What is a pulsar?
A pulsar is a rapidly spinning neutron star that sends beams of radio waves or other radiation from its magnetic poles. As it spins, the beams sweep past Earth like a lighthouse, creating regular pulses.
Pulsars form when massive stars explode as supernovas and their cores collapse into incredibly dense neutron stars. These stars spin very fast, some hundreds of times per second, and have extremely strong magnetic fields. Radiation streams out from the magnetic poles, which are often tilted from the spin axis.
The first pulsar was discovered in 1967 by Jocelyn Bell Burnell, a graduate student at the University of Cambridge, who noticed a strange, regular signal in radio data. Because it was so regular, the team jokingly nicknamed it LGM-1, for Little Green Men, before realizing it had a natural cause.
Cosmic clocks
Pulsars are some of the most precise clocks in the universe. Astronomers use groups of them, called pulsar timing arrays, to detect tiny ripples in space-time. In 2023, these projects reported evidence of a background of low-frequency gravitational waves.
Did You Know?
The Crab Pulsar, in the remains of a supernova seen in 1054, spins about 30 times every second.