What is a supernova?

A supernova is a vast explosion in which an entire star is destroyed. After the explosion, extremely bright light is emittedfor several days. Supernovas are a billion times brighter than our Sun. Sometimes, a supernova explosion can go on for weeks or even months. So far, supernovas have only been seen in distant galaxies. The last supernova noted to take place in the Milky Way (our galaxy) was in 1604. It has been identified at the time by the famous astronomer Johannes Kepler.Note: The brightest supernova to be recorded so far was dubbed the 1993J and it occurred in the galaxy M81. It was seen on March 26th, 1993 (but it obviosuly happened a long time before that, since it was really far away)