In the year 1181 AD, a new bright point of light as luminous as the planet Saturn appeared to Chinese and Japanese skygazers for a little more than six months before disappearing. Hundreds of years later, researchers believe they have finally found the source of this mysterious appearance. The event, like the famous Crab Nebula-forming stellar explosion of 1054, is one of just a handful of bright nearby flashes noted in historical records, but unlike the Crab Nebula, the 1181 spectacle was tricky to pin down. The historical record leaves a few clues that have been useful to modern astronomers....