Stephan’s Quintet, NGC7331 and Retinue

This image shows the galaxy group known as Stephan’s Quintet along with the spiral galaxy NGC7331 and a number of other galaxies (there are more then 20 in the image).

Click here for full-resolution image on Astrobin

To aid recognition the image is duplicated below with most of the galaxies labelled.

The field of view is about 42 arc-minutes wide by 34 high.

The largest galaxy in the image is NGC7331, a spiral some 40 million light years away. The four galaxies to its upper right, though referred to as part of the 7331 Group, are actually far in the background at a distance of over 300 million light years. They are sometimes referred to as ‘The Fleas’.

Stephan’s Quintet was the first compact galaxy group discovered, by Edouard Stephan in 1877. While four of the galaxies are a real association lying at a distance of 210-340 million light years, NGC 7320 is a foreground object at a distance of around 40 million light years. Ironically as its distance matches that of NGC7331 it could well be a member of that group rather than Stephan’s.

Technical details:

Planewave CDK-14 corrected Dall-Kirkham reflector, FLI Proline P9000 cooled CCD camera and filter wheel with Astrodon LRGB filters. Total exposure times were 8 hours Luminosity and 6 hours each through R, G & B filters. Processed in PixInsight.

As a footnote I have added a small image of another galaxy that appeared very near the edge of the original frame but which was eliminated from the main image because of colour gradients nearby.

This is NGC 7343. Small (<1 arcmin across) and faint at magnitude 14, it is nontheless a pretty barred spiral galaxy that deserves a showing. It is possibly a member of the distant Stephan’s group, over 200 million light years away.