Annie Walker: The astronomer with an asteroid, but no known photographs

Annie Walker was 15 years old when, in 1879, she started working as a “computer” at the Cambridge University Observatory. This involved hours and hours of routine, tedious, and intense calculations that astronomers disliked, but which, at the time, were essential for accurately measuring the positions of stars and planets. Calculators were usually boys, but observatories sometimes hired girls, as was the case with Walker, although her male colleagues had exclusive use of the telescopes. She managed to escape this humble status to become a senior observer in the Victorian era, documenting the positions of 1,585 stars individually and several thousand more collaboratively. In April, the International Astronomical Union (IAU) named an asteroid in the Themis group in her honor: (5400) Anniewalker = 1989 CM.

Walker’s name has escaped the shadows of oblivion and returned to the outer Main Belt following research by Mark Hurn, librarian at the Institute of Astronomy at the University of Cambridge, and historian Roger Hutchins. The two have been charting Walker’s career for over a decade and have just published their findings in the journal The Antiquarian Astronomer. “We clearly establish that she was, if not Britain’s first professional female astronomer, then certainly the second, behind only Caroline Herschel,” Hurn says via video link. In 1895, Walker was paid a salary of 90 pounds, making her the highest-paid woman in British astronomy at the time, far above all other computers.

Her story has something of a cosmic twist. When Walker joined the Cambridge Observatory, it was headed by astronomer John Couch Adams, who predicted the existence of the planet Neptune, and was very much in favor of women’s emancipation and education, so he had no problem hiring Walker. The main assistant — it was beneath the director’s dignity to dedicate himself to observation at the time, as they tended to be more theoretical — was astronomer Andrew Graham, an older man whose eyesight had clearly deteriorated over his many years observing the heavens. Furthermore, the type of observing they were doing required two people, and they needed to train someone to use the telescopes. And Annie was there. “She was obviously a clever girl. In addition to computing, she helped Adams sort through some of [Isaac] Newton’s papers,” Hurn says.

Walker moved in with the Grahams, who lived in the observatory, with the telescopes next to the living room. For 25 years, she spent entire nights, hours and hours in darkness, staring at the sky, training her eyes to detect very subtle differences in the brightness of stars or their position, pointing, measuring, comparing, and taking notes. It was very intense work, but she was still a computer, and when day dawned, she would return to her calculations.

It was also the case that all three — Adams, Graham, and Walker — were religious dissenters, something quite unusual in Cambridge at the time. “They were Protestants, with quite radical convictions, not part of the Church of England or the establishment, so in many ways they were quite separate from the university itself,” explains Hurn. In this environment, Walker, the daughter of a corn miller, became the observatory’s principal observer.

Mapping the night sky

Many of her observations were recorded in The Cambridge Zone Catalogue, part of the first international attempt to map the night sky to the same standards — down to the 9th magnitude — that the German Astronomical Society had set in motion in 1872. The catalog was published in 1897 in Leipzig. “The portion assigned to this observatory, zone 25° to 30°, containing the locations of 14,464 stars, the result of some 47,570 observations, has just been published. The completion […] marks an epoch in its history. I wish to record my sincere thanks for the skill, diligence, and enthusiasm with which Mr. Graham has applied himself to so important a task. He has had the invaluable assistance of Miss Walker, whose industry and care, both in observations and reductions, have contributed significantly to the success of the undertaking,” Adams wrote.

But Walker continued to observe up to three times as many stars that — due to climate or time of year — had not previously been well observed. These observations, some 4,800 corresponding to 1,585 stars, were published in the 1920s by the famous astronomer Arthur Eddington. The appendix entitled “Revisions Made by Miss Walker Between the Years 1896 and 1899” constituted 10% of the total publication and was “exclusively hers, although she clearly contributed to a large part of other publications that came out of Cambridge at that time,” says Hurn.

When the librarian learned of Walker’s story, he contacted the Cambridge team of the European Space Agency’s Gaia mission, which is mapping the billion stars that illuminate the Milky Way, “the same kind of work Annie was doing,” he notes. Like the rest of the astronomical community, the team was unaware of Walker’s story, and its director, Gerry Gilmore, proposed to the International Astronomical Union that an asteroid be named in her honor. A few months ago, Walker’s name reached the skies.

“The asteroid is really cool — it has a low number, which means it was one of the first discovered and at the top of the list. When you research historical figures, you start to feel something for them; you think you know them. So I was very happy, but I’m sad that she never received recognition during her lifetime,” Hurn says.

Adams died in 1892, and the new director, Robert Ball, an eminent astronomer, didn’t share Adams’s political views at all and made it very clear that Annie’s situation wasn’t to his liking. When Graham retired, Walker thought she should take the post, but Ball gave it to a younger man she had trained. “I think it was too humiliating for her. In 1903, at the age of 40, she resigned and emigrated to Australia. She never worked as an astronomer again, although in an electoral register there we find that for a couple of years she described herself as such. It’s very sad; she just disappears at that stage of her life. We don’t have any photographs of her,” explains Hurn.

Hutchins and Hurn have been searching for a photo of Walker for years, but haven’t found one, either in the library’s collection or by contacting descendants in Australia. “We’re hoping the religious aspect will reveal something. It’s possible she attended services that were photographed, weddings, funerals... That’s where we’re looking. Having a photograph of a person makes a huge difference. It’s for their memory; we really need to find one. But I haven’t given up hope; it’s quite possible we’ll find it one day,” the librarian adds. Walker died in Melbourne in 1940.

Hurn concludes the interview with a lighter touch. Walker reportedly gave a talk about the Moon at a church in a village near Cambridge and told a few jokes.

— Could you repeat them for me?

— They’re not very funny. One of them was that you didn’t need to learn the names of the craters on the far side of the Moon because you couldn’t see them (laughs). But I loved receiving this information, a little snippet from Annie. It made it so much more real.

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