Galaxy Messier 109
Charles Messier is probably the discoverer of this galaxy when, in March, April or May 1781, he checked the position of three «nebulae» that his colleague Pierre Méchain had told him (today M 97, M 108 and this one here). Apparently, Messier only had the opportunity to measure one of these three before his publication (M 97). Shortly after his observation, he noted the position in his personal copy of the catalog. The position was strange because the right ascension went well with NGC 3953 and γ UMa, while the declination went well with NGC 3992. Therefore it seems possible that he had seen both galaxies and was the actual discoverer of NGC 3992. When Owen Gingerich verified the location in 1953, he identified this object with NGC 3992 and added it to the official Messier catalog as the M 109.
It was not until October 2006, when Henk Bril examined the maps of Fortins Atlas from 1795, that he found out that Pierre Méchain did not discover NGC 3992, but the neighboring galaxy NGC 3953. This is why one sometimes finds the designation M 109B for NGC 3953. 
M 109 is the brightest member of a group of about 80 galaxies known as the Ursa Major Galaxy Cluster. It is a bar-spiral galaxy of the morphological type SB(rs)bc and is home to around one trillion stars. The distance is approximately 18 Mpc to 29 Mpc (58 to 94 million) light years. The appearance of the galaxy could be due to the influence of three neighboring galaxies (UGC 6923, UGC 6940, UGC 6969). [145, 215]
|Name||RA [hms]||Dec [dms]||mType||Dim [']||Btot [mag]||HRV [km/s]||PA [°]|
|PGC 37553||11 56 49.8||+53 09 41||I||2.0 x .8||14.0||1066||175|
|PGC 37617, NGC 3992, M 109||11 57 36.2||+53 22 31||SB||7.5 x 4.4||10.6||1048||68|
|PGC 37621||11 57 41.1||+53 15 18||S||1.0 x .2||16.8||1108||136|
|PGC 37700||11 58 40.8||+53 25 18||IB||1.6 x .5||15.2||1113||152|
The galaxy M 109 is located in the constellation Ursa Major only 38 arc minutes from γ Ursae Majoris. It is circumpolar and is highest in the night sky from December to June.