August 2017 - Galaxy of the Month

NGC 6962 in Aquarius

August and astronomical dark finally returns to the UK. For this month’s GOM I have chosen the galaxy group around NGC 6962 in Aquarius.

NGC 6962 and its companion NGC 6964 were first discovered in 1785 by William Herschel (and not as some Wikipedia articles have it John). John Herschel then remeasured the positions later on. The situation in the area was then confused by observations by Lord Rosse and his team at Birr and Bigourdan. They discovered as many as 5 new nebulae in the field and Bigourdan getting confused managed to add two IC objects, that both turned out to be stars.

The whole story of the galaxies in this area is discussed by Harold Corwin in his notes on the NGC and IC catalogues. The original Rosse observations are attached to this piece as a PDF to give an idea of what their observations looked like. Remember that Rosse used GC (Herschel’s General Catalogue) numbers so the object that they knew as GC 4601 is equivalent to our NGC 6962.

NGC 6962 is probably the centre of a group of perhaps 7 galaxies listed as WBL 666. There are suggestions the group may contain up to 28 galaxies, however most of these are likely to be dwarfs discovered on the SDSS.

The core of the group has a number of peculiar E and S0 galaxies that suggests evidence of past interactions. The group is likely to be quite old and shows evidence of having a core halo structure. NGC 6962 is also a mild form of AGN as it is listed as a LINER.

The group is likely to be challenging to see visually and, whereas NGC 6962 and NCG 6964 are probably going to be visible in telescopes of perhaps 30cm-40cm aperture, I think to see the other galaxies in the group (those discovered by Rosse, well technically by Mitchell, using the 72”) may require telescopes of 50cm plus and good skies. The Night Sky Observer's Guide (NSOG) has NGC 6962 and NGC 6964 as targets for 40cm telescopes. It does not have any observations of the other galaxies in the area.

NGC 6962 itself is perhaps 180 million light years away and it had a supernova in 2002ha quickly followed by another in 2003dt. The arms that show up so well in images are very faint and it is likely that only the core of the galaxy will be visible. NGC 6292 is likely to be an intrinsically large galaxy. It has quite a complex morphological classification as SAB (r)ab and appears to be the only obvious spiral in the group, the others being lenticular or elliptical. That is unless UGC 11626 is part of the group.

Owen Brazell - Galaxy Section Director