Cannon, Annie Jump (1863–1941)
American astronomer who compiled the enormously influential Henry
Draper Catalogue. Cannon was introduced to astronomy by her mother,
studied physics at Wellesley College, and specialized in astronomy at Radcliffe
College. In 1896 she was appointed by Edward Pickering
to the staff at Harvard College Observatory,
where she began to study variable stars
and stellar spectra. As color film was
not yet available, classification, tediously and with great difficulty,
by eye. In 1901 she published a catalogue of 1,122 southern stars, which
represented a sequence of continuous change from the blue-white stars of
types O and B,
with their strong helium lines, through types A,
F, G, and K,
characterized hydrogen and various metal lines, to the red stars of type
M with their spectral bands of titanium and
carbon oxides. It was not known at the time that this was a temperature
sequence. In 1910, her scheme was adopted by all observatories. Then came
her most famous work, the Henry Draper Catalogue, published by the
Harvard Observatory between 1918 and 1924, which lists the spectral types,
magnitudes, and positions of 225,300 stars, down to ninth magnitude –
every one classified by Cannon in person. In 1922, her system was adopted
by the International Astronomical Union as the
official system for the classification of stellar spectra. She then continued
the study down to eleventh magnitude and, in the process, discovered 277
variable stars and 5 novae. Among the many honors she received internationally
for her work, was the first honorary Ph.D. to be granted to a woman by Oxford
University.
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