What is a pulsar? A pulsar is a rapidly spinning neutron star. So, what’s a neutron star? A neutron star is the small, incredibly dense remnant of a much more massive star. Neutron stars are so dense that if you could scoop up a teaspoon from off the surface of the star, it would weigh as much as Mount Everest. A neutron star of about 15 miles (24 km) across would contain more matter than our sun. So why are some neutron stars – the ones we see as pulsars – pulsing? How a pulsar is born? To lear