The Harvard Computers, a name that whispers of meticulous calculation and quiet dedication, were a collective of women laboring as highly skilled workers, meticulously processing the torrent of astronomical data that flowed into the Harvard College Observatory in Cambridge, Massachusetts. This intellectual engine, humming with precision from 1877 to 1919 under the directorship of Edward Charles Pickering and subsequently guided by the formidable Annie Jump Cannon after his passing, was far more than a mere clerical pool. These women weren't just crunching numbers; they were deciphering the very language of the cosmos, weaving patterns from the raw observations that male astronomers, ensconced in their evening vigils, couldn't possibly manage alone.
Their challenge was immense: to impose order on the celestial chaos, to devise a system that could categorize the stars based on the subtle nuances of their light. It was a task that demanded not just accuracy, but profound insight. Annie Jump Cannon, a name that resonates even now, achieved a level of fame during her lifetime that few could attain. Her meticulously crafted stellar classification system, born from countless hours of poring over spectral data, remains the bedrock of modern astronomical understanding. Then there was Antonia Maury, who, with a keen eye for detail, discerned in the stellar spectra a method for gauging the relative sizes of stars, a crucial step in understanding their physical properties. And Henrietta Leavitt, whose groundbreaking work revealed how the rhythmic pulses of certain variable stars could act as cosmic yardsticks, measuring the vast distances that separate us from the furthest reaches of the universe.
The roster of these remarkable women, often overshadowed by their male contemporaries, included figures like Mary Anna Draper, whose patronage was instrumental; Williamina Fleming, a tireless classifier; Anna Winlock, who meticulously reduced observational data; and Florence Cushman, whose organizational prowess kept the vast datasets manageable. Though they began their careers primarily as "computers" – a term that at the time referred to human calculators – their contributions transcended mere computation. They became astronomers in their own right, publishing their findings in significant research articles, shaping the trajectory of astronomical discovery.
History
The latter half of the 19th century presented the Harvard College Observatory with a peculiar kind of crisis: an overwhelming abundance of data. Advances in photographic technology, while revolutionary, had unleashed a deluge of stellar images, captured on an ever-growing collection of plate negatives. It was a problem of plenty, and Edward Charles Pickering, the observatory’s director, found a pragmatic, albeit controversial, solution in hiring women. He brought on board a team of over eighty women, whom he dubbed "computers."
Pickering, it's said, didn't consider observational astronomy the most fitting pursuit for women. Yet, his decision to hire them over men was influenced by a confluence of factors, not least of which was the economic reality of the time. Men commanded significantly higher salaries, meaning Pickering could employ a larger workforce for the same budget. This was a critical advantage when the sheer volume of astronomical data threatened to overwhelm the observatory's capacity. Even those women who held degrees in astronomy found themselves earning wages comparable to unskilled workers – a paltry 25 to 50 cents per hour. While this was more than a factory operative might earn, it was less than a clerical worker. Many relied on financial support from family and friends, and some shared living spaces to mitigate the financial strain. Despite the meager compensation, Pickering’s initiative was, in its own way, a form of advocacy for women in a field that was notoriously difficult for them to penetrate. He saw their work as a public demonstration of women's intellectual capabilities, worthy of higher education.
The very first woman to join this pioneering group was Anna Winlock. Six years later, in 1881, Williamina Fleming was hired, and together, Fleming and Pickering continued to expand the team throughout the early twentieth century. Some women, eager to gain a foothold in astronomy, even offered their services without pay, a testament to their passion and the exclusivity of the field.
The role of a "computer" at the observatory was, by its nature, a position of lower standing, marked by low pay and limited prospects for advancement. Within the framework of the Henry Draper Memorial project, these women were primarily tasked with the meticulous measurement of stellar brightness, position, and color. Their objective was to photograph stars and then classify their spectral characteristics. This division of labor was stark: male astronomers would capture the photographic plates during the night, and then, during the day, the women would analyze this data. Their tasks included classifying stars by calculating their precise positions and movements, predicting the orbits of comets, and reducing the photographic plates. This reduction involved accounting for atmospheric distortions, parallax, and instrumental errors to produce the clearest possible representations of celestial objects. While the work could be repetitive, it demanded unwavering attention to detail and absolute accuracy. Williamina Fleming herself described it as "so nearly alike that there will be little to describe outside ordinary routine work of measurement, examination of photographs, and of work involved in the reduction of these observations." The advent of photographic plate technology was indispensable. The use of dry, color-sensitive plates allowed for longer exposure times, significantly increasing the accuracy of the photographs and extending the range of observable stars. This technological leap enabled the women to classify stars with a precision previously unimaginable.
The observatory, empowered by the diligent efforts of the Harvard Computers, achieved several monumental breakthroughs in classifying and cataloging stars. Foremost among these was the monumental Henry Draper Catalogue. Following the death of Henry Draper in 1882, his widow, Mary Anna Palmer Draper, provided crucial funding for this ambitious undertaking, initially at the Mount Wilson Observatory before the project was firmly established at Harvard. Williamina Fleming spearheaded the initial classifications, publishing her findings in 1890. Subsequently, Antonia Maury, working alongside Pickering, refined the system and conducted further research on stellar spectra, publishing her own contribution in 1901. In 1908, Henrietta Leavitt made a discovery that would echo through the halls of astronomy: she identified a direct relationship between the pulsation period of a Cepheid variable and its intrinsic brightness. This revelation provided astronomers with a vital tool for measuring cosmic distances. Between 1912 and 1915, Annie Jump Cannon and her team achieved an astonishing rate of classification, averaging 5,000 stars per month. Florence Cushman played a critical role in organizing and processing this immense volume of data. The Henry Draper Catalogue itself was published in stages between 1918 and 1924. After Pickering's death in 1919, Cannon assumed leadership of these ongoing projects. An expanded version of the catalogue, classifying over 46,850 stars, was published between 1925 and 1936, a testament to the enduring legacy of the Harvard Computers.
As the initial phases of the catalogue concluded, several women continued to make significant contributions. Margaret Walton Mayall advanced the field of stellar spectra classification and later led the American Association of Variable Star Observers. Helen Sawyer Hogg specialized in cataloging variable stars within globular clusters, laying crucial groundwork for understanding stellar evolution and the architecture of the universe. And Cecilia Payne-Gaposchkin, through her groundbreaking work, definitively proved that stars are predominantly composed of hydrogen and helium. Muriel Mussells Seyfert expanded our knowledge of nebulae by discovering three new ring nebulae on photographic plates, adding to the catalogue of known planetary nebulae.
Notable members
Mary Anna Palmer Draper
Mary Anna Palmer Draper (1839–1914) was an American patron of science whose influence extended to the founding of the Mount Wilson Observatory. As the widow of Dr. Henry Draper, an astronomer whose ambitious project to classify stars by their chemical composition was cut short by his death, Mary Draper felt a profound responsibility to see his work completed. Recognizing the monumental scale of the task, she sought assistance from Pickering, a close friend of both herself and her late husband. Pickering offered to help finalize her husband's research and encouraged her to publish his findings up to that point. Draper agreed to entrust Pickering with her husband's plates, personally transporting them to Harvard, a testament to her dedication. While at the observatory, she observed the ongoing projects and met the women who would become known as the Harvard Computers. After careful deliberation in 1886, she decided to endow the Harvard Observatory with both financial resources and her husband's telescope, specifically for the purpose of photographing stellar spectra. This decision marked a pivotal moment, ensuring her husband's legacy would endure through continued astronomical research. She funded this endeavor with her own inheritance, driven by a deep commitment to her husband's scientific vision. A devoted supporter of the observatory and a close confidante of Pickering, she also funded an expedition in 1900 to observe a total solar eclipse.
Williamina Fleming
Williamina Fleming (1857–1911), a Scottish immigrant, rose to become a pivotal figure in the photographic classification of stellar spectra. Fleming's connection to Harvard began not as an astronomer, but as Pickering's housemaid. Her aptitude and diligence quickly became apparent, leading to her assignment to improve an existing stellar spectra catalog. This task evolved into her leadership of the Henry Draper Catalogue project. Fleming developed a classification system for stars based on their hydrogen content and played a significant role in identifying the peculiar nature of white dwarf stars. Her career advanced further when, in 1899, she was appointed Harvard's Curator of Astronomical Photographs, a position of considerable distinction. She remained the sole female curator until the 1950s. Her accomplishments earned her recognition as the first female American citizen to be elected to the Royal Astronomical Society in 1907. Throughout her career, Fleming classified an impressive 10,000 spectra and discovered over 50 nebulae and more than 300 stars. She passed away from pneumonia at the age of 54, still actively engaged in her work at the observatory.
Antonia Maury
Antonia Maury (1866–1952), an American astronomer, made significant contributions to the understanding of spectroscopic binaries. As the niece of Henry Draper, and with a recommendation from Mrs. Draper, she was hired as a computer at the age of 22. A graduate of Vassar College with honors in physics, astronomy, and philosophy, Maury's academic achievements presented a quandary for Pickering, who was reluctant to offer her the standard computer salary. Nevertheless, he hired her. Initially, Maury was tasked with measuring the spectra of the brightest stars. Later, Pickering assigned her the complex task of reclassifying stars following the publication of the Henry Draper Catalog. In 1889, her examination of images of Mizar led to the groundbreaking discovery that it was, in fact, a binary star system, identified by the appearance of two distinct K-lines at intervals. Maury went on to develop and refine a stellar classification system, which was eventually adopted by the International Astronomical Union. She left the observatory in 1891 to teach at the Gilman School in Cambridge, Massachusetts but returned in 1893 and 1895 to publish her extensive observations of stellar spectra, a monumental work completed with the assistance of Pickering and the computing staff, and published in 1897. Maury rejoined Harvard College Observatory in 1918 as an adjunct professor. Under the directorship of Harlow Shapley, her work began to be published under her own name, and she remained at the observatory until her retirement in 1948.
Anna Winlock
Anna Winlock (1857–1904), an American astronomer, played a crucial role in cataloging stars for the Henry Draper Catalogue. Some of the earliest women hired as computers had familial ties to the male staff at Harvard. Winlock, one of the first Harvard Computers, was the daughter of Joseph Winlock, the observatory's third director and Pickering's immediate predecessor. Anna joined the observatory in 1875, seeking to support her family after her father's untimely death. She took on the challenging task of reducing her father's unfinished meridian circle observations, salvaging a decade's worth of data that had been rendered unusable. Winlock also contributed to the "Cambridge Zone" project, a significant section of stellar cataloging. Over more than twenty years, her team's work on the Cambridge Zone was instrumental in the creation of the Astronomische Gesellschaft Katalog, a comprehensive catalog used by observatories worldwide. Within a year of Winlock's hiring, three other women joined the staff: Selina Bond, Rhoda Sauders, and another whose identity is uncertain but likely connected to an assistant astronomer. In 1886, Anna's younger sister, Louisa Winlock, also joined her in the computing room.
Annie Jump Cannon
Annie Jump Cannon (1863–1941), an American astronomer of immense stature, created a comprehensive catalog of stars, classifying and meticulously recording their properties. Following Pickering's death in 1901, she assumed a leadership role at the observatory. Cannon, a graduate of Wellesley College, was hired by Pickering to classify the stars of the Southern Hemisphere. During her time at Wellesley, she had studied astronomy under Sarah Frances Whiting, one of Pickering's former students. Cannon became the first female assistant to conduct night studies of variable stars, analyzing their light curves to understand the variations in their brightness and infer their causes.
Building upon the foundational work of Antonia Maury and Williamina Fleming, Cannon significantly refined the existing star classification system, which was based on temperature. In 1922, the International Astronomical Union officially adopted Cannon's system, which remains the basis for today's familiar O B A F G K M stellar classification. During Pickering's 42-year tenure, which concluded shortly before his death in 1919, he received numerous accolades, including the prestigious Bruce Medal. Craters on the moon and Mars bear his name. Cannon's enduring achievement, however, was recognized as the Harvard—not the Cannon—system. She also meticulously organized and tabulated variable stars, making them easier to identify and compare. Rebecca Dinerstein Knight notes Cannon's extraordinary efficiency: she could classify the spectra of 300 stars per hour, leading to a lifetime tally of over 350,000 classified stars.
Cannon was a trailblazer in receiving recognition for her scientific work. She was the first woman to be awarded an honorary doctorate from the University of Oxford, the Henry Draper Medal from the National Academy of Sciences, and the first woman to hold an officer position in the American Astronomical Society. In 1934, she established the Annie Jump Cannon Award to support women in postdoctoral research. The first recipient of this award was Cecilia Payne-Gaposchkin, recognized for her crucial contributions to the analysis of stars and their spectra. The award ceremony, held at an American Astronomical Society meeting, included a $50 prize and a gold pin for Gaposchkin.
Henrietta Leavitt
Henrietta Swan Leavitt (1868–1921), an American astronomer, revolutionized our understanding of cosmic distances through her study of variable stars. Leavitt joined the observatory in 1893, bringing with her a strong academic background in mathematics and experience gained from travel and teaching. Her work at Harvard initially focused on measuring stellar brightness through photometry. She discovered hundreds of new variable stars, expanding her research to encompass variables across the entire sky in collaboration with Annie Jump Cannon and Evelyn Leland.
Leavitt's most profound discovery emerged from her study of Cepheid variables in the Small Magellanic Cloud. By comparing stars at roughly the same distance from Earth, she established a critical relationship: the period of a Cepheid's pulsation was directly correlated with its apparent brightness. This implied that their absolute brightness was also dependent on their period, transforming Cepheid variables into powerful standard candles for measuring vast cosmic distances. This insight was fundamental to the modern understanding of the universe's immense scale and continues to be a cornerstone of the cosmic distance ladder.
Tragically, Pickering published Leavitt's groundbreaking work with his own name as a co-author, a common practice of the era that further obscured her individual brilliance. Nevertheless, her legacy provided the foundation for future generations of astronomers. Edwin Hubble, for instance, utilized Leavitt's method to calculate the distance to the Andromeda Galaxy, a discovery that revealed the existence of countless other galaxies beyond our own.
Florence Cushman
Florence Cushman (1860–1940), an American astronomer at the Harvard College Observatory, made significant contributions to the Henry Draper Catalogue. Born in Boston, Massachusetts in 1860, she completed her early education at Charlestown High School in 1877. Cushman began her employment at Harvard in 1888 under Edward Pickering. Her meticulous classifications of stellar spectra were incorporated into the Henry Draper Catalogue between 1918 and 1934. She remained at the observatory until 1937, passing away in 1940 at the age of 80.
Throughout her nearly fifty-year career at Harvard, Cushman employed the objective prism method to analyze, classify, and catalog the optical spectra of hundreds of thousands of stars. The photographic revolution of the 19th century had enabled unprecedented detail in astronomical observation. While male astronomers captured the images on glass plates at night, women like Florence were responsible for the daytime analysis, reducing spectral data, computing magnitudes, and meticulously cataloging their findings. She is credited with determining the positions and magnitudes of the stars featured in the 1918 edition of the Henry Draper Catalogue, which documented the spectra of approximately 222,000 stars.