Black dwarf

A black dwarf is a hypothetical late phase of stellar evolution. A black dwarf would be the last stage of a white dwarf when its energy is consumed and the surface temperature is fallen so far that neither heat nor visible light can be radiated more a significant extent. The prevailing opinion of astrophysics, the universe is 13.7 billion years with his not old enough to produce black dwarfs. The temperatures of the coolest white dwarfs correspond to the observable limit of the age of the universe.

A white dwarf is the remnant of a remaining in the main sequence star of low or middle initial mass ( under 9-10 solar masses ) after it has all the chemical elements that he could merge due to a sufficiently high temperature, merged or divested. The maximum mass of the white dwarf is 1.44 solar masses due to the Chandrasekhar limit. The remaining material is then sealed and degenerate and cools slowly by thermal radiation to eventually become a black dwarf. If black dwarfs should exist, it would be extremely difficult due to the lack or very low radiation to track them down. According to one theory, one could prove it by the action of its gravity.

Since the distant future development of white dwarfs depends on physical issues such as the nature of dark matter and the possibility and extent of proton decay is not known exactly how long it would take for the white dwarfs were cooled to their blackness., § IIIE, IVA. Barrow and Tipler estimate that it would take 1015 years for a white dwarf to cool down to 5 K. However, if WIMPs ( " weakly interacting massive particles " ) exist to white dwarfs could be due to interaction with these particles much longer, for a period of about 1025 years. Keeping warm, § IIIE. If the proton is not stable, the white dwarfs would also be kept hot due to the energy release in the proton decay. With an assumed lifetime of a proton from 1037, Adams and Laughlin calculated that the decay of protons would raise the effective temperature of an old white dwarf with about one solar mass to 0.06 K. Although it is very cold, it is assumed that this will be warmer than the temperature of the cosmic background radiation in 1037 years., § IVB.

Originally, the term " black dwarf " even when the objects precursor to stars was used which do not have sufficient mass of about 0.08 solar masses to fuse hydrogen. Since its introduction in the 1970s, however, the term has brown dwarfs enforced for such objects. Also black dwarfs should not be confused with black holes or neutron stars.