NGC 2537 in Lynx
March 2026 - Galaxy of the Month
This month’s galaxy is NGC 2537, also known as the Bear Paw galaxy, in Lynx. I am surprised that I have not covered this galaxy before in the GOM series although it was the object of the season in 2017.
NGC 2537 was first discovered by William Herschel in 1788, he added it to his class IV objects suspected to be planetary nebulae. NGC 2537 is described a s blue compact dwarf although it also has an SB(rs)dm classification. It is suspected of interacting with the edge on galaxy IC 2233, although neither shows any sign of interaction despite being at the same distance. The pair lie somewhere between 20 and 40 million light-years from us. Arp added NGC 2537 to his catalogue of peculiar galaxies as Arp 6, faint spiral galaxies. NGC 2537 also appears in the Vorontsov-Velyaminov catalogue of interacting galaxies as VV 138. Historically it was one of the galaxies that the Rosse team thought were spiral galaxies from observations with the 72” at Birr.
IC 2233 itself is classified as a superthin galaxy and is much fainter than NGC 2537 and was discovered by Isaac Roberts photographically in 1894 with his 20” telescope.
Interestingly in images from the GALEX satellite in the ultraviolet both NGC 2537 and IC 2233 seem to be forming stars at a high rate. In IC 2233’s case this is odd as radio observations suggest it does not contain much HI gas. The GALEX image of NGC 2537 also appears to show some spiral arms unlike the visual light images.
NGC 2537 is a physically very small galaxy with a diameter of perhaps 20,000 light-years, much smaller than our Milky Way at 100,000 light-years. There are a large number of bright HII regions in NGC 2537 which give it its distinctive shape. There is another small galaxy catalogued as NGC 2537A about 5’ of arc away but this galaxy is likely to be in the background.
Visually NGC 2537 is likely to be a challenge, although there are reports of it being seen with a 5” telescope. I suspect that from UK skies probably 30cm will be needed, certainly to see any structure in it. NGC 2537 did not make any of the standard Astronomical League Herschel observing lists although it was added to the H300 list of faint galaxies. Both NGC 2537 and IC 2233 will fit in the same field of view at medium power (say 260x) but IC 2233 is very much fainter and will require good skies to find. I have seen both from the UK using my old 50cm telescope although IC 2233’s visibility depends very much on the sky conditions.
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.
