core-collapse supernova

The core collapse of sufficiently massive stars may not be halted. Degeneracy pressure and repulsive neutron-neutron interactions can only support a neutron star whose mass does not exceed the Tolman-Oppenheimer-Volkoff limit of very roughly 4 solar masses. Above this limit, the core collapses to directly form a black hole, perhaps producing a (still theoretical) hypernova explosion. In the proposed hypernova mechanism (known as a collapsar) two extremely energetic jets of plasma are emitted from the star's rotational poles at nearly light speed. These jets emit intense gamma rays, and are one of many candidate explanations for gamma ray bursts.