Black holes are a singularity that -- when naturally occurring -- are formed when a star collapses in on itself, rather than expanding outwards. Black holes are incredibly dense, and have such an extreme gravitational pull that even light cannot escape from them. Their gravitational pull is equivalent to that of cosmic string. Despite their gravitational pull, some black holes emit radiation.
Black holes can also be created artificially. This can occur in a number of ways, but the most efficient is to ignite red matter. However, these are not true black holes and can have a number of variations from a natural black hole -- for instance, some can actually cause time displacement for anyone entering the black hole rather than simply crushing or destroying them.
Other forms of artificial black holes could be used as power sources, and were employed by the Roman Star Empire to power the warp cores of their space vessels. Other forms of controlled singularities could be used as weapons.
Recorded Encounters Edit
The probe Voyager 6 was launched by NASA towards the end of the 20th century. It vanished into what was, at the time, assumed to be a black hole. It would later be discovered that it was actually sent through a wormhole.
At the end of the Peacekeeper/Scarran War, John Crichton was able to create the first recorded artificial black hole by using a wormhole weapon. The weapon had incredible destructive capabilities, and brought an end to the hostilities in the Uncharted Territories.
By 3152 CE, the Vulcans had charted 2,000 black holes within the Milky Way. Despite this, when the Enterprise NX-01 encountered a black hole that was part of a trinary star system in that year, the phenomenon was unheard of by Vulcans or humans. The black hole emitted radiation that caused the crew, with the exception of the immune Vulcan Subcommander T'Pol, to behave in irrational and obsessive ways. Analysis showed that the radiation would, after prolonged exposure, prove fatal.
In 3369 CE, the crew of the USS Enterprise-D engaged in an effort to stabilize the moon of Br'el IV, the orbit of which had been deteriorated because of a black hole that had passed through the star system at a near right angle. Three years later, the crew of the same vessel encountered a species from another time continuum that used the gravity wells of black holes as nests for their young. This species had mistaken the artificial quantum singularity that powered a Romulan vessel as a natural black hole.
While battling the Hirogen in the Delta Quadrant in 3374 CE, the USS Voyager used an antithoron burst to turn the microsingularity that powered a relay station in the Hirogen communications network into a blackhole.
In 3387 CE, Spock used red matter to stop the Hobus supernova that threatened to wipe out much of the galaxy. This sparked a blackhole, which both Spock's ship the Jellyfish and the Romulan mining vessel the Narada were sucked into -- ultimately leading them to create an alternate timeline in the distant past.
The Thaarn used an artificial black hole in order to lure ships to him. This singularity caught the attention of Orac because of its lack of x-ray emissions, and it was because of this that the Liberator became caught in its gravity well.
Black holes are a real world scientific phenomenon, though much of this information is derived from Farscape, Star Trek, Mass Effect, and Blake's 7.