Although centuries ago astronomers thought that a supernova was a new star appearing for the first time in the heavens, today we know that it is:

a violently exploding star that releases light energy whose intensity can illuminate a whole galaxy.

Explanation:

A Supernova is a violent star explosion that causes the release of light that expands so many times and that is capable of illuminating a galaxy. It marks the end of a star and also results in the release of gamma rays, radio waves, x-rays, and heavy elements. Unlike a nova, a supernova destroys the star where it occurs.

A supernova is classified into Type I and Type II. Type I supernova produces three times more brightness than Type II and it occurs as a white dwarf absorbs hot gas from an associate star. The Type II supernova marks the end of the star. It lacks the ability to produce nuclear energy at its core and results in the collapse of the star.