A black dwarf is a theoretical stellar remnant, specifically a white dwarf that has cooled sufficiently to no longer emit significant heat or light. Because the time required for a white dwarf to reach this state is calculated to be longer than the current age of the universe, no black dwarfs are expected to exist in the universe at the present time. The temperature of the coolest white dwarfs is one observational limit on the universe's age.
Diagram of stellar evolution, showing the various stages of stars with different masses
In astronomy, the term compact object refers collectively to white dwarfs, neutron stars, and black holes. It could also include exotic stars if such hypothetical, dense bodies are confirmed to exist. All compact objects have a high mass relative to their radius, giving them a very high density, compared to ordinary atomic matter.
The Eskimo Nebula is illuminated by a white dwarf at its center.
The Crab Nebula is a supernova remnant containing the Crab Pulsar, a neutron star.
A simulated black hole of ten solar masses, at a distance of 600 km