Electron Capture and Neutronization
The formation of a neutron star results from a process called electron capture,
which is a form of beta decay that we mentioned in conjunction with
stellar energy production in Chapter 18. The process is also called
neutronization, because its effect is to destroy protons and electrons and create
neutrons. The basic reaction is
e - + p + --> n + electron neutrino
Speaking loosely, the negatively charged electron and positively charged proton are crushed
together to form a neutron and a neutrino, neither of which carry electrical charge.
This reaction is slow under normal conditions, but very fast in the high density and temperature
of a core collapse.
The neutrinos escape, leaving behind the neutrons. Because neutrons carry no charge, there is no
electrical repulsion as in normal matter and the core can collapse to very high density once it
has become mostly neutrons.