"Great Guest Star"

On May 1, 1006, a bright new star appeared in the constellation Lupus. Within a few days of its discovery, the star brightened tremendously, becoming probably the brightest star ever observed from Earth. Though at the time, astronomers were confused as to the real nature of the star, the event is now recognized as a supernova, and this week marks its 1000-year anniversary. Here, a short essay from the NYTimes.