A group of five apparently interacting galaxies, one of which shows a very different redshift from the other four. These four (NGC 7317, 7318A and B, and 7319) are probably physically associated, with redshifts implying a recessional velocity of 5700 to 6700 km/s, while NGC 7320 has a redshift implying a recessional velocity of 800 km/s and is now recognized to be a foreground object superimposed by chance. Hence the group should perhaps be renamed Stephan's Quartet. The group, which lies about 250 million l.y. away in Pegasus, is named after the French astronomer Édouard Jean Marie Stephan (1837–1923), who discovered it in 1876.
Subjects: Astronomy and Astrophysics.