Neutron star pulsar

Pulsars are rapidly rotating neutron stars that emit beams of radiation, sweeping across space like cosmic lighthouses.

About this subject

Pulsars are among the most fascinating objects in the universe: neutron stars that spin at extreme speeds, often hundreds of times per second. They form when massive stars (over 8 solar masses) collapse at the end of their lives, exploding as supernovae and leaving behind an ultra-dense core, with a mass comparable to the Sun's compressed into only about 20 kilometers in diameter.

What makes pulsars especially detectable is their radiation beam, emitting radio waves, X-rays, or gamma rays. Due to rapid rotation and a strong magnetic field, this beam sweeps across space like a lighthouse; when it points toward Earth, we detect a rhythmic pulse. The first pulsar was discovered in 1967 by Jocelyn Bell Burnell, a milestone in astrophysics that earned the Nobel Prize in Physics for her supervisors.

Pulsars are natural laboratories for testing general relativity. For example, the binary pulsar PSR B1913+16 (discovered by Hulse and Taylor) provided the first indirect detection of gravitational waves, showing that its orbit shrank exactly as predicted by Einstein. Moreover, millisecond pulsars, spinning hundreds of times per second, are the most precise clocks in the universe, used to study the interstellar medium and even attempt to detect low-frequency gravitational waves.

Although extreme, pulsars are relatively common: it is estimated that there are hundreds of millions just in the Milky Way. The most famous is the Crab Pulsar (PSR B0531+21), remnant of the 1054 supernova, which pulses about 30 times per second. Observing them requires sensitive radio, X-ray, or gamma-ray telescopes, and each new pulsar discovered expands our knowledge of matter physics under conditions impossible to recreate on Earth.

Frequently Asked Questions

What causes the regular pulses from a pulsar?

The pulses are caused by the rapid rotation of the neutron star. Its strong magnetic field concentrates radiation into narrow beams at the magnetic poles. As the star rotates, these beams sweep across space, and when they point toward Earth, we detect a pulse.

What is the difference between a neutron star and a pulsar?

Any neutron star that emits regular pulses of radiation is a pulsar. In other words: a pulsar is a neutron star oriented such that its radiation beam crosses Earth's line of sight, making it detectable as a cosmic lighthouse.

Can pulsars be used for space navigation?

Yes, there is the concept of pulsar navigation. Because pulsars emit extremely regular pulses, they can serve as cosmic beacons. Missions like NICER aboard the ISS have tested algorithms to determine a spacecraft's position using pulsar signals.