•Imagine
compressing a star slightly (without
removing energy)
–Pressure goes up (trying to make star
expand)
–Gravity also goes up (trying to make
star collapse)
•Does
pressure go up faster than gravity?
–If Yes: star is stable – it bounces back
to original size
–If No: star is unstable – gravity
makes it collapses
•
•Ordinary gas: P does go up fast –
stable
•Non-relativistic degenerate gas: P does go up fast
– stable
•Relativistic degenerate gas: P does not go up fast –
unstable
–
–Relativistic: Mean are the electrons moving at
close to the speed of light
–
–Non-relativistic
degenerate gas: increasing r means not only more electrons, but faster electrons, which raises
pressure a lot.
–Relativistic
degenerate gas: increasing r can’t increase electron velocity
(they are
already going close to speed of light) so pressure doesn’t go up as much