NGC 969 in Triangulum

December 2020 - Galaxy of the Month

This interactive image of the NGC 969 group was provided by the Pan-STARRS1 Surveys using Aladin Sky Atlas. We also have a finder chart that should help you identify these galaxies, as will this link for NGC 969 on the Stellarium Web planetarium.

NGC 969 is part of a trio of galaxies along with NGC 974 and NGC 970 in Triangulum. NGC 969 and 974 were discovered by John Herschel in November 1827 using his 18.3” reflecting telescope. NGC 970 was discovered by Bindon Stoney using the 72” at Birr in September 1850. On the same night he though he saw another object, which was added to the NGC as NGC 971 but this was later shown to be just a star. Some sources however still attribute this number to the faint companion galaxy to NGC 970, including for instance Megastar 5.

NGC 969 and 974 are listed as part of a 5 galaxy group, listed as WBL 077, that also includes NGC 978, but not NGC 970 as that would appear to be much further in the background. NGC 970 is also listed as an interacting pair in the extended Vorontsov-Velyaminov (VV) catalogue as VV 1034. I am puzzled however because although the WBL catalogue listing does not include NGC 970 as part of the group NASA/IPAC Extragalactic Database (NED) does include it as WBL 077-3.

Interestingly although NGC 978 is not listed as part of the trio it probably should be as it fits in the same high power field. It too was discovered by John Herschel in 1827. It is also listed as an interacting galaxy in the VV catalogue as VV 1035. It would appear to be interacting with the galaxy listed as NGC 978B. NGC 974 is also gravitationally interacting as it is showing what appears to be long tidal tails or extended spiral arms in deep images.

The group lies at a distance of perhaps 200 million light-years from us. NGC 969 is classified as an S0, a, lenticular galaxy but shows what appears to be a bar so perhaps SB0 might be a better classification for it. Perhaps surprisingly there does not seem to be a lot of research done specifically on this group. Both NGC 978 and its companion are listed as lenticulars but in the PanSTARRS image it appears there may be a third galaxy associated, either that or there is a knot in NGC 978B.

Observationally the group maybe a challenge as the brightest galaxy (NGC 969) is around 13th magnitude and then it goes fainter. However, as John Herschel saw them all then (at least the main three) I would hope that a 40cm should be able to pick them up. NGC 970 is likely to be much tougher as that required the Birr 72” to find.

The main trio is very compact and will take high power if the seeing and condition will allow it. I would be interested to know what power would be needed to visually split NGC 978 and 978B, my suspicion is probably over 300x. I note that the Night Sky Observer's Guide (NSOG) suggests that NGC 969, NGC 974 and NGC 978 should be visible in 30/35cm scopes but suggest that to split NGC 978 A and B would require a 55cm scope at medium power. UK observations by Mark Stuart suggest a 35cm is required for NGC 969 but it was not very prepossessing. He also reported observations of NGC 974 and 978 with the same and larger telescopes that also suggested they did not show much detail.

Owen Brazell - Galaxy Section Director