How cataclysmic is a supernova explosion?
When a star becomes a supernova, its luminosity may increase by one hundred million times. A supernova can even become bright enough to be seen in daylight. The explosion is very sudden and occurs in a matter of days and gradually loses its brightness within a few months.
How frequency do supernovae occur?
The average frequency of a supernova in a galaxy like the Milky Way is about three super-novae per centaury. Three spectacular supernovas, recorded in our galaxy, occurred in 1054, 1573 and 1604.