What phenomenon occurs in stars that allows them to collapse and explode as supernovae?

The phenomenon that allows stars to collapse and explode as supernovae is gravitational collapse. When a massive star exhausts its nuclear fuel, it can no longer counteract the force of gravity with the outward pressure generated by nuclear fusion. As a result, the core of the star collapses under its own gravitational pull. This process leads to an increase in temperature and density, eventually resulting in conditions that can trigger a supernova explosion.

During the final stages of a star's life, as the core contracts, it may form a neutron star or black hole, depending on its mass. The outer layers of the star are violently expelled during the supernova explosion, which enriches the surrounding interstellar medium with heavy elements created during the star's lifetime. This plays a crucial role in the ongoing cycle of star formation and the distribution of elements in the universe.

In contrast, phenomena such as nuclear decay and hydrostatic equilibrium do not directly account for the explosive end of a massive star's life cycle. Nuclear decay refers to the process by which unstable atomic nuclei lose energy by emitting radiation, while hydrostatic equilibrium describes the balance between gravitational forces and pressure within a star. Photon pressure, another important concept, relates to the outward pressure from photons generated in nuclear fusion