A neutron star is a rotating, superdense, dead star. A pulsar is a type of neutron star that must be both magnetized and moving very fast, because it spins its magnetic field fast enough to produce a beam of electromagnetic radiation. Astrophysicist Andrea Lommen explains a research study of the binary system known a PSR 1913+16, where a neutron star and a pulsar orbit each other. This study yielded a result that only Einstein would have found unsurprising: gravitational waves must exist!
