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Re: How can neutron stars form?



First, a little background. Stars support themselves against gravitational
collapse with mostly gas pressure (radiation pressure also contributes). Stars
consist mostly of hydrogen and some helium. The gas of hydrogen and helium is
so hot that the hydrogen and helium are ionized. Thus, the gas consists
predominantly of free nuclei (mostly hydrogen and some helium nuclei) and free
electrons. In main sequence stars, the nuclei/electron gas acts like an ideal
gas, even at their cores. The ideal gas law is a classical law. Quantum
effects are not needed to explain the behavior of an ideal gas.

In neutron stars, the gas is so compressed that the ideal gas law no longer
applies to the gas. Quantum effects become important because the particles are
squeezed so close together. Nuclear forces are short range forces, so an
electron and a proton have to be really close to each other before they can
combine to produce a neutron. Conditions in the neutron star satisfy this
requirement.

______________________________ Reply Separator _________________________________
Subject: How can neutron stars form?
Author: "phys-l@lists.nau.edu: Forum for Physics Educators"
<PHYS-L@LISTS.NAU.EDU> at Internet
Date: 5/20/99 10:35 AM


One explanation I have read regarding the formation of neutron stars is
that as the gravitation force compress the massive stellar matter beyond
the repulsive force of the electrons that the electrons are "driven" into
the nucleus of the atom and hit protons to form neutrons (hence neutron
stars).

This seems to contradict quantum theory. Electrons are already be
attracted to the nucleus because of their opposite electrical charge. If
the reason electrons don't fall into the nucleus is a "quantum exclusion"
(my Dad's explanation) as opposed to satellite-like orbital velocity then
how can this be? It's either an "exclusion" (a disallowed orbital jump?)
or it's not?

I could see an explanation that it only happens under tremendous pressure
or at high temperatures but it also seems confusing that the
gravitational force (10^40 times weaker than the electrical force) can do
want electrical attraction can't?

Sincerely,

Lee Wilmoth Lerner
Fairhope High School, Fairhope, AL USA Email via:
lw.lerner@juno.com
=93But I don't have to know an answer. I don't feel frightened by not
knowing things,
by being lost in the mysterious universe....=94 -- Richard Feynman
"...unless, of course, I have a test" -- LWL

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