Hydrostatic Equilibrium

 
A. Gravitational forces that tend to collapse the star are opposed by pressure derived from the  heat of fusion in the core region of the star.
B. As fusion fuel is reduced, the pressure generated is reduced, allowing gravity to compress the core further. 
C. Compression of the star generates heat that can increase the rate of fusion, thus reacquiring equilibrium. 
 
 
 
 
 
 Electron Degeneracy