M109 - NGC 3992

Messier 109 (NGC 3992) is a barred spiral galaxy located approximately 67 million light-years from Earth in the constellation Ursa Major. It was discovered by Pierre Mechain in 1781 and is one of the more distant galaxies in the Messier catalog. M109 is classified as an SBbc barred spiral and has a visual magnitude of about 9.8 with a physical diameter of approximately 180,000 light-years, making it one of the largest Messier galaxies. The galaxy features a prominent central bar from which two main spiral arms emerge and wind outward through the disk. M109 is the brightest member of a large galaxy group known as the NGC 3992 Group or M109 Group, which contains over 50 member galaxies. The galaxy is located very close to the star Phecda (Gamma Ursae Majoris) in the bowl of the Big Dipper, lying only about 40 arcminutes southeast of this bright star. While Phecda makes M109 easy to locate by star-hopping, the star's brightness can also interfere with observation of the galaxy by causing glare. M109 has a relatively low surface brightness, making it somewhat challenging for visual observers despite its respectable total magnitude. A supernova, SN 1956A, was observed in M109 in 1956. In amateur telescopes, M109 appears as a faint, oval glow with a slightly brighter center. An 8-inch telescope under dark skies can show the overall shape and hint at the bar structure, while larger instruments may reveal more of the spiral arm pattern. The galaxy's association with the Big Dipper asterism makes it one of the most conveniently located Messier galaxies, though its distance and low surface brightness make it less visually impressive than closer spirals.

M109 spans approximately 180,000 light-years in diameter, one of the largest Messier galaxies, located about 67 million light-years from Earth.