Kerr loop
From Memory Alpha, the free Star Trek reference
A Kerr loop is an astrophysical phenomenon that can appear as a result of high-energy reactions in the presence of superstring material. It has the capacity of transporting material passing through it in both space and time.
The USS Enterprise-D encountered a Kerr loop that transported the USS Enterprise-C into the future from the Battle of Narendra III. (TNG: "Yesterday's Enterprise")
