4 ms·
> They are unable to decay into protons plus electrons because there isn't enough "room" for the two particles to exist in the space formerly taken up by one pa
by swombat 11y ago
> They are unable to decay into protons plus electrons because there isn't enough "room" for the two particles to exist in the space formerly taken up by one particle. See: Electron degeneracy pressure.
Just being pedantic here but in a neutron star, it's neutron degeneracy pressure that's at play. Electron degeneracy pressure keeps a white (and later brown) dwarf from collapsing further, but if there's enough mass it is overcome and the next thing that kicks in is neutron degeneracy pressure, which for whatever reason is a lot stronger, and holds up another solar mass or two before it passes the limit where collapsing into a black hole is inevitable.
The principles for both types of degeneracy are similar (it's the Pauli exclusion principle at work basically) but the particles are different.
- piannucci 11y agoGP is correct-- the neutron degeneracy pressure prevents the stellar remnant from getting any smaller, but it is the electron degeneracy pressure which makes beta decay energetically unfavorable. In order to be produced by neutron beta decay, an electron must enter a valid state. Pauli exclusion (electrons are fermions) requires the electron to enter a state at least as energetic as the electron Fermi level, which due to the neutron star's gravity is comparable to the rest mass of the electron. Neutron decay is energetically favorable, but not that favorable. The reverse process accelerates and equilibrium is reached.