On the evening of 1 October 1847 there was a party downstairs in the Mitchell house on Vestal Street, Nantucket. Maria Mitchell, twenty eight years old and the island’s librarian, left the guests, climbed to the roof of the Pacific Bank where her father worked, and pointed a two inch Dollond telescope at the sky above Polaris.
She found a faint smudge that was not on any of her charts. She noted the position, went back down, and told her father that she thought she had a comet.
Why a Librarian Owned the Sky
Nantucket was a whaling town, and whaling depended on navigation. Maria’s father, William Mitchell, rated chronometers for the whaling fleet, which meant timing star transits precisely enough to tell a captain whether his clock could be trusted for three years in the Pacific. The family had instruments on the roof because the instruments were the business.
Maria did the observing with him from childhood. By twelve she was counting seconds for him during an annular eclipse. By seventeen she was running her own school, and she famously admitted the island’s Black children at a time when the public school would not. By twenty she had the librarian’s post at the Nantucket Atheneum, which gave her a salary, a building full of books and long quiet days in which to read mathematics.
This is worth stating plainly, because the usual telling makes her a lucky amateur. She was not. She had been sweeping the same sky night after night for years, deliberately, looking for exactly this, using the standard method of the time: memorise the field, compare it with the charts, and watch for anything that moves.
The Medal, and the Race to Claim It
In 1831 Frederick VI of Denmark had established a gold medal for the discovery of a telescopic comet, one invisible to the naked eye. The conditions were strict. The discovery had to be reported to the observatory at Altona by the first available post, and the first to report won.
William Mitchell wrote immediately to William Cranch Bond at Harvard, who was the natural conduit to Europe. Then the trouble started. The letter travelled by boat and post from an island in Massachusetts to Cambridge, and from Cambridge across the Atlantic.
Meanwhile, on 3 October, Francesco de Vico spotted the same comet in Rome and reported it at once to Altona. Wilhelm Rümker at Hamburg saw it on 7 October. De Vico’s report arrived first, and by the ordinary reading of the rules the medal was his.
What followed was a small diplomatic campaign. Bond and Edward Everett, the president of Harvard and a former United States minister to Britain, argued the case through official channels: the priority of observation was Mitchell’s by two days, documented and timed, and the delay was in the mail rather than in the astronomy. It took until 1848. Christian VIII, by then on the Danish throne, awarded the medal to Maria Mitchell.
The object is catalogued as C/1847 T1 and was known for the rest of the century as Miss Mitchell’s Comet.
What the Medal Actually Changed
Almost immediately, in 1848, she was elected to the American Academy of Arts and Sciences, the first woman to be admitted. The certificate is a small monument to institutional discomfort: the word “Fellow” was struck out by hand and “Honorary Member” written in, because nobody could work out what to call her.
In 1849 the United States Nautical Almanac hired her to compute the tables of Venus. This was salaried mathematical work, done from Nantucket, for the navy. She held the post for nineteen years. The job title was “computer”, and it meant precisely that: a person who performed astronomical calculation for a living, in the same tradition that would later produce the human computers who calculated the Apollo trajectories.
In 1865 Vassar College made her its first professor of astronomy and gave her a twelve inch refractor, the third largest telescope in the country. She taught by taking students out at night and letting them handle the instrument, on the principle that astronomy is not a subject you can learn from a book about astronomy.
Then she discovered that several younger male professors were paid more than she was. She asked for the difference. She got it.
The Comparison That Makes the Point
Half a century earlier, Caroline Herschel had found eight comets and become the first woman paid a salary for scientific work, fifty pounds a year from George III, as assistant to her brother. The phrasing of the appointment matters: assistant. Her own discoveries were made in the gaps of somebody else’s programme.
Mitchell’s position was different in one specific way. The comet was hers, found on her own sweep, and the award named her. That is why the episode was useful to other women in a way that talent alone never is. It produced a document with her name on it, issued by a king, which is the kind of thing committees find difficult to argue with.
She knew it, too, and spent the rest of her life using it. She co founded the Association for the Advancement of Women and chaired its science committee. She was blunt about what she thought the obstacle was, and it was not aptitude. “The eye that directs a needle in the delicate meshes of embroidery will equally well bisect a star with the fine lines of a transit instrument.”
What She Did Not Get
Her observations of Jupiter’s and Saturn’s satellites, her work on sunspots photographed daily at Vassar, and her nineteen years of Venus tables never produced the kind of result that gets a law or an effect named after a person. She is remembered for one October evening and for being first through several doors.
That is a fair description of most working astronomers of the nineteenth century, male or female. The difference is that the men were allowed to be ordinary professionals, and she had to be exceptional in order to be permitted to be ordinary. Mary Somerville, whose reputation rested on explaining other people’s mathematics beautifully, ran into the same arithmetic on the other side of the Atlantic.
Mitchell resigned from Vassar in 1888 and died the following year. The crater Mitchell on the Moon is named after her. So is the observatory on Nantucket, which still stands on Vestal Street, a short walk from the roof where she went up in the middle of a party to check something she had noticed.
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