Amateur astronomers dubbed this object M110 in the 1960s, so we choose not to include it. Charles Messier’s list stops at 103 objects. Historically, that should be the last word, but it would be hard to stop there. Imagine excluding the Sombrero Galaxy (M104) from the list! Some sources also include NGC 205, a companion to the Andromeda Galaxy.
Astronomy recognizes 109 Messier objects. The additional six in the list, including M104, were first described in 1783 by French astronomer Pierre Méchain (1744-1804), a contemporary of Messier. — Michael Bakich, senior editor