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‘Women computers’ often couldn’t use Harvard’s telescope. They changed astronomy anyway

Photos of “women computers” Williamina Fleming (top left) and Henrietta Swan Leavitt.Craig F. Walker/Globe Staff

In the 1800s, it was unseemly for women to search the night sky with male astronomers. Instead, they worked in the Harvard College Observatory as assistants.

Between 1875 and 1927, more than 80 women were employed at the observatory as so-called “women computers,” that is, women who performed scientific and mathematical calculations by hand.

For 25 to 30 cents an hour, their task was the meticulous study and care of black and white astronomical photographs of the night skies. In most images, the stars were tiny black dots on a white background.

Day in and day out, the women explored the cosmos without looking through a telescope. It was painstaking work. Using a simple magnifying glass, they studied the stars, work that eventually led to discovering their composition. Staring at these stellar clusters, chemically captured on glass plates, helped them gauge immense distances in space and measure the brightness of stars.

Like the African-American women of the US space program depicted in “Hidden Figures,” they remained behind the scenes, holding stars in their hands.


Glass plates helped “women computers” gauge immense distances in space and measure the brightness of stars.Craig F. Walker/Globe Staff

“Not only did these glass plates change the study of science in general,” said Lindsay Smith Zrull, curator of astronomical photographs at the Harvard-Smithsonian Center for Astrophysics in Cambridge, “they changed who could do science.”

Inside the archive, center staffers have been digitizing the collection of more than 500,000 stellar glass plates. There are three floors of metal closets that contain stacks of these images, spanning more than a century of sky gazing. But in the past year, the curator also unearthed 118 boxes of notes from the women computers.

Most of these boxes sat untouched in a depository for decades.

Now, in partnership with the Smithsonian Transcription Center, volunteers around the world are transcribing scribbled logbooks and research notes from the women computers as quickly as they’re scanned and uploaded.


The effort is called Project Phaedra, which stands for Preserving Harvard’s Early Data and Research in Astronomy. Phaedra is a character in Greek mythology. Her name was derived from the Greek word phaidros, which meant “bright,” said Daina Bouquin, head librarian at the John G. Wolbach Library in the Harvard-Smithsonian Center for Astrophysics.

“It’s really important to bring to light what these women did,” said Katie Frey, assistant head and digital technologies development librarian at the Wolbach Library. “They made groundbreaking discoveries in astronomy. They really changed the course of astronomy.”

Photos of women computers at Harvard Smithsonian Center for Astrophysics.Craig F. Walker/Globe Staff

Newspaper articles from the time considered the women a novelty at best with headlines such as: “Brainy Boston Women Learn Sky’s Profoundest Secrets.” But Edward Pickering, the director of the Harvard College Observatory in the late 1800s, knew better. It was his mission to hire an entire corps of women computers to conduct scientific work.

“Much of the funding [for the original glass plate work] came from women, most of the work was done by women,” Smith Zrull said. “Which made it a very unusual collection, unusual workplace back in the late 1800s, early 1900s.”

One of the earliest women computers, Annie Jump Cannon, kept detailed letters and scrapbooks of the time with prolific annotations. She classified hundreds of thousands of stars. And of that first generation of women, she was the only one allowed to use Harvard’s Great Refractor telescope.

Williamina Fleming emigrated to the United States with her husband from Scotland in December 1878. He abandoned her when she was pregnant. She began working as a housemaid under Pickering. In Scotland, she’d been a school teacher and had a talent for numbers. Fleming soon became the head of the “computers.”


She discovered the Horsehead Nebula, a dark nebula in the constellation Orion, in 1888.

“In 1899, [Fleming] was the first curator of astronomical photographs,” said Maria McEachern, a reference librarian at the Wolbach Library. “And the first woman at Harvard to attain a professional position.”

Henrietta Swan Leavitt discovered how to measure stellar distances by focusing on variable stars (that is, stars whose brightness fluctuates) in the large and small Magellanic Clouds, two dwarf galaxies. She discovered about 2,400 of them, plotting how light from the same star changed over time.

A 1934 glass galaxy count plate negative at Harvard Smithsonian Center for Astrophysics.Craig F. Walker/Globe Staff

“How do you find a variable star?” Smith Zrull said. “What you have to do is look at every single plate in the same region of the sky and compare each and every single one of them from different dates.”

Perhaps the best known woman in the field was Cecilia Payne, a scholar from England and a woman computer who discovered the composition of the stars, according to Dava Sobel, author of “The Glass Universe: How the Ladies of the Harvard Observatory Took the Measure of the Stars.”

The University of Cambridge would not accept a female PhD student. She later came to the Harvard College Observatory and, in 1925, earned a PhD in astronomy for her work. In the 1960s, Otto Struve, at one point the director of Yerkes Observatory in Chicago, called her dissertation on stellar atmospheres “undoubtedly the most brilliant PhD thesis ever written in astronomy.”


“Regardless of whether or not these women made discoveries, research is research,” said Bouquin. “You shouldn’t just forget about it because it got old. This was cutting-edge science at one point.”

In photographs the women computers sit together in long dresses, posing for the cameras or holding hands outside the observatory where many of them spent much of their lives.

Fleming was known to get weekly massages for the shoulder pain she developed from leaning over the glass plates for hours at a time. In 1900, she wrote about it in a diary she kept that ended up in a time capsule that was buried to mark the century. In her diary, she also complained about her pay and wrote of her responsibilities as a single mother.

Somewhere along the line, the women computers’ notes on glass plates, logbooks, and achievements disappeared into obscurity.

Until now.

“I am not an astronomer,” Smith Zrull said. “I am just very much inspired by women — especially women who overcame all sorts of obstacles to make a place in their field or in the world. What makes me most passionate about this is that we’re giving them the credit they always deserved.”

A group of women computers, directed by Williamina Fleming, back center standing.Harvard College Observatory, circa 1890

Cristela Guerra can be reached at