What is now the Crab Nebula was formed by the second brightest ever supernova explosion in recorded history. It was noted in the records of four cultures, most notably the Chinese but not the West, though it was just 12 years before the Norman conquest of England in 1066. The supernova lit up in 1054 with an estimated peak brightness about ten times that of Venus, visible in the daytime and remaining visible in the night sky for two years.
The remnant neutron star for SN1054 it has been observe with both optical and radio telescopes. The Crab Nebula neutron star is little under 20 miles in diameter and with 30 rpm rotation speed emits about 75,000 times as much energy as the sun. This creates both the pulsar effect and in the very center of the nebula inflicts considerable disturbance with changes observed to occur in only days.
By now the gases blown off by the supernova have reached a diameter of about 11 light years, and they still expand at about 0.5% the speed of light.
The wispy nature of the Crab Nebula is due to electromagnetic radiation emitted by electrons that do not move on straight paths in these expanding gases. A very strong magnetic field from the rotating neutron star forces electrons to follow curved paths, and a fundamental property of electromagnetics is that charge moving along curved paths emits what is called synchrotron radiation.
Large image of Crab Nebula