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Posted by Michael Wright on November 27, 2000 17:34:13 UTC

First I have to explain degenerate matter to address some of these questions.

If a gas is very dense, all of the lower energy levels become occupied by electrons and the gas is termed "degenerate." In a degenerate gas the electrons cannot slow down because that would decrease its energy. It can't decrease its energy because all of the lower energy levels are taken. It can only speed up if it can absorb enough energy to leap above the very highest occupied energy level to an unoccupied one.

This has two effects on two core of a star:

First, the degenerate gas resists compression. To compress the gas, we must push against the moving electrons and that would take tremendous effort because we would have to change their energy by boosting them to the top of the energy ladder. Thus a degenerate gas can take on the consistency of hardened steel.

Second, the temperature of the degenerate gas does not affect its pressure. This is because most of the energy from heating up the gas would go to speeding up the motions of the nuclei and not the electrons.
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A White dwarf is characterized by its degenerate electrons preventing further collapse.

A Neutron star is characterized by its degenerate neutrons (which require far greater pressure to become degenerate but act in a very similar manner than degenerate electrons) preventing further collapse.

A Black Hole is characterized by the fact that no known force can stop its collapse.
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"1.Does the star which form the black hole become a white dwarf, then a neutron star, then a black hole?" - MrOKL

I think your first question is if the star is near the mass limit, does it take longer to go from stage to stage? I think it would, because less mass means less gravity and less pressure. Less gravity and less pressure mean the star collapses slower. A star having just barely enough mass to be destined to be a neutron star might 'hang' as a white dwarf for a very short time while it is building up pressure, but I don't think that it would last very long.


"2.if so, does the impact of each "state"(eg. solid, liquid, gas) of the star affect the other state?
eg. white dwarf has some impact on the neutron star " - MrOKL

I don't understand the question (sorry).


"3.how does each state move from one state to another?
eg. Solid to liquid: Atoms/molecules drift further apart" - MrOKL

If we have a very massive star (one that will become a black hole) and its core begins to collapse, the density quickly reaches that of a white dwarf. In fact, for a second it *is* a white dwarf. But its weight is too great to be supported by the degenerate electrons - the collapse continues.
The atomic nuclei are broken apart by gamma rays and almost instantly the rapidly increasing pressure forces the freed protons to absorb electrons and become neutrons. In a fraction of a second the collapsing core becomes a contracting ball of neutrons. Thus for a short time it *is* a neutron star.
But the star is too heavy to be stopped by degenerate neutrons, and (presumably) collapses into a black hole.


"4.what issit for the star?
the protons, electrons first leave the star due to gravity? does it even leave the star? since the gravity slowly grows as it enters each state, where do the protons/electrons go? it cant leave the star(neutron star)[mebbe its a misconcept that i think a neutron star is totally made up of neutrons]" - MrOKL

The first part of your question is answered in my answer to your third question (The protons fuse witht he electrons to form neutrons). The star's gravity does *not* increase at all as it changes state. An increase in gravity means an increase in mass and unless the star is in a binary system and is stealing matter from a companion star, it does not gain any mass.


"5. wat is a neutron star? totally made up of neutrons?" - MrOKL

Yup :)


"6. wat will happen if the neutron star collides with somethin(eg.earth)?"

I think that if the two objects fuse then a more massive neutron star would be made (A neutron star would be much smaller than the earth - smaller than Washington, D.C.). The new object would contract and a slightly larger neutron star would emerge. If the mass limit to become a black hole is surpassed, then the transformation to a black hole begins.


"7. wat will happen if the white dwarf collides with somethin(eg.earth)?" - MrOKL

I think that if the two objects fuse then a more massive white would be made (A white dwarf is about the same size as the earth). The new object would contract and a slightly larger white dwarf star would emerge. If the mass limit to become a neutron star is surpassed, then the transformation to a neutron star begins.


"8. does the gravity change from one state to another or does it suddenly grow large? (eg. slamming the door shut to close the door, or pushing a door to close it slowly)" - MrOKL

The gravity does not change at all at any time of the core's collapse.


"9. if the black hole forms by state to state, how long will it take? and how long does it take from one state to transform to the other?" - MrOKL

That is a great question (my favorite :-) and the answer is, I don't know. I never learned about pressure and such in physics like I should have, so I don't know what equations to use.


"10. does the black hole move? if so, randomly or in a particular manner(eg. earth's orbit around earth)?" - MrOKL

As far as I know, the black hole would move in exactly the same manner as it did when it was a star (actually, since it lost mass in its supernova its motion around the galaxy and/or companion star(s) might change a bit too).

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