Harvard spectral classification The Harvard system is a one-dimensional classification scheme by astronomer Annie Jump Cannon, who re-ordered and simplified the prior alphabetical system by Draper (see next paragraph).Click to see full answer. Correspondingly, what are the 7 spectral classes of stars?Stars are classified by their spectra (the elements that they absorb) and their temperature. There are seven main types of stars. In order of decreasing temperature, O, B, A, F, G, K, and M. O and B stars are uncommon but very bright; M stars are common but dim..Also Know, what does Obafgkm mean? Acronym. Definition. OBAFGKM. Oh, Be A Fine Girl/Guy, Kiss Me (mnemonic for the order of star temperatures) Also question is, what is the Morgan Keenan spectral classification system? Morgan-Keenan Luminosity Class. Classification of stars is based primarily on their temperatures. The Harvard spectral classification scheme assigns each star a spectral type which is further divided into 10 sub-classes depending on the absorption features present in the spectrum.Why are the stellar types arranged as Obafgkm?Originally, stars were assigned a type A to Q based on the strength of the hydrogen lines present in their spectra. Continuity of other spectral features was also improved if B came before A and O came before B, with the end result, the spectral sequence: OBAFGKM.