Messier 109

Lore & Background

Messier 109 was discovered by Pierre Méchain in 1781. Two years later Charles Messier catalogued the object, as an appended object to his publication. Between the 1920s through the 1950s, it was considered that Messier objects over 103 were not official, but later the additions, further referred target objects from Méchain, became more widely accepted. David H. Levy mentions the modern 110 object catalog while Sir Patrick Moore places the limit at 104 objects but has M105 to 109 listed as addenda. By the late 1970s all 110 objects were in common use among astronomers and remain so to this day.

M109 has three satellite galaxies (UGC 6923, UGC 6940 and UGC 6969) and possibly more. Detailed hydrogen line observations have been obtained from M109 and its satellites. M109's H I distribution is regular with a low-level radial extension outside the stellar disc, while in the bar is a central H I hole in the gas distribution. Possibly the gas has been transported inwards by the bar, and because of the emptiness of the hole no large accretion events can have happened in the recent past.

One supernova has been observed in M109: SN 1956A (Type Ia, mag. 12.3) was discovered by Howard S. Gates on 8 March 1956, using the 18-inch Schmidt telescope at the Palomar Observatory. It was located 67" east and 9" south of the center of the galaxy.

Reader's Guide

Messier 109 holds significance as the most distant object in the Messier Catalog, a fact that underscores its value for studying galaxy evolution at greater distances. Its status as the brightest member of the M109 Group, a large group possibly numbering over 50 galaxies, makes it a key reference for understanding group dynamics. The galaxy's history reflects the evolving acceptance of Messier objects beyond 103, with debate between astronomers like David H. Levy and Sir Patrick Moore until the late 1970s when all 110 objects became commonly used. The observation of SN 1956A, a Type Ia supernova discovered by Howard S. Gates in 1956, provides a specific data point for supernova studies. The detailed hydrogen line observations revealing a regular H I distribution with a central hole in the bar suggest that gas has been transported inward without recent large accretion events, offering insights into the galaxy's internal processes. M109 can be seen south-east of the star Phecda (γ UMa) in Ursa Major, aiding amateur astronomers in locating it.

Did You Know?

• Messier 109 is the most distant object in the Messier Catalog, followed by M91.
• The only observed supernova in M109, SN 1956A, was discovered by Howard S. Gates on 8 March 1956.
• M109 is the brightest galaxy in the M109 Group, which may contain over 50 galaxies.