This
Astrobin Debut Object is a galaxy group of 4 galaxies, called Hickson 39, located 1 billion light years away in the constellation of Hydra at a declination of -1 degrees. All of these galaxies are classified as ellipticals, although at this distance it is hard to know for sure.
This is true cluster - the 4 galaxies are all about the same distance away. Hickson 39a and 39b appear to be interacting, with a faint star stream bridge between them.
The largest and brightest galaxy, Hickson 39a, spans only 18 arc-seconds, which corresponds to a diameter of 90,000 light years. This is one of the dimmest Hickson "a" galaxies at a magnitude of 15.1.
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.
This is one of those fields of views where there are more galaxies in the background than stars.
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