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Williamina Fleming - Astronomy Pioneer

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Before the days of suffragettes, at a time when the concept of equality of the sexes could not even have been imagined, one woman, Scottish astronomer Williamina Paton Fleming née Stevens (1857 - 1911), struggled for recognition in a male-dominated profession.

Scottish Maid

Williamina Paton Stevens was born in Dundee, Scotland, on 15 May, 1857, to Robert and Mary Stevens. She was educated at public schools, where she excelled in her studies enough to leave at the age of 14 and take employment as a teacher. Some six years later, on 26 May, 1877, Williamina married James Orr Fleming and the newlyweds emigrated to Boston, Massachusetts, USA. While she was expecting their first child her husband abandoned her, so she had to find work to support herself and son Edward after his birth. In those Victorian days of old, a single mother might well have starved or ended up working as a prostitute. There was no such thing as social security; if a person didn't have an income then they ended up in the poorhouse.

Williamina Fleming was offered employment as a housekeeper to Professor Edward Charles Pickering (1846 - 1919), the Director of Harvard College Observatory, but she made a better assistant than some of his students, so he ended up giving her a job examining photographic plates. Her role as his assistant was formalised in 1881, and she set about classifying stars according to their spectra. The new classification system eventually became known as the Pickering-Fleming System.

After the death of Dr Henry Draper (1837 - 1882), a prominent scientist and amateur astronomer of the day, his widow approached the Observatory and funded a commission to catalogue all of the stars which her late husband had recorded. It was a phenomenal task and Pickering engaged women workers called 'computers' to compute all the data from the thousands of photographic plates. The women were doing by hand the work that computers do today. The first person in charge of the workers left within weeks, so Williamina Fleming took over the role.

Over the course of the next few years, Williamina Fleming and 'Pickering's harem' as the scientific community dubbed them, catalogued over 200,000 stars, the data being eventually published in the 1890 multi-volume Draper Catalogue of Stellar Spectra. We now use that data as the HD system of stellar classification. Rather than co-authorship, Williamina Fleming received a credit in the foreword for her contribution. All of the edicts published by the Observatory during Williamina's tenure as Pickering's assistant were edited by her. By 1900 she was earning enough as a photographic analyser to support her son's higher education at the Massachusetts Institute of Technology.

Pickering Discoveries

Professor Pickering claimed 15 planetary nebulae (14 of which were awarded NGC numbers, the other could not be verified), between 1880 and 1883. Over a decade later, open cluster IC 2581 and emission nebula IC 2599, both members of Carina, were added to his list of discoveries under the date 10 May, 1893.

John Dreyer

John Louis Emil Dreyer was Director of the Armagh Observatory from 1882 to 1916. He was compiling the New General Catalogue, bringing together the major discoveries of William Herschel and other long-gone astronomers. Newer findings were included in his Index Catalogue (the IC). IC 1297, a planetary nebula in Corona Australis, was found by Williamina Fleming on a photographic plate in 1894. Dreyer attributed the discovery of IC 1297 to Pickering, registering it as PK 358-21. The other Williamina Fleming discoveries Dreyer awarded to Pickering were:

  • IC 418, a planetary nebula (The Spirograph Nebula) in Lepus. This remains catalogued as PK 215-24
  • IC 420, an emission nebula in Orion, since reclassified by the NGC/IC project as 'Diffuse Nebula or Supernova Remnant'
  • IC 421, a spiral galaxy in Orion.
  • IC 423, IC 426, IC 427 and IC 428, all bright emission nebulae in Orion
  • IC 424, IC 430, IC 431, IC 432 and IC 435, all reflection nebulae in Orion
  • IC 1266, a planetary nebula in Ara. This remains catalogued as PK 345-8

By the time of the issue of the second edition of the Index Catalogue, Williamina Fleming's other discoveries had been acknowledged by the scientific community so she was becoming too well-known to be ignored, and she got credited.

Williamina Fleming Discoveries and Honours

In 1899 the title of Curator of Astronomical Photographs was awarded to Williamina Fleming, the first time such a position had been given to a woman. She was made a member of the Royal Astronomical Society of London on 11 May, 1906.

In 1907 her book A Photographic Study of Variable Stars was published, containing data on 222 variable stars. By then Williamina Fleming had discovered over 50 nebulae, including 'Pickering's Triangle' (eventually named after her boss!), the enigmatic Horsehead Nebula, ten novae, many Wolf-Rayet1 stars and over 300 variable stars. RS Ophiuchi is a recurrent nova: a white dwarf and red giant binary star system which interact. The RS Ophiuchi nova of 1898 was noted by Williamina Fleming after she identified it on a photographic plate. The Guadalupe Almendaro medal was awarded to her by the Mexican Astronomical Society for her discovery of new stars.

Williamina Fleming also wrote in her journals about very hot, dense stars at the end of their stellar lifetime, calling them 'white dwarfs'. Astronomers now know that our Sun will become a white dwarf when it runs out of hydrogen. Those scientific papers were published in 1910, just prior to Williamina's death from pneumonia on 21 May, 1911, aged 54 years. The book Stars Having Peculiar Spectra was published posthumously in 1912. Williamina Fleming's success in a male-dominated profession, lauded (eventually) by her peers, adequately displays her triumph in the face of prejudice.

Notable Discoveries

CatalogueOther Catalogue NumberTypeConstellationDistance
(light years)
IC 434 inc
Barnard 33
 Red emission
and dark nebulae
Orion1,600The Horsehead Nebula (1888)
IC 418PK 215-24Planetary nebulaLepus2,000The Spirograph Nebula (1891)
IC 2553PK 285-5Planetary nebulaCarina13,400Discovered in 1893
IC 1297PK 358-21Planetary nebulaCorona Australis7,800Discovered in 1894
IC 2448Fleming 80Planetary nebulaCarina10,100Discovered in 1898
IC 2501Fleming 101Planetary nebulaCarina5,642Discovered in 1904
Simeis 3-188 Supernova remnantCygnus1,470Pickering's Triangle

1Wolf-Rayet stars are named after their discoverers Charles Wolf and Georges Rayet. They are blue supergiants, over 20 times the mass of our Sun, which eject stellar wind at a phenomenal speed. They have a high rate of mass loss, equivalent to an Earth mass per year. This shortens the life of the stars and will eventually cause them to go supernova.

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