The Crab Nebula, the result of a supernova noted by earth-bound chroniclers in 1054 AD, filled with mysterious filaments that are not only tremendously complex, but appear to have less mass than expelled in the original supernova and a higher speed than expected from a free explosion. The Crab Nebula spans about 10 light-years. In the nebula's very centre lies a pulsar: A neutron star as massive as the Sun but with only the size of a small town. The Crab Pulsar rotates about 30 times each second.