Pulsars

Pulsars are rapidly rotating neutron stars that emit beams of electromagnetic radiation from their magnetic poles. As the star rotates, these beams sweep across space like a cosmic lighthouse. When the beam points toward Earth, we detect a pulse of radiation. Pulsars are the collapsed cores of massive stars that exploded as supernovae, compressed to the size of a city but with more mass than the Sun.

The fastest pulsars, called millisecond pulsars, rotate hundreds of times per second. These are incredibly precise cosmic clocks, with timing accuracy better than atomic clocks. Scientists use pulsars to test Einstein's theory of general relativity and to search for gravitational waves. The precision of pulsar timing makes them valuable tools for fundamental physics.