neutron star

neutron star extremely small, extremely dense star, about double the sun's mass but only a few kilometers in radius, in the final stage of stellar evolution . Astronomers Baade and Zwicky predicted the existence of neutron stars in 1933. In the central core of a neutron star there are no stable atoms or nuclei; only elementary particles can survive the extreme conditions of pressure and temperature. Surrounding the core is a fluid composed primarily of neutrons squeezed in close contact. The fluid is encased in a rigid crystalline crust a few hundred meters thick. The outer gaseous atmosphere is probably only a few centimeters thick. The neutron star resembles a single giant nucleus because the density everywhere except in the outer shell is as high as the density in the nuclei of ordinary matter. There is observational evidence of the existence of several classes of neutron stars: pulsars are periodic sources of radio frequency, X ray, or gamma ray radiation that fluctuate in intensity and are considered to be rotating neutron stars. A neutron star may also be the smaller of the two components in an X-ray binary star.

neutron star Extremely small, dense star that consists mostly of neutrons. Neutron stars are formed when a massive star explodes as a supernova, blasting off its outer layers and compressing the core so that its component protons and electrons merge into neutrons. They are observed as pulsars. They have masses comparable to that of the Sun, but diameters of only c.20km (12mi) and average densities of c.10¹⁵g/cm³.