[lanstin]

To quote Wikipedia: “Lepton flavor is only approximately conserved, and is notably not conserved in neutrino oscillation.[6] However, total lepton number is still conserved in the Standard Model.“

The beta decay gives rise to e.g. a positron and a neutrino (or an electron and an anti-neutrino).

[floxy]

What is going on in neutron stars? The layman's answer is that the electrons get squeezed into the protons due to the extreme gravity, leaving only neutrons. But I suppose (?) there needs to be a anti-neutrino or similar that comes along to "complete" the reaction?

Edit: I guess it is inverse beta decay:

https://en.wikipedia.org/wiki/Inverse_beta_decay#Electron_in...