NGC 777 in Triangulum

November 2023 - Galaxy of the Month

This interactive image of the NGC 777 and was provided by the Sloan Digital Sky Survey (SDSS) using Aladin Sky Atlas. We also have a finder chart should help you locate these galaxies, as will this link for NGC 777 on the Stellarium Web planetarium.

It is becoming harder to find interesting galaxies that are not too faint to feature in the GOM blog. This month I have chosen the pair of galaxies NGC 777 and NGC 778 in Triangulum.

NGC 777 was discovered by William Herschel in 1784 but the much fainter NGC 778 had to wait until 1866 when it was discovered by Safford using an 18” refractor at Dearborn observatory in the US, although it was independently rediscovered by Stephan in 1875 using the 30” silver of glass reflector at Marseille. Safford did not publish his observations until 1887, after the NGC was completed.

NGC 777 is an elliptical galaxy, classified as E1, with a weak active nucleus of the LINER or Seyfert 2 class. The nucleus shows as a bright X-Ray source. It may also be an outlying member of the cluster Abell 262. It lies at a distance of perhaps 187 million light-years. NGC 777 and 778 may form a non-interacting pair. NGC 777 is also included as part of a group of galaxies catalogued as LGG 42 which has 13 galaxies involved including NGC 750, NGC 751, NGC 761, NGC 777, NGC 783, NGC 785 and NGC 789, although interestingly not NGC 778.

NGC 778 has been classified as an S0, i.e. a lenticular galaxy and according to NED lies much further away than NGC 777 so they may just be an optical pair. It has also been classified as SAB(s)a, which fits with observations with the GALEX satellite in the UV suggest that there may be a ring of star formation in NGC 778 which would be at odds with its lenticular classification. The SDSS image also shows the suggestion of a bar and spiral arms. There are suggestions that NGC 778 may also be a starburst or Seyfert galaxy. NGC 777 just shows a bright core in the UV.

The The Night Sky Observer's Guide (NSOG) Vol 1 suggests that the pair should be visible in 12-14in (30-35cm) scopes as a faint pair. NGC 777 should be relatively easy and NGC 778 shows as a bright nucleus with a fainter halo. I suspect that as usual from the more polluted skies of the UK that it may well require 40cm to show the same views. Mark Stuarts observation of NGC 777 with a 40cm show it to be faint but there is no mention of him seeing NGC 778.

Owen Brazell - Galaxy Section Director