Which of the following does not fit with the others? Please explain your reasoning.
Galaxy M81
Black Eye Galaxy
Pinwheel Galaxy
Andromeda Galaxy
Sombrero Galaxy

Galaxy M81 does not fit with the other 4 in the list as M81is a designation rather than a proper name. The other 4 galaxies listed also have a designation, e.g Sombrero Galaxy is designated M104. M81 also has a proper name, Bode's Galaxy. But as listed, Galaxy M81 is distinct from the rest of the list.