A Maid Turned Astronomer
In 1881, Harvard Observatory director Edward Charles Pickering faced a challenge. Advances in astrophotography had created an avalanche of star data that his staff could not process fast enough.
Frustrated with his male assistant’s inefficiency, Pickering dismissed him and gave the job to his maid, Williamina Fleming. Her meticulous work proved so valuable that she stayed at Harvard for 34 years, eventually overseeing a staff of women who became known as “Pickering’s Harem.”
The Work of the Computers
Between 1877 and 1919, more than 80 women worked at the observatory, examining photographs of the night sky. They reduced images for clarity, cataloged stars, and recorded magnitudes and positions. The tasks were repetitive, but they built the statistical backbone for astronomical theory.
The women earned between 25 and 50 cents per hour, about half the wage of men performing similar duties. Fleming rose to Curator of Astronomical Photos after two decades of service, but advancement beyond supervisory roles was rare.
Science Behind the Data
The success of the Harvard women relied on improvements in photographic technology. Richard Maddox’s dry plate method in 1871 allowed images to be prepared in advance, while Charles Bennett’s 1878 discovery of heat sensitivity enhanced their exposure to starlight.
Pickering expanded astrophotography at Harvard in the 1880s, producing thousands of plates that required classification. Women, viewed as inexpensive and suited for clerical work, were hired to interpret the images. Though limited in scope, their contributions laid the groundwork for major discoveries.
Annie Jump Cannon’s Breakthrough
Among Pickering’s computers, Annie Jump Cannon emerged as a pivotal figure. Born in Delaware in 1863, she studied at Wellesley College under Sarah Frances Whiting before joining Harvard in 1896. Building on earlier work by Antonia Maury and Williamina Fleming, Cannon created a simplified system of stellar classification.
In 1922, the International Astronomical Union adopted her scheme—still in use today—as the official system for categorizing stars. In 1938, she became Harvard’s William C. Bond Astronomer, two years before her retirement and three years before her death.
Lasting Impact of the Harvard Observatory
Edward Pickering directed the Harvard Observatory from 1877 until 1919. During his tenure, he received honors such as the Bruce Medal, and lunar and Martian craters now bear his name. While he opened doors for women in astronomy, their work was often credited to the institution rather than to individuals.
Cannon’s system endures as the “Harvard classification,” a reminder of the era when women at the observatory, working quietly for long hours at low pay, transformed the way humanity understands the stars.
In 1881 at Harvard Observatory, Edward Charles Pickering dismissed a male assistant and hired his maid, Williamina Fleming, to handle a surge of astrophotography data.
Fleming excelled, stayed 34 years, and supervised a growing team that processed the night sky…🧵👇 pic.twitter.com/Z08SQh8Gq0
— Fascinating True Stories (@FascinatingTrue) September 18, 2025