CNJ+ February 2024

CECILIA PAYNE- GAPOSCHKIN A Woman of the Stars! By Pam Teel

Cecilia Payne-Gaposchkin, born Cecilia Hel ena Payne (May 1900 – December 7, 1979) was a British-born American astronomer and astro physicist who proposed in her 1925 doctoral the sis that stars were composed primarily of hydro gen and helium. Her groundbreaking conclusion was initially rejected because it contradicted the scientific wisdom of the time, which held that there were no significant elemental differences between the Sun and Earth. Independent obser vations eventually proved she was correct. Her work on the nature of variable stars was founda tional to modern astrophysics. Payne was one of three children born in Buck inghamshire, England, to Prussian-born Emma Leonora Helena (née Pertz) and Edward John Payne, a London barrister, historian, and musi cian. Payne’s father died when she was four years old, forcing her mother to raise the family on her own. Payne began her education at a private school. When she was twelve, her mother moved the family to London where Cecilia attended St

actual temperatures by applying Indian physicist Meghnad Saha’s ionization theory. She showed that the great variation in stellar absorption lines was due to differing amounts of ionization at different temperatures, not to different amounts of elements. She found that silicon, carbon, and other common metals seen in the Sun’s spectrum were present in about the same relative amounts as on Earth, in agreement with the accepted be lief of the time, which held that the stars had ap proximately the same elemental composition as the Earth. However, she found that helium and particularly hydrogen were vastly more abun dant (for hydrogen, by a factor of about one mil lion). Her thesis concluded that hydrogen was the overwhelming constituent of stars, making it the most abundant element in the Universe. However, when Payne’s dissertation was re viewed, astronomer Henry Norris Russell dis suaded her from concluding that the compo sition of the Sun was predominantly hydrogen because it would contradict the scientific con sensus of his 1914 article that the elemental com position of the Sun and the Earth were similar.

Mary’s College in Paddington. There, she was unable to study much in the field of mathematics or science merely because she was a female. (Women were highly discouraged from studying these fields.) In 1918 she transferred to an all-girls school where she was urged to pursue a music career but pre ferred to focus on science. Her mother refused to pay for her to go to college. The following year she won a scholarship that paid all her expenses at Newnham College, Cambridge University, where she focused on studying botany, physics, and chemistry. Her interest in astronomy began after she attended a lecture by Arthur Eddington on his 1919 expedition to the island of Príncipe in the Gulf of Guinea off the west coast of Africa to observe and photograph the stars near a solar eclipse as a test of Albert Einstein’s general theory of relativity. She said of the lecture: “The result was a complete transformation of my world picture.” She completed her studies but was not awarded a degree because she was a female. Cambridge did not grant degrees to women until 1948. Payne realized that her only career option in the U.K. was to become a teacher, so she looked for grants that would enable her to move to the Unit ed States. In 1923, she was introduced to the Director of the Harvard College Observatory, Harlow Shapely. He had just established a graduate program in astronomy, making it possible for women, with the aid of a fellowship, to study at the observatory. Payne became the second female student to ben efit from the fellowship. She was persuaded by Shapely to write a doctoral dissertation, and in 1925, she became the first person to earn a Ph.D. in Astronomy from Radcliffe College of Harvard University. Payne was able to accurately relate the spectral classes of stars to their

A few years later, astronomer Otto Struve described her work as “the most brilliant Ph.D. thesis ever written in astronomy”. Henry Norris Russell also realized that Payne was correct in her findings when he derived the same results by different means. In 1929, four years after Payne’s findings, Rus sell published his works in a paper that briefly acknowledged Payne’s ear lier work and discovery, including the mention that, “the most important previous determination of the abundance of the elements by astrophysical means is that by Miss Payne.” Nevertheless, he was generally credited for the conclusions she had reached four years earlier. After her doctorate, Payne studied stars of high luminosity to understand the structure of the Milky Way. Later she surveyed all the stars brighter than the tenth magnitude. She then studied variable stars, making over 1,250,000 observations with her assistants. This work later was extended to the Magel lanic Clouds, adding a further 2,000,000 observations of variable stars. These data were used to determine the paths of stellar evolution. She published her conclusions in her second book, The Stars of High Luminosity in 1930. Her observations and analysis of variable stars, along with her husband Sergei Gaposchkins analysis, laid the basis for all subsequent work on such objects. Payne-Gaposchkin remained scientifically active throughout her life, spending her entire academic career at Harvard. When she began, women were barred from becoming professors at Harvard, so she spent years do ing less prestigious, low-paid research jobs. Nevertheless, her work resulted in several published books, including T he Stars of High Luminosity (1930), Variable Stars (1938), and Variable Stars and Galactic Structure (1954). Continued on page 22

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