M109 is one of the "Theta"-like barred spirals, which appears as a "hazy spot" situated just 40' SE of the mag 2.44 star Gamma Ursae Majoris (Phad, or Phecda). It was observed by Pierre Mechain on February 16, 1781, and by Charles Messier on March 24, 1781, together with M108 when they detected and measured M97, but M109, together with M108, were not added to the catalog until 1960, by Owen Gingerich.
M109 is about 7-by-4 arc minutes in angular extent, and of apparent visual magnitude 9.5 or 9.6. Visually, only its bright central region together with the bar can be seen, and appear pear-shaped in smaller telescopes, "with a strong suspection of a granular texture" (Mallas).
The type I supernova 1956A occured in this galaxy on March 17, 1956, and reached 12.8 mag in its maximum.
|Right ascension||11 : 55.0 (hours : minutes)|
|Declination||+53 : 39 (degrees : minutes)|