NGC 877 in Aries

October 2021 - Galaxy of the Month

NGC 877 is part of a small group of galaxies in Aries that includes NGC 870, NGC 871 and NGC 876. NGC 871 and NGC 877 were both discovered by William Herschel in October 1784 and R.J. Mitchell using Lord Rosse’s 72” found the other two in 1854.

NGC 877 and NGC 876 lie at the same distance from us, approximately 160 million light-years. NGC 877 appears to be interacting, probably with NGC 876. NGC 877 is the brightest galaxy in the LGG 53 group, an 8 galaxy group, which appears to include NGC 871 as well, but not NGC 870, which is interesting as NASA/IPAC Extragalactic Database (NED) describes NGC 871 as in a non-interacting pair with the compact elliptical galaxy NGC 870. The redshift of NGC 870 however suggests that it is a long way behind NGC 871. The group is also sometimes known as the NGC 877 group.

NGC 877 itself is classified as an intermediate spiral galaxy but also seems to be classified as a LIRG (Luminous Infrared galaxy) so one assumes there is quite a lot of star forming activity going on, indeed images in the UV from the GALEX satellite show numerous large areas of star formation going on in its spiral arms. Conversely NGC 876 shows very little activity in the UV. There appear to be some faint plumes coming off NGC 877. NGC 871 also appears very bright in the UV. It too is a spiral galaxy.

A low surface brightness bridge appears to connect NGC 877 and 876 which would confirm the interaction theory. NGC 876 is an edge on spiral with a central bulge and a distinctive dust lane, not unlike the one in NGC 891. Hubble has imaged both NGC 877 and 876 with the WPC 3 but only in the near IR and I have seen no processed images from this.

The group also has an extensive neutral hydrogen (HI) envelope, which suggests the group is gas rich. There is also an interesting gas cloud in the system which may be a tidally formed galaxy, although this appears to be a radio only object. NGC 870 maybe one of the most distant galaxies in the NGC.

The Night Sky Observer's Guide (NSOG) Volume 1 suggests the two brighter galaxies NGC 877 and NGC 871 should be in range of a 25cm telescope but the other two are probably going to require 45cm, at least from UK skies. A UK observation of NGC 877 suggests however that it is tough even with 40cm. The group is quite tight so will fit in the field of a medium to high power eyepiece. Indeed it is probably going to require a high power eyepiece to darken the field enough to catch the fainter pair.

It should be noted that Steve Gottlieb found both NGC 870 and NGC 876 very difficult even with a 18”. Owners of large telescopes may also be able to catch the galaxy UGC 1781 between the two pairs, however this is a face on spiral and at magnitude 14 is going to be a hard catch except among the best skies, at least for visual observers. I have seen no recorded observations of it.

NGC 877 was one of the galaxies reported by the Rosse team as spiral in nature. It also makes the Herschel 3 list and is listed, although not described, in Burnham's Celestial Handbook (BCH) Vol 1. There is a nice image of the group by Adam Block at Caelum Observatory.

Owen Brazell - Galaxy Section Director