Highly compressed matter in which the normal atomic structure has broken down and which, because of quantum-mechanical effects, exerts a pressure that is independent of temperature. Bodies with masses <1.4 Msun (e.g., white dwarfs) are supported by The force that supports white dwarf stars against gravity. Quantum mechanics restricts the number of electrons that can have low energy. When electrons are packed together, the number of available low energy states is too small and many electrons are forced into high energy states. When this happens the electrons and have Mass of an object divided by its volume. Density is a characteristic property of a substance (rock vs. ice, e.g.). Some substances (like gases) are easily compressible and have different densities depending on how much pressure is exerted upon them. The Sun is composed of compressible gases and is much of ~106 kg/m3. If the mass of a collapsed Self-luminous object held together by its own self-gravity. Often refers to those objects which generate energy from nuclear reactions occurring at their cores, but may also be applied to stellar remnants such as neutron stars. >1.4 Msun, Attractive force between all matter - one of the four fundamental forces. will overwhelm electron degeneracy and further collapse ensues. Electrons combine with protons to form neutrons, so producing a Dense ball of neutrons that remains at the core of a star after a supernova explosion has destroyed the rest of a star with mass 8-18 (?) Msun. A neutron star has mass ~2-3 Msun, density ~1014 g/cm3, and is supported by neutron degeneracy pressure. Typical neutron stars are 10-20. Because neutrons, like electrons, are subject to the Pauli exclusion principle, at high enough densities ~1014 kg/m3, Charge-neutral hadron with a mass of 1.6748 x 10-27 kg, equivalent to 939.573 MeV, and an intrinsic angular momentum, or spin, of ½ (in units of h/2π). The neutron is a nucleon, one of the two basic constituents of all atomic nuclei (apart from 1H, which consists of a single degeneracy pressure prevents further collapse of the star. For masses >2-3 Msun, even neutron degeneracy can’t prevent further collapse, and a Maximally gravitationally collapsed object predicted to exist by the theory of general relativity, from which no material object, light or signal of any kind can escape. Many black holes form when a high mass supergiant star explodes in a supernova explosion at the end of its life. A star probably is formed.
Some or all content above used with permission from J. H. Wittke.