Stephan's Quintet - Hubble Space Telescope

Stephan's Quintet is a visual grouping of five galaxies of which four form the first compact galaxy group ever discovered. The group, visible in the constellation Pegasus, was discovered by Édouard Stephan in 1877 at the Marseille Observatory. The group is the most studied of all the compact galaxy groups. Wikipedia

 

Note 1:

If you are wondering where the five galaxies area and can only count four, the structure in the upper right-hand position which looks like a smiling face is actually composed of two galaxies interacting together - NGC 7318A and NGC 7318B.

 

Note 2:

Redshift - Stephan's Quintet => Hickson Quartet

NGC 7320, the blue-ish spiral galaxy in the lower left has a redshift of only 790 km/s, while the other four galaxies exhibit a much larger redshift of approx. 6600 km/s. Since galactic redshift is proportional to the distance from Earth, NGC 7320 is actually not part of this grouping but only appears that way. It is located in front of the other four by about 39 million light years from Earth versus the 210-340 million light years of the other four. This has caused some astronomers to call the other four the "Hickson Quartet" rather than Stephan's Quintet.

 

Data acquisition: Hubble Legacy Archive, NASA

Data processing: Rudy Pohl

Image: RGB colour

Processing software: Fits Liberator, Photoshop CS5

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