Description This is an illustration of a Pulsar named 4U 0142+61Pulsars are a class of supernova remnants, called neutron stars, which are incredibly dense. They have masses about 1.4 times that of the sun squeezed into bodies only 10 miles wide. The pulsar named 4U 0142+61, is 13,000 light-years away in the constellation Cassiopeia. It was once a large, bright star with a mass between 10 and 20 times that of our sun. The star probably survived for about 10 million years, until it collapsed under its own weight about 100,000 years ago and blasted apart in a supernova explosion.