Stellar spectral types originally followed alphabetical order. But as astronomers observed more stars and obtained more detailed spectra, they consolidated some categories and reordered the remaining ...

I. ALTHOUGH the observations made by Fraunhofer in 1814 first indicated that the spectra of stars were not all of the same character, it was the more systematic observations of Rutherfurd and Secchi ...

The following is an excerpt from The Glass Universe: How the Ladies of the Harvard Observatory Took the Measure of the Stars, by Dava Sobel. The monumental work of stellar classification known as the ...