Beacons of X-ray Light

This animation shows a neutron star -- the core of a star that exploded in a massive supernova. This particular neutron star is known as a pulsar because it sends out rotating beams of X-rays that sweep past Earth like lighthouse beacons. X-ray telescopes like NASA’s Nuclear Spectroscopic Telescope Array, or NuSTAR, pick up these beams, registering them as pulses of X-ray light. What causes a pulsar to pulse? In the case of “accreting pulsars,“ the process is set in motion when matter from a companion sta