Stephan's
Quintet (which is also known as Hickson 92 and Arp 319), is a famous group
of five galaxies discovered by Edouard Stephan in 1877 at Marseille Observatory.
Four of these galaxies are interacting gravitationally, spreading stars
into great arcs and "tails". This group also provides several challenges
for the owners of larger telescopes.
The largest and brightest galaxy is NGC 7320. It is just visible in a six-inch scope as an elongated hazy patch. Larger instruments may show mottling in the outer parts. This galaxy has a much lower redshift and is likely to be between us and the other members of the quintet.
You will need at least an 8-10" scope and dark skies to see the other galaxies of this group, which are apparently part of the same galaxy cluster. At 100x they appear as a close grouping. Use higher magnifications to study the individual galaxies.
A few arc minutes to the northwest of NGC 7320 you will see two apparently interacting members (NGC 7318A and NGC 7318B). Taken together they appear nearly as large as NGC 7320 at the eyepiece. Look for their bright cores and a hint of a spiral arm just to the east of the center of NGC 7318B.
To the northeast of this pair lies NGC 7319, a face-on barred spiral. Look for a hint of spiral structure on the outer northeastern edge.
The final member, NGC 7317, lies to the southwest of the NGC 7318 pair, and is a typical featureless elliptical galaxy.
While you are in the neighborhood,
don't miss the nearby galaxy NGC 7331 which lies less than a degree to
the northeast. As galaxies go, this one is bright and well defined.
| Galaxy | RA | Dec | Mag | Size | Mean
Surface Brightness (mag/arc-sec2) |
Notes |
| NGC 7317 | 22h35m52s | +33o56'43" | 14.7 | 23" x 33" | 21.2 | Elliptical, z=0.02 |
| NGC 7318A | 22h35m57s | +33o57'54" | 14.3 | 36" x 32" | 21.7 | Elliptical, z=0.02 |
| NGC 7318B | 22h35m58s | +33o57'55" | 14.0 | 1.3' x 0.7' | 22.5 | Face-on barred spiral, z=0.02 |
| NGC 7319 | 22h36m04s | +33o58'36" | 14.2 | 1.3' x 0.9' | 23.0 | Face-on barred spiral, z=0.02 |
| NGC 7320 | 22h36m04s | +33o56'53" | 13.3 | 1.9' x 1.1' | 22.8 | Nearly face-on spiral |
| Millennium
Star Atlas Vol III Chart 1142
Sky Atlas 2000 Chart 9 Uranometria 2000 Vol I Chart 123 Herald-Bobroff Astroatlas B-05 C-21 |
