NGC 3631 (also Arp 27, IRAS 11181+5326, MCG 9-19-47, UGC 6360 and PGC 34767) is a magnitude +10.3 face-on spiral galaxy located 53 million light-years away in the constellation Ursa Major. The galaxy is listed as Arp 27 in the Atlas of peculiar galaxies by Halton Arp because the spiral arms have an asymmetric appearance.
The galaxy was discovered by German-British astronomer William Herschel using a 47.5 cm (18.7 inch) f/13 speculum reflector at Windsor Road, Slough, on the 14th April 1789.
The galaxy has hosted supernova 1964A, SN 1965L, SN 1996bu and SN 2016bau.
Right Ascension 11h 21m 02.7s, Declination +53° 10' 11"
