supernova would have been on the day the supernova was first visible on Earth. 
    According to the Chinese astronomers, the “guest star” could be seen in broad daylight for three weeks, was bright in the night sky for six months, and disappeared (there being no telescopes at the time) after about 21 months. This pattern of brightness followed by decline is consistent with the modern understanding of supernova behavior.
    After the invention of the tele- scope, the English amateur astrono- mer John Bevis rediscovered the Crab supernova as a nebula in 1731, as did the great French astronomer Charles Messier, independently in 1758. It was this finding that prompted Messier, who was