Black Hole

Also referred to as quantum singularity, an enormous concentration of mass the gravity of which is so strong that even light is not able to escape. The radius inside which this effect becomes evident is called event horizon.

Basically, a black hole is supposed to accumulate energy, never ever emitting anything of it. Stephen Hawking, however, postulated that black holes do actually emit radiation, or shrink in terms of mass. This strange behavior is attributed to the quantum uncertainty. According to quantum mechanics, it is in no way prohibited that a particle/antiparticle pair is generated from nothing, as long as their lifetime is so short that it is not noticed. If this happens at the event horizon, one particle might fall into the black hole, whereas the other could escape. In this case it would seem as if the black hole does emit radiation, and the Romulans obviously take advantage of this effect.

The existence of black holes has been confirmed by real world physics. There are different types and sizes of black holes, some of them actually existing, others assumed possible. Their common characteristic is the strong gravitational force that causes any kind of mass/energy to fall towards its center, once it is inside the event horizon. The mass concentration in the center is possibly beyond the current laws of physics. Even the elementary particles that form the atom nucleus under normal conditions might be crushed and further compressed to an unknown degree, with a density close to infinity, which is referred to as singularity.