UGC 12158

UGC 12158 or PGC 69533 is an Sb-type barred spiral galaxy located approximately away from Earth in the constellation of Pegasus. Its tight spiral disk spans approximately, whose scale at heliocentric distance is about 36.9 kiloparsecs per arcminute. It is also often stated to resemble the Milky Way in appearance, with a similar central bar and spiral arm structure. The earliest known reference to this galaxy comes from part 2 of the Morphological Catalogue of Galaxies, published in 1964, where it is listed as MCG +03-57-032.

Supernova

On 4 September 2004, Tom Boles discovered a 18.5v magnitude Type Ia supernova on one of the spiral arms near the apparent centre in UGC 12158. It was independently discovered by Mark Armstrong the following day, and subsequently designated SN 2004ef. Optical spectra was obtained on 7 September 2004 confirming the Type I classification. It reached 17.0v magnitude on 9 September 2004 before fading from view. No progenitor star was found on earlier survey images.