This
Astrobin Debut Object is a galaxy group of 4 spiral galaxies, called Hickson 71, located in the constellation of Bootes at a declination of +25 degrees.
3 of these galaxies are at similar distances from us, lying between 420 and 440 million light years away, but the 4th is much further away.
Because all of these galaxies are spirals, this is one of the dimmest Hickson objects in terms of mean surface brightness.
The largest and brightest galaxy, Hickson 71a, is also known as NGC 5008. It spans 1.1 arc-minutes, which corresponds to a large diameter of 140,000 light years. Located 440 million light years away, it is a pretty, slightly barred grand design face-on spiral with a fascinating arm structure. From each end of the bar, 2 strong arms emanate in clockwise directions. But after a short 45 degree rotation, a weak branch separates from each arm and falls back to the opposite bar end, forming a pseudo-ring around the mid-region.
Edge-on spiral Hickson 71b is about the same size and distance away as 71a, although I don’t see any signs of interaction. Hickson 71c is slightly closer and smaller, while 71d is the outlier at almost 1 billion light years away.
The Hickson catalog is a collection of 100 galaxy groups, established by Paul Hickson in 1982. Hickson compact galaxy groups are tightly spaced and somewhat isolated 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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