Which astronomical event is characterized as a powerful explosion of a star?

A supernova is indeed characterized as a powerful explosion of a star. This event occurs at the end of a star's life cycle, particularly for massive stars, which undergo a dramatic collapse under their own gravity after exhausting their nuclear fuel. When this happens, the outer layers of the star are expelled violently into space, releasing an immense amount of energy and light, which can outshine entire galaxies for a short period. This explosion also enriches the surrounding interstellar medium with heavy elements, contributing to the formation of new stars and planets. The energy emitted during a supernova can be observed across vast distances, making them one of the most spectacular phenomena in the universe.

In contrast, a nova refers to a lesser explosion on the surface of a white dwarf star caused by the accumulation of material from a companion star. A black hole is the remnants of a massive star that has undergone gravitational collapse, not an explosion. A neutron star is the dense core left behind after a supernova, composed mainly of neutrons. Therefore, the supernova distinctly represents the explosive event that signifies a star's dramatic end.