Pulsars are formed when a massive star, at least 8 times the mass of our Sun, collapses under its gravity at the end of its life. The outer layers of the star explode in a supernova while the inner core collapses to form an incredibly dense neutron star. If the neutron star's magnetic field is strong and its rotation speed is rapid, it creates beams of electromagnetic radiation that sweep through space. These beams can produce a pulsing effect when received on Earth.