Every Star Speaks for Itself

By Mary Ellen Hannibal
Dava Sobel Mia Berg

“The Glass Universe”
Dava Sobel
Viking, $30

Edward Charles Pickering had a problem. The time was 1882, and the director of the Harvard College Observatory struggled to keep it staffed with little funding. Every night the stars came out, and every night Pickering and a colleague monitored their changing brightness, making four observations per star of several hundred stars per night. So-called “variable” stars, the light output of which did just that and varied, required even more notation — one such star received 900 measures in a single night. Every morning a “computer,” a human being, manually tabulated the numbers. The stars kept shining, and Pickering couldn’t keep up with them.

As Dava Sobel explains in “The Glass Universe: How the Ladies of the Harvard Observatory Took the Measure of the Stars,” Pickering not only implored amateurs to volunteer their services, but extended his plea for help to the female sex. “Many ladies are interested in astronomy and own telescopes,” he noted, admitting that “their contributions to the science have been almost nothing.” But he argued that participating in such “a long series of observations as are detailed below” could change that. He believed women were as capable as men, if not more. And over his own long career he made good on his claim, employing an outstanding roster of women who made foundational contributions to the science of astronomy.

Since the publication of “Longitude” in 1995, Ms. Sobel has specialized in finding hidden gems in the history of science. She creates narratives that combine scientific revelation and social history, allowing her readers to ponder what science is, how it gets done, and by whom. “The Glass Universe” takes place in a particularly interesting period, when American science began to develop from an amateur pastime to a professional discipline.

The late 1800s and early decades of the 20th century could be called the Age of the Real. The Age of Discovery had brought Europeans to almost every corner of the world, and the United States itself had been recently established from sea to shining sea. A big urge to document and catalog physical things laid the groundwork for investigating deeper patterns between and among them. Natural history museums sought to comprehend the totality of what some still called the Creation by amassing specimens of plants and animals from all over the globe, to help discern a vast picture of how life forms are related. 

Pickering and his peers in astronomy worked painstakingly to document a corollary understanding of the celestial sphere, or the vast night sky. These activities continue today, largely by way of digital representation. Today we are in the Virtual Age.

Even in the late 1880s, technological advances in the tools of perception aided the documenting of the real. Ms. Sobel’s book opens with the 1882 death of Henry Draper, who developed a way to photograph the stars on glass plates. (Thus recording the “glass universe” of the title.) Pickering’s research focused on photometry, or the brightness of individual stars, which varies. Why do some stars outshine others? Before the advent of Draper plates, it was up to the observer to estimate the brightness of a star. 

Draper plates captured the spectrum of a star in detail the human eye could not see just by looking through a telescope. The glass plate photography could also best the human eye by gathering light over time. One Draper image captured 462 stars in a region where the mortal gaze had previously identified just 55. And the plates, of course, created a permanent image that could be examined and re-examined by many observers. 

As the data poured in morning after morning, Pickering assigned about half his computing staff the task of calculating star locations and orbital dynamics. A select few of “Pickering’s harem,” as his largely female staff became known, trained their attention on pattern recognition. Eventually, they helped produce a new kind of star catalog, which allowed investigation into questions about the differences in spectral appearances. 

Ms. Sobel’s book is studded with stories of remarkable women. Williamina Fleming began her association with Pickering as his household maid; he hired her at the observatory in 1881. With method and industry, Fleming made foundational contributions to what became the Draper Catalogue of Stellar Spectra, multiplying by many the definitions by which stars were classified. While her discernments did not reflect any underlying reason for different spectral appearances — maybe temperature explained them, maybe different chemical blends did — her fastidious ordering laid the groundwork for meaningful future inquiry. She paid the stars forward. 

Fleming documented more than 10,000 stars, in the process discovering 59 gaseous nebulae and more than 300 variable stars. Achieving the title of curator of astronomical photographs in 1899, she was the first woman to hold any title at Harvard University. Presenting at the National American Woman Suffrage Association in 1893, Fleming declared: “While we cannot maintain that in everything woman is man’s equal, yet in many things her patience, perseverance, and method make her his superior.”

Pickering’s “computers” had varying amounts of education. Antonia Maury (Henry Draper’s niece) was the first college graduate among the ranks, attaining a degree from Vassar College with honors in physics, astronomy, and philosophy. Scrutinizing the night sky, Maury identified a “spectroscopic binary,” or the appearance of two stars circling each other, sometimes looking like one, sometimes two. Among her substantial contributions to astronomy, she figured out a way to make a spectral classification that distinguished giant and dwarf stars. In 1897, Maury’s “Spectra of Bright Stars” became the first publication authored by a woman to be published in the Annals of the Harvard College Observatory. 

Joining the harem in 1893, Henrietta Swan Leavitt is something of a poignant case. Leavitt lost her hearing soon after graduating from Radcliffe College, and was known to be hard-working, devout, and selfless (poor thing!). Nevertheless, Leavitt found a profound pattern in the variable stars. Noting the relationship between their peak brightness and the time period over which the brightness varied, she identified the “period-luminosity relationship,” or “Leavitt’s law,” which set a measurement for distance across space. 

Closer to our contemporary world, Cecilia Payne continued the tradition of brilliant women in the observatory after Pickering’s death. Her Ph.D. in astronomy from Radcliffe was a first, her thesis brilliant. Payne’s work disrupted the commonly held belief that stars were made of the same elements as Earth, showing that helium and especially hydrogen basically composed the stars. Reviewing her dissertation, the astronomer Henry Norris Russell had her downplay this revelation; four years later he published the result and mostly got credit for it. 

Ms. Sobel’s book goes very far in counterbalancing the competitive subterfuge historically poised against women. The stories here inspire, as do their ultimate subject, the night skies.


Mary Ellen Hannibal grew up in East Hampton. Her recent book, “Citizen Scientist: Searching for Heroes and Hope in an Age of Extinction,” was named one of the best books of 2016 by The San Francisco Chronicle. 

Dava Sobel lives in Springs.

A 1918 chain of Harvard College Observatory assistants links to the telescope operator and the chief of stellar photography, at right.Harvard University Archives
A posed tableau from 1925 shows Antonia Maury, left foreground, and Cecilia Payne, at the drafting table. Harvard University Archives
Edward Charles Pickering, the director of the Harvard College Observatory, is seen standing front and center in all black, his gaze on the camera, in 1910. Also in all black, Williamina Fleming, curator of astronomical photographs, is standing at right in the front row. Special Collections Research Center, University of Chicago Library