Abell 347 in Andromeda

November 2021 - Galaxy of the Month

Near to the well-known edge on galaxy NGC 891 lies the small group of galaxies known as Abell 347. The cluster is relatively poor in Abell terms but contains 7 galaxies: NGC 906, NGC 909, NGC 910, NGC 911, NGC 912, NGC 914 and NGC 923.

The cluster is part of the Perseus-Pisces Supercluster, which also includes the clusters Abell 262 and Abell 426. The Perseus-Pisces super cluster is thought to be the most massive object within 300 million light-years. More information on the filament can be found at The Atlas of the Universe.

NGC 898 and NGC 910 were discovered by William Herschel in 1786. NGC 906, NGC 909, NGC 911 and NGC 914 were found by Stephan in 1878, and Dreyer found NGC 923 in 1874. NGC 898 is sometimes included as part of the cluster but appears to lie outside the core region. There was some thought that the active galaxy 3C66A was part of the cluster but it is now thought to lie well behind in another cluster.

Abell 347 probably lies at a distance of about 240 million light-years, and is classified as a richness class 0 and a distance class 1 in the Abell classification scheme. Here richness goes from 0 (least rich) to 5 (most rich) in terms of galaxy numbers. It has a putative Rood-Shastry class of I.

The Brightest Cluster Galaxy (BCG) is probably the large elliptical NGC 910. It has also been classified as a cD galaxy. However most of the brighter galaxies in Abell 347 appear to be spirals which suggests that this is a young group and the expected mergers have not yet taken place. Perhaps surprisingly there does not seem to have been much research done on this cluster.

Although some sources list over 57 galaxies in the cluster the Webb Deep-Sky Society Observer's Handbook (WSDSOH) Volume 5 lists 20 that may be visible in medium large instruments under good skies, There is a nice diagram as well as observing reports on the clusters in the Perseus-Pisces filament at Adventures in Deep Space.

Observationally the group is fairly compact and most of the main galaxies, with the exception of NGC 898 and NGC 914, will fit in a single medium power (270x) field using a modern hyperwide eyepiece. My suggestion, given the faintness of these galaxies, is to use the highest power you can to get the contrast up. My observations under poor skies using a 55cm showed most of the main galaxies, but I did not pick up any of the MCG galaxies in the field.

There is an article on the Skyhound website on observing this group. Unfortunately most images of the cluster are usually framed to fit in NGC 891 so the area of interest is rather small. I suspect this group has been overlooked because its proximity to NGC 891.

My apologies for the brevity of the material in this piece but I have been suffering from Covid whilst writing it.

Owen Brazell - Galaxy Section Director