Answer to Question #202921 in Astronomy | Astrophysics for Prachi

Question

Explain the concept of degeneracy pressure. What role does it play in the evolution of a star after its death?

Answer 1

According to www.dictionary.com, the degeneracy pressure is exerted by dense material consisting of fermions. Pauli exclusion principle states that no two fermions can be in the same quantum state, so when a large amount of fermions is situated in a small space, their momentum differs a lot, and a higher fraction of fermions with large momenta exert the pressure.

According to quantummechanics.ucsd.edu, the pressure exerted by fermions prevents cooling stars from collapse. White dwarfs are held up by electrons and neutron stars are held up by neutrons. When the white dwarf exhausts its nuclear fuel, it begins to cool and to shrink, and its radius decreases and eventually is stopped because pressure from the electrons grows faster than the pressure of gravity.

In neutron stars after the absorption of the electrons into the nuclei the collapse is stopped when the pressure of neutrons stops balances the pressure of gravity.

Therefore, the degeneracy pressure is important because it prevents the stars with small and moderate masses from collapse to a extremely dense object such as a black hole.