Over 20 million light-years away and swimming within the boundaries of the constellation Pisces, NGC 660's peculiar appearance marks it as a polar ring galaxy. A polar-ring galaxy is a type of galaxy in which an outer ring of gas and stars rotates over the poles of the galaxy. These polar rings are thought to form when two galaxies gravitationally interact with each other. One possibility is that a material is tidally stripped from a passing galaxy to produce the polar ring seen in the polar-ring galaxy. The other possibility is that a smaller galaxy collides orthogonally with the plane of rotation of the larger galaxy, with the smaller galaxy effectively forming the polar-ring structure. The first polar-ring elliptical galaxies were identified in 1978.
