A supernova is known as the bright flash caused by the exploding death of a large star. When a large star finally burns up all its hydrogen, it collapses and explodes in a powerful, bright burst. It releases a burst of energy called neutrinos that we can detect here on earth.
There are actually 2 types of supernovas. One is the explosion after the core collapse of a massive star decribed above. The other is the thermonuclear explosion of a growing white dwarf star.
In 1604 Johannes Kepler, a famous astronomer, watched a bright new star that had suddenly appeared in the night sky and stayed bright for almost a full year before fading away. This was the first recorded sighting of a supernova and is pictured in the Hubble photograph above.
Only six supernovas have been observed in our Milky Way in the last 1000 years.