Four ring galaxies

Ring galaxies are probably the result of a collision, where a smaller more compact galaxy has passed through a larger more diffuse galaxy: its gravitational wake leaves the larger galaxy in this moderately stable configuration. Clockwise from top left, the galaxies are a) the Southern Ring, or Cartwheel, MCG 6-2-22A, at 00h35.2m, -33d58m (quite a stretch for a telescope near Tucson. Arizona), b) UGC 04414, MCG 4-20-058, at 08h24.5m, +21d44m, c) NGC2544 (along with its companion to the upper left, this is Karachentsev pair 160), at 08h20.6m, +74d15m, and d) II Herzog 4, at 08h55.7m, +37d17m. Galaxy c), and possibly galaxy b), are now thought more likely to be ringed galaxies, where the ring is in some respects an extension of spiral structure, and was not formed by a penetrating collision. These photographs were made at the Kitt Peak National Observatory's 4-meter Mayall telescope in 1973 and 1974 by Dr Roger Lynds. For the technical afficionado, each one was a 45-minute exposure on Kodak IIIAJ emulsion with a GG385 filter.