Supernova Explosion

After the core explosion, the penetrating shock wave reaches the outer layers of the star, which are blown off into the interstellar medium. The shock wave breaks through the photosphere (not to be confused with the neutrinosphere), which leads to the final stage, observed as a supernova. In the soft outer stellar envelope, where the binding energy is small and processes like photodissociation of nuclei or neutrino loss are negligible, the shock proceeds without obstacles. The propagation time of the shock depends on the size of the stellar radius, nevertheless generally the order of magnitude is between several hours to days.

However, before the burst of electromagnetic waves can be recognized as supernova explosion, a prodigious neutrino burst from the core reaches us in advance, signaling the occurrence of a supernova and the birth of a neutron star.