Nicknamed the "Census Taker of the Sky" for classifying 300,000 stellar bodies, the American astronomer Annie Jump Cannon played a leading role in the development of modern stellar classification. Her creation of the Harvard Classification Scheme marked the first attempt to properly classify stars based on their temperatures and spectral types.

A trailblazer for women in science, she combined two models to make her own system that used the simplified classes: O, B, A, F, G, K, M. Annie’s model would go on to be adopted worldwide and was given the mnemonic device “Oh Be A Fine Girl, Kiss Me”. When three additional categories (R, N and S) were added to the scheme, students invented a new mnemonic: Oh, Beautiful and Ferocious Gorilla, Kidnap My Roommate Next Saturday.