Cecilia Payne: _{Figuring out what stars are made of}

A rising star

Cecilia Helena Payne was born in 1900 in Wendover, England, to an artist mother and a father who was a historian and musician. Her father, Edward John Payne, died when she was just 4 years old. This left her mother, Emma Leonora Helena, to raise Cecilia and two younger children.

Cecilia showed an early interest in science, but it was not considered a suitable field for girls and was not offered at her primary school. She was expelled from her Catholic high school, at least in part for sneaking into the science lab “for a little worship service of my own, adoring the chemical elements” (Payne-Gaposchkin, C.H., 1984). After that, Payne was admitted to St. Paul’s School for girls in London. There, at age 17, she was finally able to study science, writing, “I shall never be lonely again. Now I can think about science!” (Moore, 2020).

Her love of science led Payne to score well on the Cambridge Scholarship exam, which earned her a Mary Eward Scholarship for Natural Sciences at Newnham College at Cambridge. She planned to major in the expected discipline for women – botany. It was rare in those days for women to take courses with men at Cambridge, and Payne had to comply with a university policy that women sit in the front row of class. In later writing about her life, Payne described how her physics professor, Ernest Rutherford,

would gaze at me pointedly…and would begin in his stentorian voice: “Ladies and gentlemen.” All the boys regularly greeted this witticism with thunderous applause [and] stamping with their feet…at every lecture I wished I could sink into the earth. To this day I instinctively take my place as far back as possible in a lecture room. (Payne-Gaposchkin, C.H., 1984) 

Although she started in botany, Payne found her intellectual passion thanks to a lecture she attended by astrophysicist Sir Arther Eddington. He was reporting on his observations during an eclipse on 29 May 1919, on the island of Principe off the coast of West Africa. Eddington’s measurements of light emitted by stars during the eclipse validated Einstein’s General Theory of Relativity by providing evidence that starlight is bent by the Sun’s gravity. Payne was so transfixed by his lecture that she wrote it word-for-word in a notebook and reportedly was bursting with questions afterward. She wrote, “I blurted out that I should like to be an astronomer…he made the reply that was to sustain me through many rebuffs: ‘I can see no insuperable objection’” [Note: “insuperable” means ‘unable to overcome’] (Payne-Gaposchkin, 1984).

Payne changed her major to physics. Her enthusiastic interactions with Eddington gained her access to the library of the Cambridge Observatory, and thus to a wealth of books and journal articles about astronomy. The field of astrophysics flourished during Payne’s undergraduate years at Cambridge, and many leaders in the field were based at the university. This attracted visits from famous colleagues such as Denmark’s Niels Bohr, whose work exploring the structure of atoms would later be the foundation for the atomic bomb (Nobel Prize in Physics, 1922).

It became clear, however, that Payne would not earn a degree. Cambridge University – which expected female students to become classroom teachers – did not officially award degrees to women at that time (University of Cambridge, 2019). She began to contemplate moving to a place that might be more progressive when it came to women’s roles. Payne met the Director of the Harvard University Observatory during his visit to Cambridge. And with Eddington’s recommendation, she won a Newnham College and Pickering Fellowship to conduct research at the Harvard College Observatory.

In 1923, with a $500 stipend promised by the Observatory, this ambitious 23-year-old sailed across the Atlantic to begin work in the United States.

Across the Atlantic

When Cecilia Payne arrived at Harvard University, it was already known for its comprehensive studies of the Sun’s spectrum. In 1895, astrophysicist Edward Charles Pickering (1846–1919) published a way to capture images of stars using a prism over a photographic plate long before digital photography. By the time Payne arrived in 1923, the Observatory had amassed several hundred thousand “spectral” images of stars etched onto glass plates.

Payne was not the first woman at the observatory. In fact, the Observatory had hired women beginning in 1881 in the role of “computers” to classify the star images based on their color and brightness (Wolbach Library). One of those women, Jenka Mohr, published an account of the observatory that describes how the collection of spectral plates “is perhaps our most powerful aid in the plunge into the depths of space by which we hope to know something of the constitution of the sidereal universe” [Note: “sidereal” means ‘relating to stars’] (Mohr, 1932).

But the “computers” were compensated at the level of unskilled workers, despite their aptitude for creating spectral plates. Some of the Harvard Observatory women made substantial contributions to the field. One of these was Annie Jump, who created a 7-category classification scheme for the spectra of the thousands of star images (Perkowitz, 2022). Still, none of these women were considered researchers or collaborators, despite their aptitudes and insights. In other words, Payne had landed in an environment where women were welcome, but only at the lower levels of the academic setting.

Probing the spectra of stars

When Payne arrived, the Harvard Observatory was building its PhD program in Astronomy, for which she was the first-ever candidate, despite being a woman. Payne – like many doctoral students – became deeply engaged in her research. Reflecting later on her graduate school years, Payne says, “There followed months, almost a year as I remember, of utter bewilderment. Often I was in a state of exhaustion and despair, working all day and late into the night” (Payne-Gaposchkin, C.H., 1984).

As a graduate student, Payne made a major discovery about stars using spectral images (showing the brightness of starlight separated into the colors of the spectrum). The prevailing theory of the time, grounded in the work of geochemist Frank Wigglesworth Clarke (1847–1931), was that the atmospheres of the Sun and other stars were similar in composition to Earth’s crust. While that sounds improbable now, Clarke had established that each element in Earth’s crust has a certain light absorption spectrum (Clarke, 1889). Seeing similar spectral lines of the Sun, astrophysicists concluded that it was made up of a similar suite of elements, such as iron, calcium, carbon, and silicon.

However, Payne was influenced by Indian astrophysicist Meghnad Saha (1893–1956) after he visited Harvard in 1920. Saha had developed an equation that related spectral lines, which are distinct for each element, to the state of an atom in terms of its electrons (see our module Atomic Theory I). Payne calculated the relative amounts of 18 elements based on the Sun’s spectral lines and found, contrary to Clarke’s theory, that hydrogen and helium were the most common by far. Her research showed hydrogen in the Sun’s atmosphere to be a million times greater than in Earth’s crust (see our module History of Earth’s Atmosphere I).

In overturning Clarke’s ideas, Payne also proved that the colors of stars derived from their temperature, not their chemical composition. This discovery would forever change the scientific understanding of stars! Danish astronomer Ejnar Hertzsprung (1873–1967) had earlier plotted the color of stars against their brightness to demonstrate the relationship, and Payne’s work refined the x-axis to temperature (Figure 3). Her system for decoding the light spectra of stars permanently changed how stars’ spectra are interpreted. However, she did not receive credit for the pivotal discovery; rather, her advisor, Russell, would later claim credit, thus garnering his name on the Hertzsprung-Russell diagram.

The glass ceiling

On 1 January 1925, when Cecilia Helena Payne submitted her dissertation, “Stellar Atmospheres: A Contribution to the Observational Study of High Temperature in the Reversing Layer of Stars,” she did not recognize the significance of her results. Indeed, she wrote,

The enormous abundances derived for those elements in the stellar atmosphere are almost certainly not real. Probably the result may be considered, for hydrogen, as another aspect of its abnormal behaviour … and helium … possibly deviates for similar reasons (Wayman, 2002).

Payne’s confidence in her results had been eroded by conversations with her advisor, who was one of the most prominent astrophysicists of the time, Princeton University’s Henry Norris Russell (1877–1957). He was convinced of the prevailing theory that the Sun had the same composition as Earth’s crust, and so he deemed her results “clearly impossible” after reviewing her draft thesis (Moore, 2020). Because of Russell’s skepticism, Payne did not share her most significant results.

Then, the Chair of Physics at Harvard University rejected her dissertation because she was a woman. Instead, her degree was awarded by Radcliffe College, the sister school to Harvard. Still, she was the first person to earn an Astronomy PhD at Harvard or Radcliffe, regardless of her gender (Weintrab, 2020)! Four years later, her advisor, Russell, published a paper that supported Payne’s conclusion about the dominance of hydrogen in the stars. However, he included just a single reference to Payne’s work (Russell, 1929).

After completing her PhD, Payne naturally considered a position as a professor, but found that Harvard was reluctant to hire a woman. Then-President Abbott Lawrence Lowell, when approached by the Observatory’s Director Shapley about hiring Payne, reportedly responded that “Miss Payne should never have a position in the University as long as he was alive” (Moore, 2020).

Payne, therefore, continued to conduct her research at the Harvard Observatory from 1927–1938 as a “technical assistant,” much like the women “computers.” Even though she taught graduate classes, she did not carry the title of Professor or even Instructor. She was paid very little and is said to have pawned her jewelry to make ends meet. She considered leaving altogether (Weintrab, 2020).

Still, Payne stayed on and became part of the Observatory community (Figure 4). Despite the frustrations and professional barriers, Payne continued to be productive. She published her second book, Stars of High Luminosity, in 1930 – sharing her work on several million observations of the brightest stars.

Payne’s personal life also evolved during that decade. When she visited Europe in 1933, she met an exiled Russian astronomer, Sergei Gaposchkin, at a German Astronomical Society meeting. She and Gaposchkin were married a year later. During their marriage, they raised three children and coauthored several hundred astronomy papers and a handful of books together. Indeed, it’s said the children were largely raised at the Harvard Observatory among the telescopes and data.

Finally landing

In 1956, when she was 56 years old, Payne was finally appointed a Full Professor in Harvard’s Faculty of Arts and Sciences, and later as Chair of the Astronomy Department by the new director of the observatory, Donald Menzel, who had started in 1954. On 21 June 1956, the New York Times printed, “Harvard University announced today the appointment of Dr. Cecilia Payne-Gaposchkin as Professor of Astronomy. She is the first woman to attain full professorship at Harvard through regular faculty promotion” (Moore, 2020).

A decade after her academic appointment, Payne retired. At 66 years old, she had only gotten to enjoy 10 years of working with the status of Full Professor. Still, she was awarded Emeritus status and continued to write and edit books published by the Harvard Astrophysical Observatory for an additional 20 years. Her passion for research remained. However, she was never as enthusiastic about the required teaching. In her autobiography, Payne wrote,

I think that my distaste [for teaching] stems from the inherent conflict between teaching and research. A lecturer must pose as knowing everything about his subject (and some even seem to believe that they do); in research one must continually remind oneself that one knows little or nothing (Payne-Gaposchkin, 1984).

Renowned astrophysicist Joan Feynman (1927–2020), who made discoveries about solar wind and magnetospheres that affect spacecraft and life on Earth, was motivated by Payne’s work. Feynman describes how she was initially discouraged from science by her grandmother, who in 1935 told her, “Women can’t do science because their brains can’t understand enough of it.” But reading an astronomy book six years later shook her of that unfortunate notion when she came across a graph of stellar absorptions with a reference to Payne’s Stellar Atmospheres book. At that point, Feynman wrote, “It was scientific proof that a woman was capable of writing a book that, in turn, was quoted in a text. The secret was out, you see” (Hirschberg, 2002).

A life of achievements

Payne (Figure 5) spent the majority of her career in positions with lower status and pay than she merited. Today, the caliber of her work would likely garner her election to the National Academy of Sciences, which recognizes scientists who make outstanding contributions to research. But, despite the barriers, Payne continued to research and write about the subject she loved – astrophysics. She died at age 79 not long before her autobiography was published (Payne-Gaposchkin, C.H., 1984).

Payne’s contributions to studying the universe fundamentally changed how astronomers interpret the light from stars. Interpretation of the Hertzsprung Russell diagram was overhauled thanks to her work. It still serves as the reference for students and researchers in astronomy to classify types of stars by their spectral colors. Her discovery that hydrogen is the most abundant element of the Sun is key to today’s understanding of hydrogen as a building block of our universe.

Among her many accomplishments, Payne was elected to the Royal Astronomical Society in 1923 while still a university student, and later to the American Philosophical Society (1936) and the American Academy of Arts and Sciences (1943). She was the first recipient of the Annie J. Cannon Award in Astronomy (1934) and later received a Radcliffe College Award of Merit (1952); a Rittenhouse Astronomical Society medal (1961); and the Henry Norris Russell Lectureship of the American Astronomical Society (1976). In addition to her Professor Emerita of Harvard University, Payne was granted Honorary Degrees from Colby College, Rutgers University, Smith College, Western College, Wilson College, and the Women’s Medical College of Pennsylvania. Many things were named after her, including an asteroid, a volcano on Venus, a telescope in South Africa, an Institute of Physics Prize, and the American Physical Society’s Doctoral Dissertation Award in Astrophysics!

In her acceptance speech for the Norris Russell Prize when she was 76 years old, Cecilia Payne said,

The reward of the young scientist is the emotional thrill of being the first person in the history of the world to see something or understand something. Nothing can compare with that experience…The reward of the old scientist is the sense of having seen a vague sketch grow into a masterly landscape.