A tidal tail is a thin, elongated region of stars and interstellar gas that extends into space from a galaxy. Tidal tails occur as a result of galactic tide forces between interacting galaxies. [...] Tidal forces can eject a significant amount of a galaxy's gas into the tail; within the Antennae Galaxies, for example, nearly half of the observed gaseous matter is found within the tail structures.
Had to look up what tidal tails even were.