The Ladies of Observatory Hill (
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Before 1859 there were no working female astronomers
(Caroline Lucretia
Herschel was the Astronomer-sister of Sir William Herschel, discoverer of
Uranus. Annie Russell Maunder’s contributions were presented as those of her
husband Edward Walter Maunder, discoverer of the Maunder minimum in sunspot
activity.)
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Between 1859 and 1940 one-of-three astronomers was a woman.
What happened?
Photography was invented and great piles of data requiring
time-consuming analysis became available.
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Yet – no women’s names appear in textbooks of astronomy for this
period. They were hired to do simple
tasks, but were not allowed to marry or to progress professionally. Their average time of employment was 5 years.
Annie Jump Cannon (Born 1863 in Dover Delaware, Died 1941)
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Photographed millions of stars with a prism-equipped telescope.
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Catalogued them by “star type.”
Could recognize spectral lines where others saw only a smudge. Her measurements were later confirmed by
others with modern equipment.
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Not interested in “The Grand Fact.”
She never asked “why” and considered such questions to be an impediment
to her task.
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Since there was no male to attribute her work to, it is now known as
the “Harvard System” (but not the “Cannon”
system.)
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Inspired as a young girl by a lecture of Arthur Eddington. Studied at
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She examined the spectral lines, not only in terms of the Boltzmann equation,
but also the Saha equation.
Boltzmann – distribution of excited states as
function of T;
Saha – distribution of charge states (ionization) as function of T
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Only the visible spectrum was then accessible. She found lots of hydrogen, but H is not a
good tool for ground state absorption in in the UV, which doesn’t get through
the atmosphere.
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She tried H and K lines of Ca II (isoelectronic to K I). Here the 4s-4p transition at around 4000 A
does get through.
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She discovered that all stellar objects have essentially the same
elements in the same abundances, with hydrogen 60-80% and H + He 96-99%. She published it in her thesis in 1925.
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Henry Norris Russell and Arthur Eddington had their own model that
identified iron as the most abundant element, in disagreement with Payne’s
findings of an overwhelming abundance of hydrogen. They mounted an aggressive offense against
her, and she was powerless to defend against them. Unlike Galileo, she was not threatened with
torture and imprisonment. However, she
was forced to recant and to remain silent about her discovery concerning
hydrogen in order to retain her position.
·
In 1929 new evidence became available which caused Russell to flip, and
he wrote a book and took credit for the discovery.