Mayall's Object - ARP 148
Mayall's Object (Arp 148) is almost certainly the result of a collision between two galaxies; perhaps a small galaxy passing through a larger galaxy. The collision produced a shockwave that first drew matter into the center and then caused it to propagate outwards in a ring. The elongated companion perpendicular to the ring suggests that Arp 148 is an ongoing collision. It is in the constellation of Ursa Major, the Great Bear, and is more than 150 Mpc (about half a billion light-years) away. Image Credit.