What do we call an exploding star?

An exploding star is referred to as a supernova. This term specifically describes the astronomical event that occurs when a star exhausts its nuclear fuel and undergoes a dramatic explosion, resulting in a significant increase in brightness followed by a gradual fading. Supernovae play a fundamental role in the universe as they are responsible for dispersing elements into space, enriching the interstellar medium and allowing for the formation of new stars and planets.

Other options represent different stages or types of stars rather than the explosion itself. A red supergiant is a phase in the evolution of certain massive stars, while a nova is a different phenomenon involving a white dwarf in a binary system that explodes on the surface due to nuclear fusion. A pulsar, on the other hand, is a highly magnetized rotating neutron star that emits beams of electromagnetic radiation. Each of these terms relates to stellar phenomena, but only a supernova refers specifically to the explosive end of a star's life cycle.