A pulsar is a highly magnetized, rotating neutron star that emits beams of electromagnetic radiation out of its magnetic poles. Neutron stars are incredibly dense celestial objects that form when a massive star undergoes a supernova explosion and collapses under its own gravity. Pulsars are among the most exotic and extreme objects in the universe.
When a massive star explodes, its core collapses into a neutron star, which is only about 20 kilometers (12 miles) in diameter but contains a mass greater than that of the Sun. The collapse causes the star to spin rapidly due to the conservation of angular momentum. Pulsars can rotate at incredible speeds, ranging from several rotations per second to hundreds of rotations per second.
As the pulsar spins, it generates powerful magnetic fields that are thousands to billions of times stronger than Earth's magnetic field. These magnetic fields are not symmetrically aligned with the rotational axis, resulting in the emission of narrow beams of radiation from the magnetic poles. These beams of radiation can be observed as periodic pulses of electromagnetic waves, hence the name "pulsar."
If the beams of radiation from a pulsar sweep past the Earth, like a cosmic lighthouse, astronomers detect regular pulses of radio waves, X-rays, or gamma rays. The rotation of the pulsar causes these pulses to be extremely precise and periodic. Pulsars are known for their exceptional stability, and their pulses can be used as highly accurate cosmic clocks for scientific research.
Pulsars are predominantly observed in the radio wavelength, but they can also emit radiation across the entire electromagnetic spectrum, from radio waves to gamma rays. They can be detected by radio telescopes, X-ray telescopes, and gamma-ray telescopes.
Studying pulsars provides valuable insights into various areas of astrophysics, including the physics of extreme conditions, the behavior of matter under extreme densities and magnetic fields, general relativity, and the study of cosmic magnetic fields. Pulsars are also used to indirectly detect other astronomical phenomena, such as gravitational waves and extrasolar planets.