Four of the galaxies have large redshifts, corresponding to recession velocities of 5,700 to 6,700 km/s; however, the fifth member (NGC 7320) has a much smaller redshift equivalent to a line-of-sight recession of only 800 km/s. This anomaly has led a few astronomers to question the validity of the cosmological explanation (see discordant redshift). However, the lower redshift system is almost certainly a foreground object that is unconnected with what should properly be called Stephen's Quartet.
The cluster is named after the French astronomer Éouard Stephan (1837–1923), who discovered it in 1877.
Related category GALAXIES
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