NGC 3561

NGC 3561, also known as Arp 105, is a pair of interacting galaxies NGC 3561A and NGC 3561B within the galaxy cluster Abell 1185 in Ursa Major. It was discovered by British astronomer John Herschel on 30 March 1827. Its common name is "the Guitar" and contains a small tidal dwarf galaxy known as Ambartsumian's Knot that is believed to be the remnant of the extensive tidal tail pulled out of one of the galaxies.
One supernova has been observed in NGC 3561A: SN 1953A was discovered by Halton Arp on 16 April 1953.