This rarely imaged object is a pair of magnitude 16 interacting galaxies located about 1 billion light years away in the constellation of Cetus at a declination of -7 degrees. Each galaxy spans about 20 arc-seconds in our apparent view, which corresponds to an actual diameter of 100,000 light years. Dr. Arp classified this object in the category of “Galaxies with Associated Rings”.
PGC 509 is the ring and PGC 510 is its companion. It is believed that PGC 510 passed through PGC 509 to create the resulting ring. The ring is blue suggesting new star formation as a result of the severe disturbance.
The above explanation is convenient but it seems to me that such a collision should have resulted in extended star streams from the gravitational forces. Perhaps these star streams are present but it is just too hard to see them when they are a billion light years away.
For those of you interested in these types of objects, my Astrobin collection of collisional ring galaxies is
here.
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