A pulsar is a rotating neutron star with a strong magnetic field that emits beams of radiation from its magnetic poles. As the star rotates, the beams sweep across space, and observers see a highly regular pulse each time one points at them.

Why do pulsars spin so fast?

Conservation of angular momentum. A stellar core the size of Earth collapses to about 22 km across, so its rotation rate multiplies by tens of thousands. The fastest known pulsar spins 716 times per second.

Who discovered the first pulsar?

Jocelyn Bell Burnell detected it in 1967 while a graduate student at Cambridge. The signal repeated every 1.337 seconds and was initially nicknamed LGM-1, for "little green men", before a natural origin was established.

Are pulsars accurate clocks?

Extremely. The most stable millisecond pulsars rival atomic clocks over long timescales, which is why networks of them are used as galaxy-scale detectors for low-frequency gravitational waves.

Pulsarとは何か？

A pulsar is a rapidly rotating, strongly magnetised neutron star that fires beams of radiation from its magnetic poles. Because those poles are usually tilted away from the rotation axis, the beams sweep through space like a lighthouse — and if one crosses Earth, we see a pulse of astonishing regularity.

The spin is inherited. When a stellar core collapses from something the size of Earth to a ball 22 kilometres across, conservation of angular momentum spins it up by a factor of tens of thousands, exactly as a skater pulls in their arms. Known pulsars range from a few seconds per rotation down to PSR J1748-2446ad, which turns 716 times every second — its equator is moving at a quarter the speed of light.

Jocelyn Bell Burnell found the first one in 1967: a signal repeating every 1.337 seconds, so precise that it was half-jokingly catalogued as LGM-1, for "little green men". The natural explanation turned out to be stranger than the artificial one. The intense magnetic field, up to a trillion times Earth's, rips charged particles off the surface and accelerates them along field lines, producing tightly collimated beams from radio through gamma rays.

That regularity makes pulsars instruments. The fastest millisecond pulsars rival atomic clocks in long-term stability, and by watching an array of them across the sky for tiny correlated timing shifts, astronomers detected the gravitational-wave background from merging supermassive black holes in 2023. Pulsar timing also gave the first confirmed exoplanets, in 1992, and the first indirect proof that gravitational waves exist at all.