Nightscapes & Deep Sky Colors
Astrophotography © Brian A. Morganti
NGC 7331 Spiral Galaxy
& Stephan's Quintet
Mouse over the above image to see the designations of the various objects
The spectacular spiral galaxy NGC 7331 is shown in the upper right of this image and is located in the constellation of Pegasus. This galaxy is located about 40 million light years away and was discovered in 1784 by William Herschel. The central bulge in NGC 7331 seems to be rotating in the opposite direction from the rest of the disk of the galaxy.
Many other smaller galaxies are located nearby as shown above NGC 7331 and are listed in the mouse over image as NGC 7337, NGC 7335, NGC 7336, and NGC 7340.
Stephan's Quintet (lower left corner of the image) is comprised of NGC 7319 (upper right in the group), NGC 7318A and 7318B (interacting, lower center in the group), NGC 7317 (lower left in the group) and NGC 7320C (above the group). There is a tidal tail coming off of NGC 7319 which seems to connect to NGC 7320C. The mouse over image will clearly identify their locations. NGC 7320, the brightest and largest galaxy (upper left by the group), which appears in the image to be a part of the group, is actually a foreground galaxy located about 40 million light years away, whereas the Quintet is located at a distance of about 290 million light years. NGC 7320 is shown to have extensive H II regions, identified as red blobs, where active star formation is occurring. The group was discovered by Edouard Stephan in 1877 in France at Marseilles Observatory and was the first compact group of galaxies discovered.
These galaxies are of interest because of their violent collisions. Four of the five galaxies in Stephan's Quintet form a physical association, Hickson Compact Group 92, and are involved in a cosmic dance that most likely will end with the galaxies merging. Radio observations in the early 1970s revealed a mysterious filament of emission which lies in inter-galactic space between the galaxies in the group. Two space telescopes have recently provided new insight into the nature of the strange filament, which is now believed to be a giant intergalactic shock-wave (similar to a sonic boom but traveling in intergalactic gas rather than air) caused by one galaxy (NGC 7318B) falling into the center of the group at several millions of miles per hour.
This image contains a few small and faint galaxies in addition to those listed above.