A supernova is a vast explosion in
which an entire star is destroyed. After the
explosion, extremely bright light is emitted
for several days. Supernovas appear a billion
times brighter than the Sun. Sometimes, a
supernova explosion can go on for weeks
or even months. Supernovas mostly occur in
distant galaxies. The last supernova to take
place in the Milky Way occurred in 1604. It
was observed by the famous astronomer
Johannes Kepler. The brightest supernova to
be recorded so far is 1993J in the galaxy M81.
It was seen on 26 March 1993. But because
the stars are so far away, we may see a
supernova explosion long after it takes place