Question: What is a Supernova

Heather Campbell answered on 11 Nov 2014:

Supernovae are the explosions of stars at the end of their lives. (not all stars will explode as supernovae it depends on how much mass they have)

Stars burn hydrogen in their cores to power them. Large stars (5-8 times the size of our sun) can also burn heavier elements, helium, carbon ect. as the pressure is much great due to the larger mass. This goes all the way though until there is iron in the core of the star. The there is nothing left to burn and so nothing to stop the gravitational pull. The star collapses which increased the pressure and energy by a huge amount and the star explodes. This is called a core-collapse supernovae.

The other type is from two stars (a binary system). Where one of the stars in an old very dense star called a white dwarf, which is about half the mass of the sun, in about the size of the earth. a square about a sugar cube size would weight about the same as a rhino! This steels material from a companion star (or they might collide with each other) until it reaches a mass where it can no longer over power the gravity, the pressure gets so high they ignite and a supernovae explosion occurs. This is called a Type Ia supernovae.