What process converts protons and electrons into neutrons and neutrinos during core implosion?

Electron capture

As the iron core collapses under overwhelming gravity, its density rapidly increases. When the mass surpasses the Chandrasekhar limit, the collapse accelerates dramatically. During this phase, the extreme compression forces electrons and protons to merge, a process chemically represented as $ ext{p} + ext{e}^- ightarrow ext{n} + u_{ ext{e}}$. This reaction, known as electron capture, has two profound consequences: it creates massive amounts of neutrons, contributing to the formation of the neutron star, and it releases a flood of electron neutrinos ($ u_{ ext{e}}$). Crucially, by consuming the free electrons, this process removes the very particles that provided the primary outward thermal and degeneracy pressure necessary to support the star against gravity, thus hastening the core's implosion and contributing to the overall instability.