Cecilia Payne Gaposchkin
Cecilia Payne Gaposchkin was an English-American astronomer who was the first to discover that the sun was composed primarily of hydrogen, but, due to pressure from her male colleagues, she was forced to make a less definitive statement in her thesis and is often not credited with the finding at all.
Gaposchkin was born in Wendover, England and was an avid student. Unfortunately, no one (including her own mother) seemed to care. When it was time for college, Gapsochkin was on her own and won a scholarship in 1919 to go study at Cambridge. There she studied botany, physics, and chemistry.
While at Cambridge she attended a lecture by Arthur Eddington on his work in Principle (an island off of the west coast of Africa) where he observed and photographed the stars near an eclipse as a test of Einstein’s theory of relativity. This sparked her interest in astronomy, but Cambridge would not allow to her to change her course of study from physics, and later though she completed her studies, would not grant her a degree. (Cambridge didn’t grant degrees to women until 1948).
After meeting Harlow Shapley, the Director of the Harvard College Observatory, who had just begun a graduate program in astronomy, Cecilia Payne left England for the United States in 1923. This was made possible by a fellowship to encourage women to study at the Observatory. (The first student was Adelaide Ames in 1922).
Shapley persuaded Cecilia Payne to write a doctoral dissertation, and so in 1925 she became the first person to earn a Ph.D. in astronomy from Harvard for her thesis: “Stellar Atmospheres, A Contribution to the Observational Study of High Temperature in the Reversing Layers of Stars”. Astronomer Otto Struve characterized it as”undoubtedly the most brilliant Ph.D. thesis ever written in astronomy.”
By applying the ionization theory developed by Indian physicist Meghnad Saha she was able to accurately relate the spectral classes of stars to their actual temperatures and that the variation among stars was due to differing amounts of ionization at different temperatures, and not due to different amounts of elements in stars as previously believed. She correctly suggested that silicon, carbon, and other common metals seen in the Sun were found in about the same relative amounts as on Earth, but that helium and particularly hydrogen were vastly more abundant. Her thesis established that hydrogen was the overwhelming constituent of the stars. When her dissertation was reviewed, she was dissuaded by Henry Norris Russell from concluding that the composition of the Sun is different from the Earth, which was the accepted wisdom at the time. However, Russell changed his mind four years later when he published his own paper utilizing Gaposchkin’s findings and is often credited with her work instead of Gapsochkin herself.
After her doctorate, Gaposchkin then studied stars of high luminosity in order to understand the structure of the Milky Way and made over 1,250,000 observations with her assistants on variable stars. Her observations and analysis, with her husband, of variable stars laid the basis for all subsequent work on them.
Gaposchkin remained scientifically active throughout her life, spending her entire academic career at Harvard. At first, she had no official position, merely serving as a technical assistant to Shapley from 1927 to 1938. At one point she considered leaving Harvard because of her low status and poor salary. However, Shapley made efforts to improve her position, and in 1938 she was given the title of “Astronomer”. She later asked to have this title changed to Phillips Astronomer. None of the courses she taught at Harvard were recorded in the catalogue until 1945.
When Donald Menzel became Director of the Harvard College Observatory in 1954, he tried to improve her appointment, and in 1956 she became the first woman to be promoted to full professor. Later, with her appointment to the Chair of the Department of Astronomy, she also became the first woman to head a department at Harvard.
Sadly today students may learn who discovered gravity and revolution, but when told that the universe is mostly composed of hydrogen no one knows that it was Cecilia Payne Gaposchkin who made that discovery.
Finally, I leave you with this:
For more information:
Payne-Gaposchkin, Cecilia. Cecelia Payne-Gaposchkin: An Autobiography and Other Recollections. Cambridge: Cambridge University Press, 1996.