Dava Sobel has done it again. In The Glass Universe: How the Ladies of the Harvard Observatory Took the Measure of the Stars, the author of Longitude and Galileo’s Daughter has thrown open a window into a bygone era “when computers were human” and when, at the Harvard College Observatory, most of those humans were brilliant women.
When the director of the Harvard College Observatory, Edward Pickering, used the financial gifts of Anna Draper to create the Henry Draper Memorial Project, that being a permanent photographic survey and archive of the heavens, he had no idea how important or how enormous this project would become—or of the legacy he was creating.
The Observatory had been a relatively small operation when Pickering assumed his duties as the new director in 1877, and much of his energies over the next few years went to fund-raising. In his employ he found he had a small handful of women already performing calculations in “the computing room.” Those women had deep connections to the Observatory, as they included Selina Bond, the daughter of William Cranch Bond, the first director, and Anna Winlock, a daughter of Joseph Winlock, the third director. When in 1887 Pickering hired Antonia Maury, a graduate of Vassar College who studied astronomy there under the renowned Maria Mitchell, he broke new ground. Women with an education in astronomy finally had an opening, a chance to work professionally in the field—provided they were single and remained unwed. Of course, they didn’t get paid well, and certainly earned much less than their male counterparts, but the women he hired made the most of their opportunities.
Though the Harvard computers were assigned projects that Pickering knew his highly trained male astronomers did not want to take on, and though these women were rarely allowed to do “men’s work,” i.e., actually using a telescope to make observations of the heavens, they took the primary task he assigned to them—measuring the characteristics of the spectra of stars—and revolutionized astronomy. Actually, revolutionary is not a strong enough word to capture the importance and significance of what they accomplished. These few dozen women, who often have been described as “Pickering’s harem,” created the foundation for all of modern astrophysics. The enormous importance of their contributions to our modern understanding of stars, galaxies, and the universe cannot be overstated. Furthermore, the efforts made by Pickering to create opportunities for these women during an era when none would otherwise have existed for them— opportunities they used to break through many layers of glass ceilings—merit far greater praise than that deprecating label suggests.
Pickering pioneered the idea that we must diversify our workplaces. While we may not know, beforehand, exactly what benefits will accrue to us all when we include women—or, to move this idea into the present, persons of color or different national origin or non-conforming sexual orientation—in our workforce, The Glass Universe illustrates how profound those benefits may be. The work of the Harvard College Observatory computers, done over a period of several decades and using the pioneering Harvard photographic plate collection, turned astronomy into astrophysics. The most important data plot in all of modern astronomy, known as the Hertzsprung-Russell Diagram, exists thanks to the work of Antonia Maury, Williamina Fleming, Annie Jump Cannon, and the many less-renowned women who assisted them. Astronomers still use the H-R Diagram as a tool to identify different types of stars (is it a white dwarf? a red giant? a blue straggler?). By plotting the measured brightness and temperature of every star in a star cluster on a single H-R diagram, astronomers deduce the evolutionary status of each star—is it newborn? middle-aged? dying?—and also learn the mass and radius of each star. Indeed, this data plot is the Rosetta Stone that continues to unlock the secrets of the stars.
In addition, the most important mathematical tool in all of modern astronomy, the Period-Luminosity Diagram for Cepheid variable stars—which many astronomers believe should be called the Leavitt Law to indicate how significant it is, and which is the key to measuring distances to nearly every object in the universe—exists thanks to the insight, skill, and perseverance of Henrietta Swan Leavitt. All one need do is measure the length of time required for this particular kind of variable star to cycle from brightest to faintest and back again to brightest; that number, plus Leavitt’s Law, immediately tells us how close to or how far away from the Earth and Sun this star is, whether only ten thousand light years distant or as much as fifty million light years from us.
Finally, one of the key astrophysical discoveries of the 20th century, that stars and the universe are made mostly of hydrogen, is the work of Cecilia Payne (later Payne-Gaposchkin). Pickering’s successor as director, Harlow Shapley, decided that the Harvard College Observatory should become involved in education, not just research, and to that end he wanted students to pursue a PhD in Astronomy working with Observatory astronomers. Shapley steered the limited funds he controlled for education toward Ms. Payne, who in 1925 earned the first PhD supervised by Harvard College Observatory astronomers. Since Harvard did not grant doctoral degrees to women at the time, Payne earned her degree from the school originally chartered in 1879 as the Harvard Annex, but by then known as Radcliffe College. For several years, her male seniors, including the dean of American astronomers, Henry Norris Russell himself, dismissed her conclusions as to the overwhelming abundance of hydrogen in stars as “almost certainly not real.” Finally, however, in 1929, Russell decided that Payne was correct, and with his imprimatur the nearly all-male community of astronomers around the world embraced her conclusions.
Russell is deservedly famous. The H-R Diagram is named for him; the most prestigious award in American astronomy is the Henry Norris Russell Lectureship given annually by the American Astronomical Society on the basis of a lifetime of eminence in astronomical research. Payne is a footnote to astronomical history. The names of Maury, Fleming, Cannon, and Leavitt sometimes appear in textbooks, but they and their contributions to our knowledge of the universe should be widely known, not just to graduate students in astronomy. In addition, the contributions of Anna Draper and Catherine Wolfe Bruce—whose financial gifts enabled Pickering to create the Draper Project and hire the Harvard computers to study the light from the millions of stars on these tens of thousands of photograph plates, which in turn triggered an explosion in our knowledge about the universe—should be more fully acknowledged. Perhaps Sobel’s book will right some of these wrongs.