Everything about Black Dwarf totally explained
A
black dwarf is a
hypothetical star, created when a
white dwarf becomes sufficiently cool to no longer emit significant
heat or
light. Since the time required for a white dwarf to reach this state is calculated to be longer than the current
age of the universe, 13.7 billion years, no black dwarfs are expected to exist in the
universe yet, and the temperature of the coolest white dwarfs is one observational limit on the
age of the universe.
A
white dwarf is what remains of a
main sequence star of low or medium mass (below approximately 9 to 10
solar masses), after it has either expelled or
fused all the
elements which it has sufficient temperature to fuse. What is left is then a dense piece of
electron-degenerate matter which cools slowly by
thermal radiation, eventually becoming a black dwarf. If black dwarfs were to exist, they'd be extremely difficult to detect, since, by definition, they'd emit very little radiation. One theory is that they might be detectable through their
gravitational influence.
Since the far-future evolution of white dwarfs depends on physical questions, such as the
nature of
dark matter and the possibility and rate of
proton decay, which are poorly
understood, it isn't known precisely how long it'll take white dwarfs to cool to blackness.
, § IIIE, IVA. Barrow and Tipler estimate that it would take 10
15 years for a white dwarf to cool to 5
K; however, if
weakly interacting massive particles exist, it's possible that interactions with these particles will keep some white dwarfs much warmer than this for approximately 10
25 years. These objects are now generally called
brown dwarfs, a term coined in the 1970s. Also, black dwarfs shouldn't be confused with
black holes or
neutron stars.
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