degenerate matter


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Related to degenerate matter: Quark gluon plasma

degenerate matter

Matter in a highly dense form that can exert a pressure as a result of quantum mechanical effects. Degenerate matter occurs in white dwarfs and neutron stars. During the gravitational collapse of a dying star, the electrons are stripped from their atomic nuclei, and nuclei and electrons exist in a closely packed, highly dense mass. As the density increases, the number of electrons per unit volume increases to a point when the electrons can exert a considerable pressure, called degeneracy pressure. This pressure is a result of the laws of quantum mechanics. Unlike normal pressure, degeneracy pressure is essentially independent of temperature, depending primarily on density. At the immense densities typical of white dwarfs (107 kg m–3 or more) it becomes sufficiently large to counteract the gravitational force and thus prevents the star from collapsing further. The gross properties of a white dwarf are therefore described in terms of a gas of degenerate electrons.

Above a certain stellar mass (the Chandrasekhar limit) equilibrium cannot be attained by a balance of gravitational force and electron degeneracy pressure. The star must collapse further to become a neutron star. It is then the degeneracy pressure exerted by the tightly packed neutrons that balances the gravitational force. See also black hole.

degenerate matter

[di′jen·ə·rət ′mad·ər]
(physics)
Matter that has been stripped of its orbital electrons, so the nuclei are packed close together.
References in periodicals archive ?
In this latter, there is a mass limit (whose value depends from the specific state equation) for dense cores of degenerate matter: above this limit, nothing can stop the configuration from a final gravitational collapse with formation of event horizon and inner physical singularity.
Few observational, indirect, evidences for black holes existence have been performed in years but it seems that an alternative hypothesis of very compact degenerate matter configurations, permitted by nonsingular metrics, could be compatible with observations: let's consider, for example, a single nonrotating compact object of 9.2 solar masses (m=1 in units of (19)), in the singular metric, it would be a black hole, no matter of which state equation is used, and a "Schwarzschild radius" [r.sub.s] = 27.17 km would define the horizon event whose surface would have an infinite gravitational redshift and would surround a pointlike singularity.
These supernovas can leave behind a rapidly spinning neutron star (pulsar), composed primarily of neutron degenerate matter, which keeps this bizarre object bouncy against crushing gravity.
This material is, of course, termed quark degenerate matter, and it keeps what is left of what once was a very massive star bouncy despite a heartless crush.
The application of fully degenerate matter to the large planets and the white dwarfs was an unusual concept in light of a fully gaseous Sun.
But degenerate matter has an Achilles' heel: destroy the electrons and the star's supporting pressure vanishes.