A supernova explosion is usually associated with the formation of black holes and neutron stars. To understand what explodes and what collapses, we need to talk about what happens during a supernova explosion. Young stars are hydrogen, and the nuclear reaction converts hydrogen to helium with energy left over. When most of the hydrogen has been converted to helium, a new nuclear reaction begins that converts the helium to carbon, with the left over energy released as radiation. This process continues converting the carbon to oxygen to silicon to iron.
Nuclear fusion stops at iron.
The outer layers of hydrogen, helium, carbon, and silicon are still burning around the iron core, building it up. Eventually, the massive iron core succumbs to gravity and it collapses to form a neutron star. The outer layers of the star fall in and bounce off the neutron core which creates a shock wave that blows the outer layer outward. This is the supernova explosion. This Web page was written and is maintained by Chris Miller .