- This page is about the astronomical phenomena; for the film, see Event Horizon.
An event horizon is an extremely powerful energy field which surrounds certain astronomical phenomena which have high gravitational attractions, such as singularities, wormholes, and cosmic strings. At the event horizon, the escape velocity equals the speed of light, making escape from the gravity well impossible under normal circumstances.
In 2371, the USS Voyager became trapped within the event horizon of a type 4 quantum singularity in the Delta Quadrant. Encountering time-delayed reflections from the interior of the horizon, the Voyager crew initially believed that they had encountered another vessel being pulled into the singularity. Eventually, they were able to locate a breach in the event horizon, which they had created when they initially entered the phenomenon, by saturating it with warp particles. Although the breach had decreased in size since their arrival, they were able to widen it with a dekyon beam and escape. (VOY: "Parallax")