In 1879, Williamina “Mina” Fleming was hired as household help for the couple that ran the Harvard College Observatory. An immigrant from Scotland, she had been a teacher before coming to America. But after her husband disappeared, leaving her alone and pregnant, she had no choice but to take any position she could.

And yet, as author Dava Sobel shows in “The Glass Universe: How the Ladies of the Harvard Observatory Took the Measure of the Stars” (Viking), Fleming’s job as a servant to Lizzie and Edward Pickering was a turning point in her life. More than that, it changed the field of astronomy.

Mrs. Pickering recognized Fleming’s talents and recommended that her husband hire her as one of the observatory’s “computers.” These women — often friends of the Pickerings or graduates from the nearby Seven Sisters colleges — had the tedious job of recording measurements from photos their male colleagues took of the stars, preserved on glass slides.

The Harvard observatory was growing, thanks to a bequest from New York City heiress Mary Anna Palmer Draper. After meeting Edward Pickering, and noting the unusual number of women he employed in his lab, she chose him as beneficiary of her late husband’s high-powered telescope, as well as the collection of slides he’d created in an effort to categorize types of stars. Draper agreed to fund the observatory, to the tune of $200 a month (about $60,000 a year in today’s money).

Fleming became fluent in reading the prismatic rays that make up starlight. While her male colleagues spent their evenings in the field, gazing through expensive instruments, she spent her time indoors, looking at slides. By 1890, Pickering’s lab published the Draper Catalogue of Stellar Spectra, a 400-page document that classified the appearance of over 10,000 stars, thanks in large part to Fleming’s dedication.

Pickering acknowledged her contribution in his introduction, but she was denied a byline. As years passed, and she made the discovery of a new star in 1893, Fleming found herself caught between feelings of gratitude and resentment toward Pickering. Although she was doing the work of an astronomer, she was also his assistant.

“You have to put all that is most interesting to you aside, in order to use most of your available time preparing the work of others for publication,” she complained in her journal. She was also paid significantly less than her male colleagues, making $1,500 a year (about $40,000 today) compared to their $2,500 each ($67,000).

Fleming’s work identifying somewhat unusual phenomena earned her international accolades.

Although he refused her a raise, Pickering tried to make it up to Fleming in other ways. He nominated her for the Bruce Medal, which recognized lifelong achievement in the field of astronomy. (She never won.) In 1899, he created the position of curator of astronomical photographs, making Fleming, at the age of 42, the first woman to hold a title at his observatory.

Fleming’s work identifying somewhat unusual phenomena earned her international accolades. Upon her death in 1911, at the age of 54, she had received honorary memberships to both the Royal Astronomical Society and the Société Astronomique de France.

Fleming’s colleague Annie Jump Cannon wrote her obituary, describing her “naturally clear and brilliant mind.” Cannon, who had worked closely with Fleming, was the obvious heir to the job, and Pickering appealed to Harvard’s new president to designate her the observatory’s official curator.

However, the university’s “enlightened age” turned out to have limitations for women beyond just questions of salary. “I always felt that Mrs. Fleming’s position was somewhat anomalous,” the president wrote in response to Pickering’s request. “It would be better not to make a regular practice of treating her successors in the same way.”