Cecilia Payne: The Silent Star of Astrophysics
In the expansive realm of science, the revolutionary work of the underrepresented has often been misattributed to those with gender privilege. When it comes to conferring who discovered the categorization of the stars, credit is given to Henry Norris Russell, the prominent American astronomer who developed the Hertzsprung-Russell diagram to map stellar development. The textbooks credit Russell for discovering that the Sun’s composition differs from the Earth’s. They don’t tell you that he adopted this fundamental idea from his female student’s thesis four years after he rejected it in 1925. Nor do they tell you that this student, Cecilia Payne-Gaposchkin, is the unsung genius behind our modern understanding of variable stars, the connection between temperature and the stellar catalog, and the composition of the universe itself.
Cecilia Payne was born on May 10th, 1900 in England to a mother who later refused to pay for her college education. Nonetheless, Payne won a full scholarship and entered the University of Cambridge in 1919, where she completed her studies in natural sciences but could not receive a degree due to the lack of female intellectual recognition at Cambridge until 1948. At a London lecture by physicist Sir Author Eddington on Einstein’s general relativity, she was inspired to pursue astronomy in the United States, where women were more accepted in exploring the scientific field. She studied at the Harvard College Observatory after receiving a fellowship in 1923, where she befriended astronomer Annie Jump Cannon and her all-female team as they worked to categorize the spectral signatures of stars.
At the time, it was widely agreed that the composition of the Earth matched that of the Sun in elemental makeup and percent composition, since the most pronounced features of the star spectral class were calcium, iron, and other heavy elements that reflected the Earth’s contents. Russell himself further supported this by claiming that if the Earth were heated to incandescence, its spectrum would resemble that of the Sun.
After two years of deciphering Cannon’s data and calculating what the collective stellar spectra would look like over a wide range of temperatures, Payne noticed that her results matched the method of stellar classification that Cannon had been using to distinguish her data. For context, this method, today known as the Morgan-Keenan system, involves the categorization of stellar spectra into seven types: O, B, A, F, G, K, and M. In Payne’s thesis to Russell, she challenged common scientific thought by stating that Cannon’s method of stellar classification actually portrayed a temperature range for stars, in which O was the hottest and M was the coolest. She also stated that the stars were composed nearly entirely of hydrogen and helium, antithetical to the idea of matching proportions between the Sun and the Earth’s compositions.
Soon came the point at which Russel rejected Payne’s thesis and would not concede to her correctness until 1929. However, her genius did not go entirely unrecognized during this time. Astronomers Velta Zebergs of Cannon’s team and Otto Struve called her thesis “undoubtably the most brilliant Ph.D. thesis ever written in astronomy.”
Harvard did not grant doctoral degrees to women at the time of Payne’s endeavor anyway, so she went on to become the first woman to receive a Ph.D. in astronomy from Radcliffe College in 1925, just after Russell’s initial rejection. Later on, she continued her work in stellar spectra and wrote the book Stars of High Luminosity (1930), which brought Cepheid variables to the forefront of the astrophysical field and paved the way for modern research into variable stars. In 1956, she proved her immense academic capabilities by becoming the first woman to be promoted to full professor from within Harvard. Payne died on December 7th, 1979 in Cambridge, Massachusetts, leaving behind a legacy in which her groundbreaking discoveries flourished the astrophysical field and cleared the path for other women to follow in her starry footsteps.