Core-Collapse Supernovae
Marking the death of a massive star (greater than 8 times the mass of the sun) and the birth of a neutron star or black hole, core-collapse supernovae are among the most spectacular of cosmic explosions. The collapse of the core of a massive star proceeds until super-nuclear densities, larger than the densities inside atomic nuclei, are reached. The inner core becomes incompressible under these extremes, bounces, and, acting like a piston, launches a shock wave into the outer stellar core. This shock wave will ultimately propagate through the stellar layers beyond the core and disrupt the star in a SN explosion.
However, the shock stalls in the outer core, losing energy as it plows through it, and exactly how the shock is revived is the central question in supernova theory. After core bounce, about 1046 Joules of energy in the form of neutrinos and antineutrinos is released from the newly formed proto-neutron star at the center of the explosion. The observed kinetic energy of the supernova explosion is roughly 1044 Joules erg. Past simulations demonstrate that energy in the form of neutrinos emerging from the PNS can be deposited behind the shock and may revive it. This is the so-called Wilson delayed-shock mechanism and is central to our modern understanding of CCSN. However, while a prodigious amount of neutrino energy emerges from the PNS, the neutrinos are weakly coupled to the material directly below the shock.
The entropy inside a core-collapse supernova is shown, with greater entropy represented by “warmer” hues. At center is a volume rendering of the developing explosion above the newly formed neutron star (based on a simulation with the CHIMERA); side images of orthogonal slices through the star reveal additional detail. The movie starts 100 milliseconds after the formation of the neutron star, depicts the shockwave’s bounce and follows astrophysical events up to 432 milliseconds after the bounce. Created by J.A. Harris (ORNL)