gollum123 writes, "NASA's Swift satellite has seen a giant flare explode from a nearby star. Our sun also flares when twisted magnetic field lines in the solar atmosphere suddenly snap — but this was on a far larger scale, perhaps 100 million times as strong. The energy released by the explosion on II Pegasi was equivalent to about 50 quintillion atomic bombs. If the Sun were ever to produce such an outburst, it would almost certainly cause a mass extinction on Earth. II Pegasi is a binary system 135 light-years from Earth in the constellation Pegasus. Its two stars are close, only a few stellar radii apart; as a result, tidal forces cause both stars to spin quickly, rotating in lockstep once in seven days compared to the Sun's 28-day rotation period. Fast rotation is thought to be conducive to strong stellar flares."