Supernova

Chandra X-ray photograph shows CAssiopeia A

     Once in awhile, you would hear people talking about supernova and for most people they would not know what is a supernova. So what is exactly a supernova?
   A supernova is a stellar explosion that is more energetic than a nova. Supernovae are extremely luminous and cause a burst of radiation that often briefly outshines an entire galaxy, before fading from view over several weeks or months. This is one of the reasons why many people would think supernova is something powerful or something really extreme. Supernovae can radiate more energy than our sun will in its entire lifetime. They are also the primary source of heavy elements in the universe.
     On average, a supernova will occur about once every 50 years in a galaxy the size of the Milky Way. Put another way, a star explodes every second or so somewhere in the universe. According to Helium and Lead Observatory, there are two ways that a star can transform into a supernova. One way is that a star accumulates matter from a nearby neighbor until a runaway nuclear reaction ignites. The other way is that a star runs out of nuclear fuel and collapses under its own gravity.
     Some people might wondering how a star can die? Well, a star dies depends in part on its mass. Our sun, for example, does not have enough mass to explode as a supernova. Many scientists predicted the sun will run out of it nuclear fuel in a couple billion years, it will swell into a red giant that will likely vaporize our world before gradually cooling into a white dwarf. That is not a very good news for us.


http://www.space.com/6638-supernova.html

http://www.snolab.ca/halo/faq.html