What are pulsars and why do they pulse?

Pulsars are highly magnetized, rotating neutron stars that emit beams of electromagnetic radiation.

Pulsars are formed when a massive star undergoes a supernova explosion and its core collapses into a neutron star. Neutron stars are incredibly dense, with a mass greater than that of the sun but compressed into a sphere only a few kilometers in diameter. Pulsars are also highly magnetized, with magnetic fields trillions of times stronger than Earth's.

As pulsars rotate, they emit beams of electromagnetic radiation from their magnetic poles. These beams are not emitted uniformly, but rather in a narrow cone that sweeps across space as the pulsar rotates. If Earth happens to be in the path of one of these beams, we observe a pulse of radiation each time the beam sweeps past us.

The rate at which a pulsar emits pulses is incredibly regular, with some pulsars emitting hundreds of pulses per second. This regularity is due to the incredibly stable rotation of the neutron star, which is maintained by the conservation of angular momentum. Any changes in the rotation rate of a pulsar can be detected as a change in the timing of its pulses, making pulsars valuable tools for studying the properties of neutron stars and the effects of gravity.