Portrait of the American astronomer Annie Jump Cannon (1863-1941). In 1895 Cannon entered the Radcliffe College to study astronomy and in 1896 she was appointed to the staff of the Harvard College Observatory. She worked there for the rest of her career, serving from 1911 to 1932 as curator of astronomical photographs. She was responsible for the compilation of the Henry Draper Catalogue containing a quarter of a million stellar spectra. She developed a new spectral classification system which since then has only slightly altered. She grouped stellar spectra in nine classes O, B, A, F, G, K, M, R and N in terms of decreasing surface temperatures.
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