What is the term used for a star explosion?

The term that refers to a star explosion is "supernova." This is a powerful and luminous phase of a star's life cycle that occurs when a star exhausts its nuclear fuel and can no longer support itself against gravitational collapse. During this explosive event, the outer layers of the star are expelled into space, often outshining entire galaxies for a brief period and leaving behind a core that can become a neutron star or black hole depending on the mass of the original star.

The other terms represent different astronomical phenomena: a black hole is a region in space where gravity is so strong that nothing, not even light, can escape from it; a neutron star is the remnants of a supernova, composed almost entirely of neutrons, and is extremely dense; a red giant, on the other hand, is a phase in a star's evolution before it explodes as a supernova, characterized by the star's expansion and cooling of its outer layers.