A Kerr loop created from superstring material
A superstring was an astronomical phenomenon that could result in the formation of a Kerr loop.
In 2344, a temporal rift which was the formation of a Kerr loop from superstring material, was created through the intense weapons fire in a battle between the USS Enterprise-C and four Romulan Warbirds at the Klingon outpost at Narendra III. The Enterprise-C was inadvertantly responsible for the creation of an alternate timeline when it drifted into the rift and traveled through time. (TNG: "Yesterday's Enterprise")