Crab Nebula pulsar. Coloured optical image of the core of the Crab Nebula (M1), taken by the Hubble Space Telescope. At the centre of the Crab lies a pulsar, a rapidly spinning neutron star which is the remnant of a supernova explosion observed in 1054 A.D. The pulsar is the star at lower centre; an unrelated foreground star is to its left. The pulsar has intense rotating gravitational and magnetic fields which shoot subatomic particles away from the centre of the nebula at half the speed of light. These particles collide with the nebula's gas to cause the bright bands of emission at centre and the more diffuse emission at top.