•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