A pulsar is a highly magnetized rotating neutron star that emits beams of electromagnetic radiation out of its magnetic poles. This radiation can be observed only when a beam of emission is pointing toward Earth, and is responsible for the pulsed appearance of emission. Neutron stars are very dense and have short, regular rotational periods. This produces a very precise interval between pulses that ranges from milliseconds to seconds for an individual pulsar. Pulsars are one of the candidates for the source of ultra-high-energy cosmic rays.
PSR B1509−58 – X-rays from Chandra are gold; Infrared from WISE in red, green and blue/max.
Chart on which Jocelyn Bell first recognised evidence of a pulsar, exhibited at Cambridge University Library
Composite optical/X-ray image of the Crab Nebula, showing synchrotron emission in the surrounding pulsar wind nebula, powered by injection of magnetic fields and particles from the central pulsar.
The Vela Pulsar and its surrounding pulsar wind nebula.
A neutron star is a collapsed core of a massive supergiant star. The stars that later collapse into neutron stars have a total mass of between 10 and 25 solar masses (M☉), possibly more if the star was especially rich in elements heavier than hydrogen and helium. Except for black holes, neutron stars are the smallest and densest known class of stellar objects. Neutron stars have a radius on the order of 10 kilometers (6 mi) and a mass of about 1.4 M☉. They result from the supernova explosion of a massive star, combined with gravitational collapse, that compresses the core past white dwarf star density to that of atomic nuclei.
Central neutron star at the heart of the Crab Nebula
Radiation from the rapidly spinning pulsar PSR B1509-58 makes nearby gas emit X-rays (gold) and illuminates the rest of the nebula, here seen in infrared (blue and red).
A computer simulation depicting a neutron star with accretion disk, spewing out X-rays through the magnetic axis
NASA artist's conception of a "starquake", or "stellar quake"
