The ring in the gas component, with velocity vectors. The ring is rotated so as we see it face-on (x and y coordinates have the subscript ‘rp’ to denote that these are coordinates in the plane of the ring). A combination of rotation and expansion away from the ring centre can be seen, resulting in a twist in the velocity field away from radial expansion. Despite a mildly off-centre collision, the ring remains close to circular and expands at a roughly uniform velocity; however, the nucleus is clearly off-centre within the ring.