neutron star

neutron star
an extremely dense, compact star composed primarily of neutrons, esp. the collapsed core of a supernova.

* * *

Any of a class of extremely dense, compact stars thought to be composed mainly of neutrons with a thin outer atmosphere of primarily iron atoms and electrons and protons.

Though typically about 12 mi (20 km) in diameter, they have a mass roughly twice the Sun's and thus extremely high densities (about 100 trillion times that of water). Neutron stars have very strong magnetic fields. A solid surface differentiates them from black holes. Below the surface, the pressure is much too high for individual atoms to exist; protons and electrons are compacted together into neutrons. The discovery of pulsars in 1967 provided the first evidence of the existence of neutron stars, predicted in the early 1930s and believed by most investigators to be formed in supernova explosions. See also white dwarf star.

* * *

 any of a class of extremely dense, compact stars thought to be composed primarily of neutrons. Neutron stars are typically about 20 km (12 miles) in diameter but have a mass roughly the same as the Sun's. Thus, their mean densities are extremely high—about 1014 times that of water. This approximates the density inside the atomic nucleus, and in some ways a neutron star can be conceived of as a gigantic nucleus held together by its own gravity. In the centre of the star, where the pressure is greatest, the material is thought to consist mainly of hyperons and mesons. The intermediate layers are mostly neutrons and are probably in a “superfluid” (superfluidity) state. The outer 1 km (0.6 mile) is solid, in spite of the high temperatures, which might be as high as 1,000,000 K. The surface of this solid layer, where the pressure is lowest, is composed of an extremely dense form of iron.

      Another important characteristic of neutron stars is the presence of very strong magnetic fields (magnetic field), upwards of 1012 gauss, which causes the surface iron to be polymerized in the form of long chains of iron atoms. The individual atoms become compressed and elongated in the direction of the magnetic field and can bind together end-to-end, forming “whiskers,” which probably extend out from the surface. Below the surface, the pressure becomes much too high for individual atoms to exist.

 The discovery of pulsars (pulsar) in 1967 provided the first evidence of the existence of neutron stars. Pulsars are generally believed to be rotating neutron stars. The very short periods of the Crab (NP 0532) and Vela pulsars (33 and 83 milliseconds, respectively) rule out the possibility that they might be white dwarfs. The pulses appear to result from electrodynamic phenomena generated by their rotation and their strong magnetic fields, as in a dynamo. There is also evidence that certain binary X-ray sources, such as Hercules X-1, contain neutron stars. Cosmic objects of this kind appear to emit X rays by compression of material from companion stars accreted onto their surfaces.

      Most investigators believe that neutron stars are formed by supernova explosions in which the collapse of the central core of the supernova is halted by rising neutron pressure as the core density increases to about 1015 grams per cubic cm. If the collapsing core is more massive than about two solar masses, however, a neutron star cannot be formed, and the core would presumably become a black hole.

* * *

Universalium. 2010.

Look at other dictionaries:

  • Neutron star — redirects here. For the story by Larry Niven, see Neutron Star (short story). Neutron stars crush half a million times more mass than Earth into a sphere no larger than Manhattan. A neutron star is a type of stellar remnant that can result from… …   Wikipedia

  • neutron star — neutron stars N COUNT A neutron star is a star that has collapsed under the weight of its own gravity …   English dictionary

  • neutron star — ☆ neutron star n. a collapsed star of extremely high density composed almost entirely of neutrons: pulsars are generally thought to be rotating neutron stars …   English World dictionary

  • Neutron Star —    A Pulsar whose density is so great that the electrons have been stripped from the atoms that compose the star. It is the dead core of a star, all that remains after a supernova. A Neutron Star may be only a few kilometers across, but have more …   The writer's dictionary of science fiction, fantasy, horror and mythology

  • neutron star — neu′tron star n. astron. an extremely dense, compact star composed primarily of neutrons, esp. the collapsed core of a supernova • Etymology: 1934 …   From formal English to slang

  • neutron star — noun a star that has collapsed under its own gravity; it is composed of neutrons • Hypernyms: ↑star • Hyponyms: ↑pulsar …   Useful english dictionary

  • neutron star — noun A degenerate star that has been so collapsed by gravity that its electrons and protons have been merged into neutrons by the intense pressure. The solid mass of neutrons is sometimes called neutronium …   Wiktionary

  • neutron star — noun Astronomy a celestial object of great density composed predominantly of neutrons, believed to be formed by the gravitational collapse of a star …   English new terms dictionary

  • neutron star — /njutrɒn ˈsta/ (say nyoohtron stah) noun a star with a diameter of about 10 km and a mass between three and four times that of the sun, postulated as the result of a gravitational collapse in which electrons and protons coalesce into neutrons …   Australian English dictionary

  • neutron star — noun Date: 1934 a dense celestial object that consists primarily of closely packed neutrons and that results from the collapse of a much larger stellar body …   New Collegiate Dictionary

Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”

We are using cookies for the best presentation of our site. Continuing to use this site, you agree with this.