Accretion disk

An accretion disk is a structure that is created when matter falls into a gravitational source, like a wormhole.

The Barzans theorized that radiation buildup in the Barzan wormhole's accretion disk was responsible for its brief visible burst every 233 minutes. 

An accretion disk was present in a subspace compression anomaly studied by the USS Defiant (2370) and the USS Rubicon in 2374. Entering this accretion disk caused the runabout to shrink.