Supernova and planets. Computer artwork of a supernova (centre) exploding, an event which will devastate or destroy the two planets shown in the foreground (upper right and lower left). A supernova is the result of a massive star exhausting the hydrogen and helium that fuel its nuclear fires. It is the heat from these nuclear fusion processes that prevents the star collapsing under its own weight. As the core collapses, a rebounding shock wave blows off the outer layers of the star (red and yellow) at thousands of kilometres per second. A supernova may briefly outshine an entire galaxy.