The little-known story of the Harvard Observatory's "lady computers"

by Veronika Meduna / 27 January, 2017

Harvard  Observatory data processors at work.

A group of female data processors – or “computers” – who made key discoveries about the stars are chronicled in a new book. 

At first glimpse, it seems that the women pictured on the cover of The Glass Universe are immersed in reading or embroidery. Dressed in high-buttoned Victorian fashion, their hair neatly pinned up, they might have gathered for an afternoon of leisure.

Yet the graphs and charts fastened to the floral wallpaper suggest that theirs is a very different kind of handiwork. They are “computers” – a term used for human data processors long before the invention of machine calculators – and they are scouring photographic glass plates of the night sky, cataloguing stars and charting subtle changes in luminosity, colour and size.

Years later, some of the women would have asteroids and moon craters named after them and fellowships created in their honour, but at this point, they are quietly and meticulously pushing against the glass ceiling of the universe.

Dava Sobel.

The little-known 19th-century story of the “lady computers” at the Harvard Observatory in Cambridge, Massachusetts, and their contributions to astronomy shapes the narrative of Dava Sobel’s latest book. It’s a story the science writer has carried with her for some time, even before she wrote her first bestseller, ­Longitude, more than two decades ago. It’s an account of many intertwining lives that had to wait for its time to come.

“I was never sure that I would be able to find enough information,” she says from her home in East Hampton, New York. “The story seemed amorphous. There were so many women that I wasn’t sure how to approach it.”

Those women include Williamina ­Fleming, a young teacher who emigrated to America from Scotland in 1878 and was forced to look for work, while pregnant, when her husband abandoned her. She was hired as a maid in the household of the Harvard Observatory’s ­director, Edward Pickering, but it soon became clear that she would make a bigger contribution as a computer.

Fleming went on to discover 10 supernovae, or ­exploding stars, more than 200 variable stars and many nebulae. She became the first woman to be appointed curator of the growing ­collection of ­astronomical photographs at the observatory.

Henrietta Swan Leavitt charted the brightness of thousands of variable stars in the Magellanic Clouds, particularly of a group known as Cepheids, which pulsate with a regular rhythm of changing ­luminosity. She discovered a link between the brightness and period of Cepheids – this law became a “standard candle”, a way to measure the size of the cosmos.

Cecilia Payne-Gaposchkin.

Leavitt’s discovery provided ­astronomers with a yardstick to ­determine the distance of far-flung stars and, without it, Edwin Hubble would not have been able to establish that the universe is expanding.

We meet Cecilia Payne-Gaposchkin, who discovered that the sun is made mostly of hydrogen and helium, but was persuaded by her male colleagues not to publish her findings because they contradicted their thinking at the time. Recognition came belatedly and, in 1956, she became Harvard’s first woman astronomy professor.

And Annie Jump Cannon, whose star classification system is still in use. Cannon is Sobel’s favourite protagonist: “She is the best documented, partly because of her diaries and voluminous correspondence. It’s easy to think that you know her.”

Although these names are probably familiar to astronomers, most people, she says, underestimate their ground-breaking achievements.

“They’re called female computers, but really they were astronomers. They were looking at those photographs and making discoveries. Their work and their findings opened up whole new areas of graduate education.”

Annie Jump Cannon.

Their rise through the ranks of a profession dominated by men was aided by Pickering during his more than 40 years as observatory director, from 1877 to 1919. In the US, women had to wait until 1920 for full voting rights, but decades earlier, the observatory had begun employing women to interpret observations made by male astronomers through telescopes each night. In the beginning, most of the women, known as “Pickering’s Harem”, were either married or related to the resident astronomers, but once the first all-female colleges had opened, more young women came looking for work.

This was at a time when photography was transforming astronomy, delivering unprecedented images of the light spectra emitted by different stars. Pickering’s focus was on photometry, or the measurement of the brightness of individual stars, and the scientific challenge to explain why some stars outshone others.

The director showed extraordinary foresight, says Sobel, when he was first approached by Anna Palmer Draper, the wealthy widow of astronomer Henry Draper who had pioneered photographic techniques in astronomy. Pickering quickly recognised her offer to ­sponsor ongoing research in honour of her ­husband’s legacy as a rare opportunity to set up a systematic photographic survey of the night sky, with men working the tele­scopes at night and women analysing the photographic glass plates during the day.

Pickering considered it “unseemly to subject a lady to the fatigue” of telescope observing but thought that women “with a knack for figures could be ­accommodated in the computing room, where they did credit for the profession”.

Pickering had met young women with an interest in science when he was teaching at the ­Massachusetts Institute of Technology (MIT) but his support for women’s education “was certainly not shared by men in general”.


Harvard Observatory in 1888.

For Sobel, the creative challenge of telling the interlacing life stories of the observatory’s women computers seemed at times insurmountable. For at least a year, she went back and forth between trying to approach them as a group and telling the story through the eyes of just one. In the end, the glass plates ­themselves, the luminous record that ­captures a century of stellar signals, became the central character in the book. These images carry the story through the past, allowing each of the women – and Pickering – to take centre stage for a while.

The plates also provide a seductive insight into the future. The observatory’s photographic survey of the universe continued until 1993 and produced half a million glass plates, chronicling tens of millions of stars in both hemispheres. The collection is now being digitised, not only to preserve the historic artefacts but to open up a new field of research based on the unprecedented sequences captured by snapshots of individual stars across a century.

Sobel clearly shares the women ­computers’ gift for painstaking research. Her greatest pleasure, she says, is in getting to know her subjects through their letters and personal diaries. “A project such as this one creates a filter for looking at the world, the science and the social constraints of that period.”

As Sobel shines a light on the women’s lives and science, other artists have also been inspired to produce installations and stage plays based on their stories. Now that the Harvard women are better known, Sobel hopes they will continue to blaze a trail for future generations – just as they did during their own time. Their contributions to the burgeoning field of astronomy forever changed our ­understanding of the stars and our place in the universe.

“The idea of women coming through who were knowledgeable and skilled became acceptable in astronomy more than it did in other fields. When scientists came to Harvard for meetings and saw the large group of women, that had an effect.”

THE GLASS UNIVERSE, by Dava Sobel (Fourth Estate, $36.99)

This article was first published in the January 7, 2017 issue of the New Zealand Listener. Follow the Listener on Twitter, Facebook and sign up to the weekly newsletter.


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