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Stephan's Quintet, the first compact galaxy group ever described, was discovered by Édouard Stephanis in 1877 at Marseilles Observatory. He identified five tightly grouped galaxies, shown in the center of this image. The top right galaxy is a dull elliptical galaxy. Just below this are two converging spiral galaxies. The fourth, in the lower left center, is another interacting spiral, whose gravitational interaction with the other galaxies in this group is distorting their spiral arms. The brightest member of the visual group, in the lower right center, is the bluish spiral galaxy NGC 7320. Farther down in the image at 7:00 from the main group, a faint barred spiral with a symmetrical ring structure (NGC 7320C) is now considered an outlying member of the galaxy cluster.
Spectroscopy shows a small redshift for NGC 7320 but a much larger redshift for the other galaxies in the group. Because redshift correlates with distance, NGC 7320 is only 60 million light years away while the rest of the galaxy cluster is about 300 million light years distant.
This image combined 145 minutes of unbinned luminance exposures with 50 minutes of red, 50 minutes green and 70 minutes of blue exposures, binned 2x2. An ST10XME camera was used through a Meade 12" LX200R and an AP reducer at the Hidden Lake Observatory. |
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