Stars don't last forever. Occasionally, a star bigger than our Sun will end its life in a huge explosion, called a supernova.

This explosion happens because the center, or core, of the star collapses in less than a second. The outer layers of the star are blown off in the explosion, leaving a contracting core of the star after the supernova. The shock waves and material that fly out from the supernova can cause the formation of new stars. There are many beautiful images of supernova remnants, the expanding shell of gas made up of the outer layers of the original star.

Supernovae last one or two years, and can shine brighter than a whole galaxy for this time. What happens to the star after the supernova depends on how big it was to begin with. If the star was only a few times bigger than the Sun, the core will shrink into a tiny neutron star only a few miles across. If the star was much bigger than the Sun, the core will shrink down to a black hole.