The Bad Astronomer writes: "What's the nearest star to Earth that can explode as a supernova? Spica, at 260 light years away, is the nearest massive star that can explode, but IK Pegasi — a Sirius-like binary composed of a normal star and a white dwarf — will also one day blow. At a distance of 150 light years it's truly the closest supernova candidate. Happily, that's too far away to damage the Earth when it goes off — and it won't explode for millions of years at least, by which time it'll be even farther away. Either way, we're safe... for now."