Hickson 55 (VV172)

In this famous chain of galaxies the faintest member, second from the top (north) has a much greater redshift than the rest of the group. Why do groups often seem to have an anomalous member? A solution proposed in 1995 was that the mass of the real group acts as a gravitational lens to magnify and brighten any background galaxy in the same line of sight. This would produce more apparent discordant redshift members than pure chance would provide. David R.