Women You Should Know: Cecilia Payne Gaposchkin

Women You Should Know: Cecilia Helena Payne Gaposchkin
[Meredith Sell]

One hundred years ago, astronomers looked at the cosmos quite differently from the way they do today. They had observatories and telescopes and theories, Einstein’s theory of general relativity was still (relatively) new in the science community, and astronomers as usual were trying to figure out the stars.

Today, we know hydrogen as the universe’s most common element. But, not then. The scientific community was convinced that stars were more similar to earth than they were different. They believed the elements that made up earth (silicon, aluminum, iron, etc.) were the same as those that composed the stars — and in, if not identical, then at least similar ratios. Stars were just hotter versions of planet earth.

Enter Cecilia Helena Payne.

Born in Wendover, England, in 1900, Cecilia had developed a passion for scientific research and discovery early in life. Her first interests were in botany and, as a child, she dreamed of becoming a paleobotanist — a scientist who studies fossilized plants. In a 1968 interview with science historian Owen Gingerich, she recalled being invited as a schoolgirl to visit the experimental breeding garden of William Bateson (an English geneticist) in Wimbledon, England, because of her interest in biology.

“I remarked to him what I thought then, and still think, that doing research must be the most wonderful thing in the world,” she said, “and he snapped at me that it wasn’t wonderful at all, it was tedious, disheartening, annoying and anyhow you didn’t need an experimental garden to do research. You could do research sitting in a train looking at other people with you or walking down the street, looking at the people and so forth … He almost reduced me to tears.”

This encounter did not turn Cecilia away from a life of research. In fact, her scientific career involved plenty of research involving neither experimental garden nor observation of people.

As a first-year student at Cambridge (England) in 1919, Cecilia studied science, still pursuing botany. Then, she sat in on a special lecture by Sir Arthur Eddington. He was sharing about a recent expedition to the island of Principe, off the western coast of Africa, where he had made observations of a solar eclipse that confirmed Einstein’s theory of general relativity.

Cecilia was so enthralled by his talk that afterward, she went home and wrote it down word for word.

She couldn’t switch her study tract at Cambridge to astronomy, so she contented herself to attend as many astronomy classes as she could, do some research for Eddington (which led to her first publication), read as much as possible in the Cambridge Observatory’s library, and clean up a small observatory at Newnham College (Cambridge) that had fallen into disuse and disrepair so she could use it for her own observations.

A Cambridge Ph.D. student Cecilia identified as Comrie helped her in the observatory and gave her a book on variable stars and, when the newly appointed Director of the Harvard College Observatory, Harlow Shapley, came to London to lecture at the British Astronomical Association, Comrie invited Cecilia to attend.

“I was completely fascinated because for the first time I had a vision of the way in which astronomy conducts observations,” she said of the talk.

After the lecture, she approached Shapley and told him she wanted to work for him. He gave a light-hearted word of encouragement and, months later, Cecilia was on a ship crossing the Atlantic, going to the United States for the first time for a research fellowship with the Harvard College Observatory.

She was going to study the stars.

Harvard College Observatory was home to the world’s largest collection of stellar spectra on photographic plates. These spectra displayed the light of a particular star as recorded by a spectrograph. The spectrograph broke the light into the full spectrum of visible color, from red to violet, revealing black “absorption lines” where a particular wavelength of light was missing.

Starting in the 1880s, Harvard astronomers had classified stars into seven types based on their absorption lines. But no one knew what caused the differences in starlight. In 1859, German scientists, Gustav Kirchoff and Robert Bunsen, had found that each element had signature absorption lines, but because the ruling assumption in the scientific community was that the earth’s elemental makeup matched that of other celestial bodies and stellar spectra didn’t match that assumption, the astronomical community was left scratching their heads.

Cecilia arrived in Cambridge, Massachusetts, in the fall of 1923 and before long, was headfirst in stellar spectra. Before she’d arrived, another female astronomer, Annie Jump Cannon, had sorted much of the stellar spectra collection into the seven known classes. Now Cecilia started questioning the cause of their distinctions.

Rather than trying to find what ratios earth’s elements would produce those same absorption lines, she applied Indian physicist Meghnad Saha’s recent theory of ionization to the question.

After two years of work, at age 25, she published her thesis, “Stellar Atmospheres”, in which she demonstrated that the variation in stellar spectra was due mainly to different ionization states of atoms (which directly correspond to surface temperature) and then charted out estimated amounts of elements that comprised the stars.

Here’s where things got messy:

Her work had found that all stars have similar elemental makeups, with 99% comprised of hydrogen and helium. But because the accepted belief in the scientific community was that stars had a makeup relatively similar to that of earth, when Cecilia’s advisor and mentor Harlow Shapley sent her thesis (before publication) to astronomer Henry Norris Russell, Russell responded with mostly positive comments, except:

“There remains one very much more serious discrepancy, namely, that for hydrogen, helium and oxygen. Here I am convinced that there is something seriously wrong with the present theory. It is clearly impossible that hydrogen should be a million times more abundant than the metals….”

With this feedback, Cecilia added a note to her thesis, undercutting the strength of her claim and essentially saying that her discovery regarding the abundance of helium and hydrogen was in error. Only four years later, Russell published a paper of his own where he demonstrated the same abundance of those two elements, which we now accept as fact without question.

As a result of her thesis, Cecilia received the first Ph.D. in astronomy from Radcliffe College (a women’s institution associated with Harvard; Harvard did not grant doctoral degrees to women at that time). In Astronomy of the 20th Century (1962), astronomers Otto Struve and Velta Zeberg said Cecilia’s thesis was “undoubtedly the most brilliant Ph.D. thesis ever written in astronomy.”

Cecilia spent the rest of her career at Harvard, working for many years as “technical assistant” to Shapley, but doing much more independent research than mere assisting.

In 1933, Cecilia traveled to eastern Europe to interface with various astronomers. In Germany, she met Sergei Gaposchkin, a Russian astronomer who was unwelcome in the Soviet Union because of his politics and unwanted in Nazi Germany because of his race. She found him a position at Harvard Observatory and helped him come to America, marrying him soon after and collaborating with him on astronomical research while building a family together.

Cecilia taught at Harvard for many years without title of professor or mention of her courses in the college catalog due to her sex. It wasn’t until 1956, after three decades at the institution, that she was appointed as full professor. She was made chair of Harvard’s astronomy department the same year — the first woman to chair a department at Harvard.

In 1968, at nearly 68 years old, Cecilia reflected on her arrival to Harvard with little hint of resentment to the place:

“Being free, for the first time, to do astronomy just as much as I wanted when I never had been before was intoxicating, because even though I had done these little bits of research at Cambridge [England] and there had always been lectures to go to and things to study and one had to keep up with one’s studies…. For a bit, [at Harvard] I almost worked night and day without stopping. It was marvelous.”

We like this video ^ about our girl, Cecilia (even though we didn’t make it).

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