Cecilia Payne

Now recognized as one of the most brilliant astronomers of the twentieth century, credited with determining what stars are made of, this week’s WiSE Wednesday honoree, Cecilia Payne, was born in Wendover, England in 1900. She entered Cambridge University interested in a broad array of sciences, but was unsure which field to specialize in until she heard a public lecture from the astronomer Arthur Eddington and was hooked. She had the chance to talk with him at an event for the public at the Cambridge Observatory, after which he literally opened doors for her, allowing her access to the Observatory’s vast library resources. Cambridge did not offer degrees to women at that time, however, so Cecilia set her sights on the U.S., where she was the first person to earn a PhD in astronomy from Harvard’s Radcliffe college, for work that would revolutionize the field of astrophysics.

By attaching spectroscopes to their telescopes, scientists can spread out wavelengths contained in light coming from stars. As the light travels through the star’s atmosphere, some of it is absorbed by chemical elements. Different elements absorb different wavelengths of light, so the resultant spectrum provides valuable information about the composition of the star. Because the spectra of starlight were similar to the spectra of elements in earth’s crust, most astronomers believed that earth and stars had similar compositions. However, in her groundbreaking PhD thesis, Cecilia showed that, when temperature was taken into account, the spectra of starlight showed that stars are almost entirely composed of the two lightest elements: hydrogen and helium. This finding was so unorthodox that a prominent Princeton astronomer, Henry Norris Russell told her that her conclusion was “clearly impossible.” Nevertheless, Payne converted her thesis into a book, Stellar Atmospheres, in which she also presented a method to use starlight spectra to calculate the temperature of stars. Her work was shown to be accurate, and is now generally accepted. Even Russell came around, publishing similar findings several years later (he acknowledged Cecilia’s work, but he is often solely credited for the conclusion they independently reached).

After obtaining her PhD in 1925, Cecilia remained at Harvard until she retired from teaching in 1966 (although she continued to contribute to astrophysics). Despite performing the duties of a professor, gender discrimination prevented her from achieving professor status until 1956, when she became Harvard’s first female full professor and first female department head. While she was never elected to the National Academy of Sciences, Cecilia did have the ironic honor of receiving the Henry Norris Russell Prize.

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