Neutron Degeneracy

[Soccerman06]

I thought once a massive star reached the point its life it core collapsed into Electron, Proton, then Neutron Degeneracy, and then it became a Neutron star and eventually a black hole, so at what point does Quark Degeneracy occur?

edit: Why am I up at 4:40am ???

 

[Biftheunderstudy]

The end stage of a star depends entirely on the mass of the initial star. If the star is less than 3 solar masses or so the star will form a red giant first then when the helium is all burned up the electron degeneracy keeps the star from collapsing further. The star that is left over after the red giant blows off its shell of hydrogen is called a blue dwarf. BTW degeneracy is caused by the pauli exclusion principle.

If the initial star is larger than that needed to make a blue dwarf, the fusion burning process will continue until iron is made, within days the core is converted to completely iron. Once iron is there the star is doomed since iron cannot be burned exothermally, the protons decay into neutrons, electrons and electron neutrinos. The shells on the outside start to fall in very rapidly since there is no more fusion in the core. When the shell hits the neutron core(held up by neutron degeneracy) it rebounds off the hard core and explodes aka supernova type II. Since neutrinos interact very weakly we can detect the burst when the protons decay in a supernova before seeing the explosion, indeed in 1987 such a neutrino event was detected shortly before supernova 1987a was detected.

If the initial mass is past another critical point neutron degeneracy is not able to hold up the core, it is at this point where a theoretical quark star would be found. This mass range would probably be very small since the next step is a black hole where no force is able to stop the collapse of the star to a point. The process involved is also VERY explosive so it would be kind of touch and go weather a star with the right mass woud stay together to make such an odd star. Also a quark star would be rediculously small and would be almost indistinguishable from a black hole from the distances which we view them.

 

[Soccerman06]

Well at mass does that happen, cause I know there are stars with 12Mo (solar mass). I know its all theoretical, but at what point is it that forces Quark Degeneracy?

oh btw thanks fo the copy and paste.

 

[Biftheunderstudy]

Heh, that was off the top of my head(don't have a textbook at home). You can tell cuz I wrote blue dwarf instead of the correct white dwarf.....
Turns out the upper mass limit for white dwarves and electron degeneracy is about 1.44 solar masses, thats after the star has evolved to that stage and I'm not too sure about the stars initial mass. After the 1.44 solar masses comes the neutron star until around 3 solar masses when the final collapse to the black hole occurs. A quark star would come somewhere between neutron and black hole, although it is still highly theoretical work.

Guy named Chandrasekhar figured all this out and did the calculations.

 

[Soccerman06]

You cant have a neutron star at a solar mass of only 3, it has to be much higher at 8-25 Mo. Its once the outter shell of the sun (everthing outside of the Convection Zone) or the core that has to have a mass of atleast 3Mo to create Neutron Degeneracy.

 

[Biftheunderstudy]

The core of the star has to be 3 solar masses is what I meant. Current models still can't make a star explode so it is still very much theory just how big a star has to be initially to make a white dwarf/neutron/black hole. As for quark stars there is a lot of conjecture whether they can be made from this process at all, one theory is that they are made from neutron stars that are very close to the upper limit then have mass acreted onto them slowly until the mass is just enough to make a quark star.