This
Astrobin Debut Object is a galaxy group of 4 galaxies, called Hickson 49, located in the constellation of Ursa Major at a declination of 67 degrees.
This appears to be true cluster - all 4 galaxies are about 0.5 billion light years away. To my eyes, they all are clearly disturbed and are likely to be interacting with each other. This is one of the few Hickson clusters where all appear to be disturbed like this. Also, it is unusual that these are all blue galaxies, likely due to star formation initiated by the gravitational interactions.
This Hickson cluster is so obscure that the largest and brightest galaxy, Hickson 49a, does not have a NGC, PGC, or UGC designation. 49a has a large star plume on the right side of the disk. The galaxy spans 20 arc-seconds, which corresponds to a small diameter of 50,000 light years. These are all small, distant disturbed galaxies.
The Hickson catalog is a collection of 100 galaxy groups, established by Paul Hickson in 1982. Hickson compact galaxy groups are strictly defined by 3 criteria: number of galaxies, total magnitude, and isolation from other galaxies. A typical Hickson group has 4 galaxies, but some have up to 8. You can see more about Hickson galaxy groups in my
Astrobin Hickson Collection.
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