부산대학교 도서관

A star containing about 1½ solar masses of material compressed into a volume approximately 6 mi (10 km) in radius. (1 solar mass equals 4.4 × 1030 lbm or 2.0 × 1030 kg.) Neutron stars are one of the end points of stellar evolution and are the final states of stars that begin their lives with considerably more mass than the Sun. The density of neutron star material is 1014 to 1015 times the density of water and exceeds the density of matter in the nuclei of atoms. Neutron stars are pulsars (pulsating radio sources) if they rotate sufficiently rapidly and have strong enough magnetic fields. Neutron stars play a role in astrophysics which extends beyond their status as strange, unusual types of stellar bodies. The interior of a neutron star is a cosmic laboratory in which matter is compressed to densities which are found nowhere else in the universe. Precise measurements of the rotation of neutron stars can probe the behavior of matter at such densities. Neutron stars in double-star systems can emit x-rays when matter flows toward the neutron star, swirls around it and heats up. Neutron stars are almost certainly formed in supernova explosions, events in which a dying star becomes more luminous than an entire galaxy, up to 1012 times as powerful as the Sun. A few pulsars are found in double-star systems and careful timing of the pulses they emit can test Einstein's general theory of relativity.