The Crab Nebula is a Type II supernova remnant located 6,300 light years from Earth in the constellation Taurus.  The nebula diameter is 11 light years, and it is expanding at the rate of 1,500 kilometers per second.  The supernova explosion occurred in 1054 and was documented by both Chinese and Arab astronomers.  At the heart of the nebula is the Crab Pulsar, a neutron star with a mass of approximately 1.4 to 2.0 solar masses.  The Crab Pulsar is approximately the diameter of the Earth and rotates at 30.2 times per second.