The time between when the Winter and Summer Milky Way lie overhead in the Northern Hemisphere, i.e the Spring, is often considered by astroimagers, astronomers and the like to be “galaxy season”. Anywhere in the sky you look there are galaxies. Of course we often think of the brightest you can see: M51- the Whirlpool, M81- Bode’s Galaxy, the Leo triplet, M101- the Pinwheel etc. However lying much further out into space are galaxy clusters. These are more challenging to observe and require darker skies. In 1958, George Abell published his survey of over 2700 galaxy clusters which were observed at distances upwards of 850 megaparsecs or around 2-3 billion light years! The brighter galaxies, such as the ones mentioned above are typically 10’s of millions of light years distant, so the clusters you can see are much much farther away! The study of galaxy clusters is the study of the large scale structure of the universe and is of immense interest to astronomers and cosmologists. I decided to take a look at one of these with the Pier 2 wide field platform at the observatory.
The cluster known as Abell 1367 or the “Leo Cluster” is very well positioned now for observing. It lies at the eastern edge of the constellation Leo above the star Denebola and is high overhead when darkness begins.
There are a couple of things I discovered about this cluster, the first one I have actually imaged. It is one of the “closer” galaxy clusters at “only” 300 million light years with at least 70 major galaxies. Most dense galaxy clusters are composed mostly of elliptical galaxies. These appear as featureless ovoid patches of light with a central core. The Leo Cluster, however, contains mostly spiral galaxies, suggesting that it is much younger than other comparable clusters, such as the Coma Cluster. Along with the Coma Cluster, Abell 1367 is one of the two major clusters comprising the Coma Supercluster, which in turn is part of the “CfA2 Great Wall”, hundreds of millions of light years long, an immense galaxy filament and one of the largest known superstructures in the observable universe!
Many NGC named galaxies can be observed in the cluster. These are the brighter ones. The brightest is NGC 3842 shown with the white arrow. This is an elliptical galaxy and is home to one of the largest black holes ever detected, close to 10 billion times the mass of our Sun!
The observation of galaxy clusters is certainly well within the reach of amateur equipment and provides a compelling glimpse into the large scale structure of our universe!
Thanks for reading!