As a rule, astronomers believe that stars have to explode in a supernova before they collapse into black holes. That violent death is always the cue, right? Not necessarily. Researchers have spotted a massive star 22 million light years away, N6946-BH1, that appears to have skipped the supernova step entirely -- it brightened slightly and just disappeared. Checks have ruled out a dimmed star or dust. And this probably isn't a one-off incident, either. Ohio State University's Christopher Kochanek tells NASA that 10 to 30 percent of massive stars might die in failed supernovae.