Black dwarf

For other uses, see Black dwarf (disambiguation).

A black dwarf is a hypothetical astronomical object: a white dwarf so old that it has cooled down so that it no longer emits significant heat or light. None are expected to exist yet, since the time required for a white dwarf to cool down is calculated to be longer than the age of the universe.

III==Evolution== A white dwarf star is what remains of a Sun-sized star after it has fused virtually all of its original hydrogen and helium fuel to heavier elements such as carbon, oxygen, and nitrogen and is unable to carry on any further fusion of the byproducts. It then begins to cool down by simple thermal radiation.

Even if black dwarfs did exist, they would be extremely difficult to detect, since by definition they would emit very little radiation (if any), or at most their radiation would be a temperature not much above that of the cosmic microwave background radiation. They may be detectable through their gravitational influence.

Both black dwarfs and white dwarfs are degenerate dwarfs.

Not in any way related to brown dwarfs

Black dwarfs should not be confused with the unrelated brown dwarfs, which are formed when gas contracts to form a star, but does not possess enough mass to initiate and sustain hydrogen nuclear fusion. "Brown dwarfs" were at times called "black dwarfs" in the 1960s. Neither should black dwarfs be confused with black holes or neutron stars, as neither is the result of the cooling of a white dwarf.

References

• Richmond, Michael. "Late stages of evolution for low-mass stars". Rochester Institute of Technology. Retrieved 2006-08-04.