Supernova

A supernova is the massive explosion of a star, and is one of the most violent events in the Universe. There are two types of supernovae. A Type I supernova happens when a dead star called a white dwarf accretes so much matter from a companion star that it becomes unstable and explodes. A Type II supernova occurs when a high-mass star runs out of thermonuclear fuel. In this case, the star's core collapses and becomes tremendously hard and rigid. The collapsing outer layers of the star bounce off the core and are flung outward with a burst of energy that can rival the output of an entire galaxy.