Dava Sobel’s new book, “The Glass Universe,” tells the story of a group of women at Harvard who conducted breakthrough research on the nature of stars and the universe. Sobel appears Thursday, Dec. 15, at Town Hall Seattle.

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Imagine a vast library containing half a million items. But instead of books, envision glass plates with silver gelatin emulsion photographs of stars. The collection was begun in the 19th century and assembled during many decades, primarily at Harvard College Observatory, but also in South America, South Africa and numerous other locations by both professional and amateur astronomers. A fabulous story in itself, this “glass universe,” notes Dava Sobel, an award-winning science writer and author of “Longitude,” also contains the fascinating history of the many women who worked as calculators — or human “computers” — interpreting images made by the men who took these pictures.

In “The Glass Universe: How the Ladies of the Harvard Observatory Took the Measure of the Stars” (Viking, 336 pp., $30), Sobel begins her story in 1882, at a dinner party hosted by Anna Draper in New York for 40 members of the National Academy of Sciences. It would prove to be one of two prime catalysts for the photographic project. Her husband, Dr. Henry Draper, had won acclaim for achievements in stellar photography. When he died suddenly soon after the Academy dinner, one of her guests, Harvard Professor Edward Pickering, offered to help continue the doctor’s research measuring stellar spectra, “the telltale patterns of lines [in photographs] … that hinted at the stars’ constituent elements.”

Because the observatory received no funding from the college, part of Pickering’s job as director was to solicit contributions. He wrote Anna Draper in 1885, proposing a long-term study with a new instrument combining a spectroscope and telescope and using a camera lens. The next year, he sent sample images. She replied that she would be willing to help fund a photographic catalog of stellar spectra taken on glass plates. It would be called the Henry Draper Memorial. She also donated a telescope and the cost of a building to house it, the first of many generous contributions.

Author appearance

Dava Sobel

The author of “The Glass Universe” will appear at 7:30 p.m. Thursday, Sept. 15, at Town Hall Seattle, 1119 Eighth Ave. Tickets are $5 at townhallseattle.org and at the door. Information: 206-652-4255.

These funds triggered research “into the stars’ physical nature.” New “computers” were hired, some of whom continued calculating “locations and orbital dynamics of heavenly bodies” while others learned to read glass plates. Eventually, a photographic collection, the Henry Draper Catalog, would be the first in history to specify spectrum type as well as position and brightness of thousands of stars.

The scientists’ wives, sisters and daughters were joined by recent graduates of women’s colleges. Sobel features their lives and achievements alongside work that revealed information about stars’ temperature, motion and chemical composition.

Annie Jump Cannon, for example, developed a classification system that led to knowledge about stars’ life cycles. Henrietta Swan Leavitt and others discovered thousands of stars called “variables,” whose light output changes; she was first to recognize that brighter stars had longer periods, a relation that would help to measure distances in space.

In addition to Anna Draper’s ongoing gifts, New York heiress Catherine Wolfe Bruce provided research support, money for publications, a lifetime achievement award, as well as $50,000 Pickering had requested in 1889 for a 24-inch telescope. After long delays, it finally made its way to a high peak in Peru in 1896.

Thus, during more than a century, a crew of women funded by two heiresses gathered much knowledge fundamental to astrophysics. To make this stellar library more accessible, it is currently being digitized. And unlike some who claim the women were “underpaid, undervalued victims,” Sobel’s revealing account celebrates their works and days.