Black holes white dwarfs and neutron stars pdf

Concept art of a black dwarf against black holes white dwarfs and neutron stars pdf background field of stars. A black dwarf is a theoretical stellar remnant, specifically a white dwarf that has cooled sufficiently that it no longer emits significant heat or light.

The name “black dwarf” has also been applied to substellar objects that do not have sufficient mass, less than approximately 0. These objects are now generally called brown dwarfs, a term coined in the 1970s.

Black dwarfs should not be confused with black holes, black stars, or neutron stars. What is left is then a dense sphere of electron-degenerate matter that cools slowly by thermal radiation, eventually becoming a black dwarf.

If black dwarfs were to exist, they would be extremely difficult to detect, because, by definition, they would emit very little radiation. They would, however, be detectable through their gravitational influence. 2012 by astronomers using MDM Observatory’s 2. They are estimated to be 11 to 12 billion years old.

Because the far-future evolution of stars depends on physical questions which are poorly understood, such as the nature of dark matter and the possibility and rate of proton decay, it is not known precisely how long it will take white dwarfs to cool to blackness. If protons are not stable, white dwarfs will also be kept warm by energy released from proton decay.

For a hypothetical proton lifetime of 1037 years, Adams and Laughlin calculate that proton decay will raise the effective surface temperature of an old one-solar-mass white dwarf to approximately 0. Although cold, this is thought to be hotter than the cosmic background radiation temperature 1037 years in the future. Once the Sun stops fusing helium in its core and ejects its layers in a planetary nebula in about 8 billion years, it will become a white dwarf and, over trillions of years’ time, eventually will no longer emit any light.

After that, the Sun will not be visible to the equivalent of the naked human eye, removing it from optical view even if the gravitational effects are evident. Look up black dwarf in Wiktionary, the free dictionary.

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