What mechanism initially provides resistance against gravitational compression in a massive star before core collapse?

Answer

Electron degeneracy pressure

The structure of the star is normally held up by electron degeneracy pressure, a quantum mechanical force stating that electrons cannot occupy the same quantum state, providing stiff resistance to compression.

What mechanism initially provides resistance against gravitational compression in a massive star before core collapse?
starsupernovaexplosioncore collapseImplosion