Arp peculiar galaxies and
Hickson galaxy clusters are both fascinating categories to me. So when an object is both, I had to image it!
This object is a small galaxy cluster of 4 galaxies located 570 million light years away in the constellation of Pegasus at a declination of +9 degrees. The brightest galaxy is NGC 7609, a magnitude 15 galaxy. The other 3 galaxies are magnitudes 16 and 17. Based on velocity measurements, the lower left galaxy is much closer to us and is not related to the other 3. Each of the galaxies spans about 45 arc-seconds in our apparent view, which corresponds to an actual diameter for each of the 3 grouped galaxies of about 120,000 light years.
NGC 7609 appears to be an elliptical galaxy which MAY be interacting with the spiral galaxy (PGC 71077) just below it. Arp classified this object in the interesting category of “Galaxies with Jets”. The “jet” is the most fascinating part of this image. It is the almost straight stream of stars that seems to connect these 2 galaxies. It is not clear to me what is happening here. I don’t believe it is actually a jet of any sort. Its color suggests to me that it is part of the spiral galaxy. I guess it could be a type of 3rd arm of the spiral galaxy.
There is also an interesting small blue region, not much more than a blue dot, just to the left of the core of the elliptical galaxy, at the intersection with the upper arm of the spiral galaxy. If this is a star formation region, it would indicate that these 2 galaxies are indeed interacting.
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