Black hole

Black Holes are the cores of collapsed stars, a place where gravity is so great that nothing, not even light, can escape its pull. These black holes are generally thought to be dangerous occurrences, but some species are able to use and control black holes. One of the Time Lords, Omega, discovered a way to harness their energy, creating the Eye of Harmony. (DW: The Three Doctors) The Nimons based most of their technology on artificial black holes, especially for long distance transportation. (DW: The Horns of Nimon)

One known black hole contains an alternate universe made of anti-matter, in which Omega was trapped. (DW: The Three Doctors) Another black hole, K37J5, was found with a planet orbiting it (which, as the Doctor proclaimed, is impossible). (DW: The Impossible Planet, The Satan Pit)

Some scientists believe that there is a black hole in the center of most galaxies, including the Milky Way. Whether this is true in this universe is unknown.