Crab Pulsar neutron star. Animation of the location in the night sky and the properties of the Crab Pulsar neutron star (PSR B0531+21), 7180 light years from Earth in the constellation of Taurus. The Crab Pulsar is a neutron star, 0.0000143 times the width of the Sun (just under 20 kilometres across) and 1.4 times the Sun's mass. The Crab Pulsar formed in 1054 and is the remnant left behind by the supernova SN 1054 (an explosion of a massive star) that also formed the Crab Nebula. It is an extremely dense object, spinning rapidly and emitting beams of radiation 30 times a second. The Crab Pulsar's luminosity is unknown. It has an atmospheric temperature of 1.6 million Kelvin. Its spectrum has no lines of note and has a featureless optical region.