy pressure - is stronger than degeneracy pressure within neutron stars. It supports the neutron star against collapse.

Sources: http://www.astro.princeton.edu/~burrows/classes/403/neutron.stars.pdf (page 3) "...using the relativistically correct equation of hydrostatic equilibrium (eq. (5)), and assuming a non-interacting degenerate gas of neutrons, Oppenheimer & Volkov (1939) derived a maximum neutron star mass of 0.7 M⊙, ∼eight times smaller. Observed neutron-star masses are clearly larger than this. The reason is that the strong repulsive nuclear force trumps neutron degeneracy pressure by a wide margin, resulting in less compact and more rigid structures supported by a stiffer EOS."

https://www.astro.umd.edu/~jph/A320_White_Dwarfs.pdf (page 10) "At densities of ρ ∼ 10^15 g cm−3, neutrons are not an ideal gas. These are the densities we find within an atomic nucleus, and the neutrons interact with one another via the strong force. Thus we see that to model neutron stars we need the TOV equation and an equation of state that includes not only degeneracy but the nuclear forces between the neutrons."

http://www.aanda.org/articles/aa/full/2001/46/aa1755/aa1755.right.html "The EOS is predominantly determined by the nuclear (strong) interaction between elementary constituents of dense matter."

http://www.rpi.edu/dept/phys/Courses/Astronomy/NeutStarsAJP.pdf Demonstrates that the strong force must be considered. The overall picture is not simple and not totally understood, as our knowledge of nucleon-nucleon interactions is incomplete.

I look forward to seeing discussion of the strong force's role permanently and prominently displayed in this article.

60.45.238.24 (talk) 15:28, 4 October 2016 (UTC)

Well with the nuclear force (which has slightly different semantics to the strong force) it is assumed that quantum degeneracy (hence Pauli's exclusion principle) is responsible for repulsive force between nucleons. But papers also postulate an additional negative nuclear force to account for neutron stars over about 0.7 solar masses. So I guess this could also be added, but if you do so please reference with inline citations! I think that is why it gets removed. If you don't know how to do this then ask me how. --Jules (Mrjulesd) 21:29, 4 October 2016 (UTC)

## Jargon needs definitions or links

The terms AP4, MS2, and "(for EOS FPS, UU, APR or L respectively)" are used with no definitions nor links to anything which might explain them. It makes those passages less than helpful.

P.S. to the authors: Thanks for an otherwise nice article. — Preceding unsigned comment added by Oldmeat (talkcontribs) 01:36, 1 March 2017 (UTC)

## Source of energy?

As we all know, with regular stars, nuclear fusion takes place place in their cores, and this nuclear fusion is what produces the energy emitted thereby.

Neutron stars also produce protons, but I wouldn't guess that nuclear fusion is taking place in their cores.  Would I be wrong to assume it's not?  And, assuming I am correct to guess that there is no nuclear fusion taking place therein, the question then remains: what produces the energy emitted by neutron stars?