NGC 7320 indicates a small redshift (790 km/s) while the other four exhibit large redshifts (near 6600 km/s).
 Since galactic redshift is proportional to distance, NGC 7320 is only a foreground projection and is ~39 million lightyears from Earth versus the 210-340 million lightyears of the other four.

NGC 7319 has a type 2 Seyfert nucleus.

A sixth galaxy, NGC 7320C, probably belongs to the Hickson association:  it has a redshift similar to the Hickson galaxies, and a tidal tail appears to connect it with NGC 7319.
NGC 7320 indicates a small redshift (790 km/s) while the other four exhibit large redshifts (near 6600 km/s).  Since galactic redshift is proportional to distance, NGC 7320 is only a foreground projection and is ~39 million lightyears from Earth versus the 210-340 million lightyears of the other four.
NGC 7319 has a type 2 Seyfert nucleus.
A sixth galaxy, NGC 7320C, probably belongs to the Hickson association:  it has a redshift similar to the Hickson galaxies, and a tidal tail appears to connect it with NGC 7319.
Stephan's Quintet