Pulsars are highly magnetized, rotating neutron stars that emit intense beams of electromagnetic radiation from their magnetic poles. As the star spins, these beams sweep through space like a lighthouse. If one of the beams crosses Earth, we detect it as a regular pulse of radio waves, X-rays, or gamma rays—hence the name pulsar.
Neutron stars, including pulsars, are the collapsed cores of massive stars that exploded in supernovae. They are incredibly dense—packing more mass than the Sun into a sphere only about 20 kilometers across. Their rotation rates can be astonishing: some pulsars spin hundreds of times per second.
Pulsars are extremely stable and precise, making them valuable tools in astrophysics. Scientists use them to test general relativity, detect gravitational waves (through pulsar timing arrays), and even explore the interstellar medium. Some pulsars in binary systems, especially millisecond pulsars, are spun up by accreting matter from a companion star and serve as cosmic clocks with unmatched precision.