This month, as spring is upon us, sees the second richest concentration of galaxies within 100 million light years make its grand appearance in our skies...the Fornax Supercluster. Composed of two major clusters of galaxies, the Fornax and Eridanus Clusters, plus several other smaller groups, the average distance to the supercluster is around 70 million light years. The Fornax Cluster itself lies at a distance of around 62 million light years and contains 58 major galaxies and a host of smaller dwarfs.
NGC1316: The largest galaxy of the Fornax Cluster is NGC1316, also known as Fornax A. At the given distance of the cluster, the SO type (lenticular) galaxy spans 215Kly (215000 light years). It is a powerful radio source and is believed to have a central black hole upwards of 1 billion solar masses. As with all large galaxies, it is a cannibal and has swallowed many a smaller galaxy and may still be undergoing the process.
NGC1365: A beautiful barred spiral galaxy (SBb), NGC1365 is the second largest member of the cluster, spanning some 205Kly (205000 light years). It exhibits the classic barred central (formed from the co-rotation of stars, dust and gas about the nucleus of the galaxy) structure common to around 60% of all galaxies. It has been notable in the number of supernovae that have flared up in the galaxy within the last 50 or so years...SN2001du, SN1973V and SN1957C. It lies a little closer than most of the cluster at 56 million light years.
NGC1399: The central galaxy of the cluster, NGC1399 is a giant elliptical galaxy of the type cD. Whilst its overall size is smaller than either NGC1316 or 1365 (at 130Kly or 130000 light years), it is considerably more massive. Noted to contain several thousand globular clusters, the galaxy shines at mag 10.3 from a distance of 62 million light years.
Other galaxies of note within Fornax are NGC1350 (SBab, 110Kly), NGC1344 (cD, 105Kly) and NGC1425 (Sb, 115Kly)
The neighbouring Eridanus Cluster of galaxies lies a bit further away than Fornax at an average distance of 80-85 million light years. It is also a richer cluster, having around 75 major galaxies.
NGC1398: The largest galaxy of the cluster, some 175Kly (175000 light years) in size, lies near the outer edge of the cluster at a safe distance from the two most massive galaxies of the cluster, two large cD galaxies (NGC1407 and 1395). A type SBab barred spiral, the nucleus of this galaxy is particularly bright, with the spiral arms forming a ring around the nucleus. It shines with a magnitude of 10.5.
NGC1407: A large elliptical galaxy (type cD) it lies at the centre of one subgroup of the Eridanus Cluster and is some 125KLy (125000 light years) across. Like most elliptical galaxies, it is a fairly bland ball of stars, surrounded by thousands of globular clusters, many of which came from other galaxies which were cannibalised by the massive elliptical. It shines at mag 10.9.
NGC1395: Another large elliptical of type cD, and much like NGC1407 in its structure, this galaxy lies at the centre of the other subgroup within the main galaxy cluster. Some 140Kly (140000 light years) in size, it is somewhat larger than NGC1407 and is consequently a bit brighter, at mag 10.7. Much like the other elliptical, it is surrounded by thousands of globular clusters.
Other galaxies of note within Eridanus are NGC1300 (SBbc, 150Kly), NGC1371 (SBa, 140Kly), NGC1332 (cD, 105Kly) and NGC1325 (SBbc, 115KLy).
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