This
Astrobin Debut Object is a galaxy cluster located 0.4 billion light years away in the constellation of Bootes at a declination of +25 degrees. The larger galaxies here are each about 100,000 light years in diameter.
Hickson 69 is the group of 4 galaxies at center, as annotated in the mouseover. The Hickson catalog is a collection of 100 galaxy clusters, established by Paul Hickson in 1982. Hickson compact galaxy clusters are tightly spaced relative to other space objects. A typical Hickson cluster has 4 galaxies, but some have up to 8. The criteria implies that a Hickson group cannot be part of a larger cluster, but you can see here that Hickson 69 is surrounding by other galaxies that are also at a similar distance away. Hickson 69 is an exception to the rule of not being part of a larger cluster, simply because they are no galaxies immediately adjacent to Hickson 69 (within one diameter of a circle sized to contain Hickson 69).
Hickson 69a, also known as UGC 8842, is the largest galaxy at center. It is an edge-on spiral with a mid-line dust lane and a core that is offset to the left. It spans 1.3 arc-minutes, which corresponds to a diameter of 160,000 light years. This is the only galaxy of the 4 in Hickson 69 that appears disturbed to me.
All of the galaxies here are primarily yellow with the exception of LEDA 49523 (just above Hickson 69), whose blue color is likely due to recent star formation.
Comments