Pulsar

A pulsar is composed of a fast rotating neutron star with an intense and largely dipolar magnetic field that is inclined with respect to the axis of rotation of the neutron star. A typical magnetic field in pulsars is on the order of 1014 G.

Pulsars emit a large amount of radiation via a physical process called synchrotron radiation. Free electrons with high velocities (near the speed of light) surrounding the neutron star have curved trajectories in the magnetic field due to the Lorentz force. The magnetic field lines therefore accelerate these relativistic particles that in turn causes synchrotron radiation. The emission spectrum of the synchrotron process emits more radiation energy in the short-(X- ray) and especially the long-(radio) wavelength portions of the electromagnetic spectrum as compared to blackbody (or thermal) radiation. Pulsars therefore emit a relatively large amount of radio radiation. Two cones of radiation, similarly to lighthouse beacons, sweep across space as the neutron star rotates. Pulsars maybe observed if one of the paths of these cones of radiation crosses the position of the Earth. Pulses of radiation can then be detected, which is why these astronomical objects are called pulsars.

The first pulsar was discovered in 1967 by the British astronomers Anthony Hewish (b. 1924) and Jocelyn Bell Burnell (b. 1943) with observations in the radio region of the electromagnetic spectrum. Up to now, over 1500 pulsars have been identified. Most of these pulsars have been detected in the radio region of the electromagnetic spectrum, while some were detected with X-rays. The best-known pulsar is the one at the centre of the Crab nebula (M1) found in the constellation Taurus. M1 is the remnant of a supernova observed in 1054 and recorded by Chinese and Arab astronomers.