Astronomers have lost a star. This is not carelessness, but the possible discovery of a rare stellar event in the Andromeda galaxy. A red supergiant star got brighter and brighter,as if it was about to go supernova – and then dramatically dimmed, disappearing from view from most telescopes. Researchers believe they may have caught a rare failed supernova. Basically, it is believed that some stars are too big not to fail. There might be a mass range where a star has all that it needs to go supernova. But when the collapse happens, its core rapidly becomes a black hole, without a devastating exp…