NGC 1161 and NGC 1160 in Perseus
October 2024 - Galaxy of the Month
For this month I am choosing the nice pair of galaxies in Perseus, NGC 1161 and NGC 1160. Both of these galaxies were discovered by William Herschel in 1784, although NGC 1160 was also independently rediscovered by R.J. Mitchell using Lord Rosse’s 72” at Birr.
NGC 1161 is classified as a Seyfert galaxy with a classification of 1.9 (or possibly type 2), it is also classified as an AGN of the LINER type. NGC 1161 is a lenticular galaxy of type S0 whilst NGC 1160 is classified as a flocculent spiral of type SBc, or possibly Scd, seen close to edge on. The distance given for NGC 1160 is about 116 million light-years so it lies quite a bit beyond NGC 1160 which lies at about 90 million light-years.
NGC 1160 does seem to have a lot of star formation going on in it given the blue nature of its spiral arms. This is slightly unusual as lying in the void there is nothing for it to interact with to cause all this star formation. The galaxies are not a physical pair but both lie near the centre of the local void between our local supercluster and the Perseus cluster, Abell 426.
As a quick aside it appears that most galaxies lie on filaments on the edge of voids where very few galaxies appear to be. This means by studying galaxies in voids we can see how they evolve when not disturbed by interactions.
There is a nice amateur image of the pair by José Manuel López Arlandis on Astrobin. See also the Mantrap Skies Catalog entry for these galaxies which shows an interesting HST image of the internal part of NGC 1161 which appears to show an inner ring of dust clouds.
There does not appear to be much research done on either of these two which I find quite surprising as there is always interest in galaxies that are evolving without interacting with others. Perhaps as expected the area also has issues with galactic cirrus for imagers.
NGC 1161 does make it into the Astronomical League's Herschel II list but, perhaps as expected, not into any other observing lists.
The galaxies are a very tight pair and will fit into the field of view of a high-power eyepiece. There is a bright double star on the edge of NGC 1161 which may hinder viewing, HJ 2167. It is actually a triple star system with the third star lying in NGC 1161. The The Night Sky Observer's Guide (NSOG) Volume 1, now sadly out of print, suggests that the pair are targets for 40-45cm telescopes but I would have thought that since William Herschel found both of them, they should be visible in smaller apertures, perhaps down to 20-25cm.
Owen Brazell - Galaxy Section Director
If you'd like to try out the Clear Skies Observing Guides (CSOG), you can download observing guide for the current Galaxy of the Month without the need to register. CSOG are not associated with the Webb Deep-Sky Society but the work of Victor van Wulfen.
