High Quality Content by WIKIPEDIA articles! A black dwarf is a hypothetical stellar remnant, 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 of 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 ball of electron-degenerate matter which cools slowly by thermal radiation, eventually becoming a black dwarf. If black dwarfs were to exist, they would be extremely difficult to detect, since, by definition, they would emit very little radiation. One theory is that they might be detectable through their gravitational influence.