Supernovas are exploding stars. The last nearby supernova seen with the naked eye occurred in the Large Magellanic Cloud, 160,000 LY away, in 1987. But a simple nova, while it represents a dying star, is not an exploding star. Novae are found in binary systems, where one star is still on the main sequence and the other has become a white dwarf. The white dwarf’s gravity is sufficient to pull gas off its companion, but the stolen gas doesn’t go straight onto the dwarf; instead, it spirals around, forming an accretion disc that surrounds the dying star. At regular intervals of time, this disc gas touches down on the surface of the white dwarf and ignites, creating a flare-up in the star. The white dwarf brightens considerably for a while, then dims down again – until more gas has piled up in the disc and the cycle repeats itself. This can go on for years and years. However, if the white dwarf pulls too much material down and its end mass becomes great enough, it can also explode and become a supernova!