Accretion disk
From Memory Alpha, the free Star Trek reference
An accretion disk is a structure that is created when matter falls into a gravitational source, like a wormhole.
One of the theories as to why the Barzan wormhole remained stable for a time stated that a radiation buildup in the accretion disk was responsible for the phenomenon. (TNG: "The Price")
An accretion disk was present in a subspace compression anomaly studied by the USS Defiant and the USS Rubicon in 2374. Entering this accretion disk caused the Danube-class runabout to shrink. (DS9: "One Little Ship")
