Questar M-17

Questar M-17 is a dead star with a negative star mass, that is located at the edge of the Milky Way Galaxy.

While enroute to the planet Gateway in 2269, the USS Enterprise became trapped by the hypergravity produced by Questar. After establishing a stable orbit, the Enterprise discovered an unknown alien vessel also orbiting the star. (TAS episode/novelization: "Beyond the Farthest Star").