UGC 12158: A Milky Way Look-Alike with a Supernova

UGC 12158, or PG 69533, is a barred spiral galaxy located in the constellation Perseus. It is thought by many to resemble what the Milky Way Galaxy would look like from afar, with a relatively small bar and distinct spiral arms. Barred spirals, as the name suggest, feature swirling arms of stars that emanate from a bar-shaped center. Such bar structures are common, being found in about two-thirds of spiral galaxies, and are thought to act as funnels, guiding gas to their galactic centers where it accumulates to form newborn stars. These aren’t permanent structures: astronomers think that they slowly disperse over time, so that the galaxies eventually evolve into regular spirals. This image also contains a short-lived and brilliant interloper — a supernova seen at the 7 o’clock position about halfway out from the galaxy’s center and on the inner edge of a spiral arm. This stellar explosion, called SN 2004ef, was first spotted by two British amateur astronomers in September 2004. The other bright stars in the frame are ones within our own galaxy that chance to be along the line of sight to UGC 12158.