Astronomy was not exactly a progressive force in support of the equality of women in the 19th century.  The Royal Astronomical Society in London was founded in 1820 and restricted its formal membership to men until 1915.  But even such an archaic policy was sometimes bent just a little to admit high-achieving female astronomers from time to time.  So, the first two such women, Caroline Herschel and Mary Somerville, were made honorary members of the Society in 1835.

Mary Somerville was a polymath, and astronomy was but one of the fields to which she made important contributions.

Not So Humble Beginnings

Unlike Herschel, who came from a humble background in Germany, Mary was born into the distinguished Fairfax family from the Scottish Borders.  She was encouraged in her education (albeit not with the enthusiastic support well-bred boys typically received) and demonstrated a keen thirst for knowledge from an early age.  Under tutors, she studied Latin, mathematics, astronomy, geography, and art.

“I never lost sight of the main object of my life, which was to prosecute my studies.” – Mary Somerville

Following a rather typical path for a young woman of her station in life, Mary attended gala social events, concerts, and the theater, but her dedication to scientific inquiry never abated.  Eventually, she married (reluctantly, some accounts say) the affluent but overbearing Samuel Greig when she was 24 years old.  Greig was not, it seems, a particularly enlightened gentleman when it came to his wife’s continuing intellectual development.  Perhaps fortunately for Mary, as it turned out, he died after only three years of marriage, in 1807.

‘The Queen of 19th Century Science’

With Captain Greig’s death came the means and freedom to pursue her true interests – a pursuit Mary took up with gusto.  Encouraged by Professor John Playfair (yes, that was his name) of the University of Edinburgh and by her far more supportive second husband, Dr. William Somerville, she immersed herself in the physical sciences, including astronomy.  Mary published papers and several books, and translated Pierre-Simon Laplace’s Mécanique Céleste (under the title The Mechanism of the Heavens).  “I translated Laplace’s work from algebra into common language,” she said.

Her gift for translating the complex ideas of science and mathematics into clear language that could be readily understood by intelligent readers may have been Somerville’s greatest contribution to 19th century scientific advancement.  Her Physical Geography, published in 1848, was the first geography textbook written in English and was in common use into the early 20th century.

Divining an Unseen Planet

Among Somerville’s more notable contributions to astronomical inquiries of the mid-19th century was her informed conjecture (in her book On the Connection of the Physical Sciences) concerning a then-hypothetical planet “perturbing” Uranus, which had been identified, in 1781, by William Herschel.

Those [the tables] of Uranus, however, are already defective, probably because the discovery of that planet in 1781 is too recent to admit of much precision in the determination of its motions, or that possibly it may be subject to disturbances from some unseen planet revolving about the sun beyond the present boundaries of our system. If, after a lapse of years, the tables formed from a combination of numerous observations should be still inadequate to represent the motions of Uranus, the discrepancies may reveal the existence, nay, even the mass and orbit, of a body placed for ever beyond the sphere of vision. – Mary Somerville (from The Connection of the Physical Sciences, 6th edition, 1842)

Somerville was not alone in her speculation about an “unseen planet” to account for the perturbations in the orbit of Uranus, but, in 1842, she was among the first to publish her views on the possibility.  Four years later, John Couch Adams and Urbaine Le Verrier separately presented calculations that led Johann Gottfried Galle to make the formal discovery of Neptune.

Neptune as viewed from Voyager 2 (Image credit: NASA/JPL)

Moving to the Continent

When William Somerville became ill, in 1838, Mary and he moved to Italy.  Her husband recovered well enough to live another 20 years, and Mary devoted herself to family, her studies, and her writing.  She spent most of the rest of her life in Italy and died in Naples, in 1872.

Before her passing, Somerville received numerous honors and was elected to a bevy of scientific societies in Europe and America.  At Oxford University, Somerville College is named after her, as are an island in the Barrow Strait, a crater on the moon, and an asteroid.  In February 2016, Somerville was chosen to appear on the new Scottish £10 banknote.

Somerville Crater on the Moon from Apollo 15. (Credit: NASA)