Description: The crab nebula is the visible cloud of expanding gas from a supernova witnessed by Chinese astronomers in 1054 AD. Chinese astronomers recorded that this exploding star was bright enough to be seen in the daytime! Material from that explosion is still expanding. M1 is about 4 x 6 arc minutes in size and is fairly bright at magnitude 8.4 though size is slowly increasing and therefore surface brightness decreasing over time.