# Forming a Neutron Star: inverse $\beta^-$ decay or electron capture?

There are three different kinds of beta decays:

• $$\beta^-$$: n $$\rightarrow$$ p + e$$^-$$ + $$\overline{\nu}_{e^-}$$
• $$\beta^+$$: p $$\rightarrow$$ n + e$$^+$$ + $$\nu_{e}$$
• electron capture: p + e$$^-$$ $$\rightarrow$$ n + $$\nu_{e}$$

When the pressure in the core of a star becomes high enough, it is energetically favorable for electrons to fuse together with protons to form neutrons. A neutron star is born.

Is this fusion an inverse beta$$^-$$ decay or an electron capture? If the former: where does the necessary anti-neutrino come from? If the latter: as there are only two bodies involved, the energies should be sharp, is this observed or theoretically assured?

• I am nut sure I understand the question well. Are you asking if the electron capture under colossal compression was observed in laboratory? And by "theoretically assured" you mean whether theory clearly shows that it will inevitably happen? – mpv Jan 11 at 15:09
• – mpv Jan 17 at 15:23