Pulsars are neutron stars, which are themselves the collapsed cores of supernovae.
According to a new theory, the simplest explanation for their speed is a subatomic drama in the collapsing core that culminates in a violent, and slightly uneven, blast of neutrinos. Most pulsars are between 20 and 30 kilometres in diameter, with intense magnetic fields and rapid spins. In extreme cases, pulsars can spin more than 100 times a second. From Earth, they appear to pulsate because the beams of radio waves they emit from their poles sweep past the Earth with every revolution. Since the discovery of the first pulsar in 1967, astronomers have struggled to explain why they travel so fast.