Celestial hemisphere:  Northern  ·  Constellation: Ursa Minor (UMi)
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Hickson 84, Gary Imm
Hickson 84, Gary Imm

Hickson 84

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Hickson 84, Gary Imm
Hickson 84, Gary Imm

Hickson 84

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Description

This Astrobin Debut Object is a small galaxy cluster located 0.75 billion light years away in the constellation of Ursa Minor at a declination of +78 degrees.

The Hickson catalog is a collection of 100 galaxy clusters by Paul Hickson published in 1982. As seen here, I have imaged 30 of the 100 Hickson clusters. 

Hickson compact galaxy clusters are tightly spaced relative to other space objects. A typical Hickson cluster has from 4 to 7 galaxies.  This one has 6 officially, but I see at least 1 more that seems like it could have been part of this group.

I have labelled the galaxies in the mouseover. Hickson lettered his galaxies within each group starting with "A" being the brightest, and then working down the magnitude scale with sequential alphabet letters.  The largest and bright galaxy here, Hickson 84A (LEDA 58877), is 40 arc-seconds wide in our apparent view, which corresponds to a large diameter of 160,000 light years.  The entire cluster spans only 1 million light years.

The most interesting aspect of this image to me can only be seen upon close examination of the full resolution view or the mouseover.  Just below and right of the core of 84A is a tiny darker reddish object.  It looks like an artifact, but it is not since it also shows up in other images of Hickson 84.  Perhaps it is a small elliptical that is in the process of being absorbed, or a foreground planetary nebula.

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