Warp trail

A warp trail, also known as an ion trail, is a wake in subspace which is left by a starship using warp drive. A warp trail can be detected by sensors, but their are ways of masking them, such as traveling through a nebula.

In April 2151, the Enterprise (NX-01) followed a Suliban cell-ship into the atmosphere of a gas giant after following its warp trail. 

Shortly after entering an unnamed star system near the Klingon Neutral Zone, Lieutenant Gary Mitchell aboard the USS Constitution (NCC-1700) detected an ion trail in orbit of one of the system's three planets. After following the trail, the Constitution was met by a Klingon battle cruiser, the.