In lower mass cores the collapse is stopped and the newly formed neutron core has an initial temperature of about 100 billion kelvin, 6000 times the temperature of the sun's core. At this temperature, neutrino-antineutrino pairs of all flavours are efficiently formed by thermal emission. These thermal neutrinos are several times more abundant than the electron-capture neutrinos. About 1046 joules, approximately 10% of the star's rest mass, is converted into a ten-second burst of neutrinos which is the main output of the event. The suddenly halted core collapse rebounds and produces a shock wave that stalls within milliseconds in the outer core as energy is lost through the dissociation of heavy elements. A process that is is necessary to allow the outer layers of the core to reabsorb around 1044 joules (1 foe) from the neutrino pulse, producing the visible brightness, although there are also other theories on how to power the explosion.