Importantly, one type of supernova, the Type Ia, is indeed powered by nuclear energy. In fact, and ironically, all of the supernovae observed by Baade and Zwicky in the 1930s were of this type, not of the majority type currently thought to be powered ultimately by gravitation. In this case a pulsar is seen which rotates 30 times a second and emits a rotating beam of X-rays (like a lighthouse). Another dramatic supernova remnant is the Cygnus Loop. The set of small GIF images used to create the supernova inline animation is available. See also the X-ray binary and black hole inline animations.
The supernova that formed the Crab Nebula was so bright that astronomers could see it during the day. Other supernovae that were observed before the telescope was invented occurred in 393, 1006 ... The study of a supernova is more than just a study of any ordinary light show. Both the light and spectrum of color of a supernova can be used to make conclusions about the physics that occurs during and after supernova explosions. Understanding how a supernova explosion occurs and progresses is crucial to understanding why certain stars go boom. A supernova explosion can leave behind two bits of evidence for its passing: a pulsar and a supernova remnant. A pulsar is a spinning neutron star, about 1.4 times as massive as the Sun but with a diameter of only 20 kilometers.