Okay making this joke prompted me to re-read the wikipedia page, and there's something new to me:
The initial temperature of a neutron star is ~100 BILLION kelvin. It rapidly cools down with the energy going into a preposterous outflux of neutrinos. A lot of the energy of a released by a supernova is those neutrinos interacting with and heating the surrounding gas.
Woah!
@Felthry see followup post; I meant neutrons :/
@starkatt oh, that makes more sense, okay