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An Astronomer of Note

Williamina Paton Stevens was born on May 15, 1857, in Dundee, Scotland. Her father was Robert Stevens who was a carver and gilder, her mother was Mary Walker. In 1877 she married James Orr Fleming who was a widower and an accountant. She worked for a while as a teacher but the couple soon emigrated to Boston, Massachusetts. She was 21 years old. The couple had one son, Edward.

She was abandoned by her husband and had to find a way to support herself and her young son. She worked as a domestic in the home of Professor Edward Charles Pickering, who was the Director of the Harvard College Observatory (HCO).

Pickering’s wife, Elizabeth recognized real promise and talent in Williamina that went way beyond domestic work. At the urging of his wife, Pickering hired Williamina to conduct part time administrative work in his observatory. He was often frustrated by the inaccuracy of his current staff and was heard to say in a fit of pique, “Why, my Scottish maid could do better!” She did. In 1881, he formally invited her to join the HCO staff and taught her to analyze stellar spectra. Williamina became a founding member of the Harvard Computers. They were all women and were like human computers that Pickering hired to compute mathematical classifications and edit the observatory’s publications. Who says women can’t do math?

Mary Anna Draper, the wealthy widow of astronomer Henry Draper began the Henry Draper Memorial in order to fund the HCO’s research. HCO then undertook the task of establishing the Henry Draper Catalog. This was an auspicious endeavor and a long term project with the goal being to obtain the optical spectra of as many stars as possible and to index and clarify those stars by spectra.

Fleming was placed in charge of this project. She advocated a very straightforward approach to this work. A former colleague had begun the work using a much more complicated approach. Williamina felt that the simpler the classifications were, the better.

Current images that the HCO had contained photographed spectra of stars that extended into the ultraviolet range which actually allowed a much more accurate classification and recording by hand and through an instrument at night. Fleming devised a system for classifying the stars according to the relative amount of hydrogen observed in their spectra, known as the Pickering-Fleming classification. Note, Pickering is listed first in this discovery. Stars showing hydrogen as the most abundant element were classified A; those of hydrogen as the second most noticeable element were classified B; and so on, using this pattern.

Later, her colleague, Annie Jump Cannon, reordered this classification system basing her process on surface temperature of stars. This system resulted in the Harvard system for classifying stars that is still in use today.

HCO published the first Henry Draper Catalog in 1890 after years of work ty the female computer team. It contained more than 10,000 stars classified according to their spectrum. Most of these were done by Fleming who also made it possible to go back and compare recorded plates by organized thousands of photographs by telescope along with other identifying factors. She was appointed Curator of Astronomical Photographs at Harvard in 1898. She was the first woman to hold that position.

During her career, Fleming discovered a total of 59 gaseous nebulae, over 310 variable stars, and 10 novae. In 1888 she discovered Horsehead Nebula on a telescope-photogrammetry place made by the astronomer W. H. Pickering, brother of her boss, E.C. Pickering. However, professional publications neglected to give her credit for the discovery, committed her name from the Catalogue index and simply attributed the entire work to “Pickering.” B By the time the second Dreyer Index Catalogue was published in 1908, Fleming and her female colleagues at the HCO were sufficiently well-known and received proper credit for their discoveries.

The Women of the Harvard Computers were famous during their lifetimes, but were pretty much forgotten in the century that followed. In 2015 about 118 boxes with each containing 20 to 30 notebooks compiled by the women computers and early astronomers at Harvard. They were preserved and on display at the Harvard-Smithsonian Center for Astrophysic’s Wolbach Library, along with dozens of volumes of Flemings works. The collection is being digitalized by volunteers.

Fleming was a member of the Astronomical and Astrophysical Society of America and the Astronomical Society of France. She was an honorary member of the Royal Astronomical Society of London and in 1906 the first American woman to be elected. She was awarded the Guadalupe Almendaro Medal by the Astronomical Society of Mexico for her discovery of new stars. She was appointed an honorary fellow in astronomy at Wellesley College and the Fleming lunar crater was jointly named after her and Alexander Fleming (not related).


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