With comets very much in the news these past few days, following the spectacular success of the Rosetta mission, I’m been thinking some more about Caroline Herschel (1750-1848), the first professional female astronomer, and the subject of my 2011 novel, Variable Stars. Between 1786 and 1797, Herschel discovered eight comets - one of which (35P/Herschel-Rigollet) bears her name. There is also an asteroid (281 Lucretia) named after her, as well as a crater on the Moon (C. Herschel). During her long life - she lived to be 97 - she was also responsible for cataloguing over 2,500 nebulae, an achievement for which she was awarded not one, but two, gold medals. She fraternised with the most eminent astronomers of the age, and was described by one of them, the German astronomer Karl Felix Seyffer, as the ‘most noble and worthy priestess of the new heavens’. She was, in a word, something of a superstar.
With so starry a C.V., it may seem surprising that Caroline Herschel is not better known, but in spite of her achievements, she remains a relatively obscure figure. The reason for this is not hard to find. For, remarkable as it was, Caroline Herschel’s life has been largely overshadowed by that of her brother, William - discoverer, in 1781, of the planet Uranus. As William Herschel’s assistant and amanuensis, Caroline might also be said to have contributed to this discovery, and to others that followed, such as the discovery of infra-red radiation. However, the fact remains that, when her existence is acknowledged at all, she is often dismissed as no more than a diligent ‘helpmeet’ - a facilitator of scientific discoveries, rather than a discoverer in her own right.
So who was Caroline Herschel? Born in Hanover in 1750, the eighth child of ten, to an impoverished musician and his wife, Caroline can hardly have been said to have had an auspicious beginning. Smallpox, at the age of four, left her (as she laconically remarked) ‘totally disfigured’; an outbreak of typhus, some years later, nearly killed her. Her childhood was harsh – denied the musical education from which her brothers benefited, she was assigned the role of household drudge, terrorised over by her elder brother, Jacob. And yet her memories of this grim time were not entirely unhappy. In her journal, she recalls a winter’s walk with her father:
I remember his taking me in a clear frosty night in the street to make me acquainted with some of the most beautiful constellations, after we had been gazing at a Comet which was then visible…
A significant moment, no doubt, for the future astronomer.
Rescued from her unrewarding existence by her brother William, who was then working as Director of the Bath Choir, the twenty-two year-old Caroline found herself in England. Here, at William’s insistence, she was to train as a professional singer. From this time on, she divided her time between practising ‘5, 6 hours at the Harpsichord’ every day, and assisting her brother in his new enthusiasm – for astronomy. Over the next few years, Caroline built up a considerable reputation as a soloist, often singing lead soprano in one of the Handel operas or oratorios, which were then all the rage. But her musical career was not to last. With the discovery, by William, in 1781, of what turned out to be a new planet, ‘Georgium Sidus’ (Uranus), the Herschel siblings’ peaceful existence in Bath came to an end. Overnight, William became internationally famous, and was conscripted by George III to act as his personal astronomer. Caroline, much against her will, was obliged to abandon her music ‘to be trained for an assistant Astronomer’. In this capacity (she wrote)
I was to sweep for Comets, and… write down and describe all remarkable appearances I saw in my Sweeps…
But it was not till the last two months of the same year before I felt the least encouragement for spending the starlight nights on a grass-plot covered with dew or hoar frost without a human being near enough to be within call…
The telescopes used were enormous - twenty-foot Newtonian instruments with twelve-foot mirrors, mounted on specially constructed wooden scaffolds, with ladders to enable the astronomer and his faithful assistant to scramble up and down at will. They needed frequent adjustment, and this was not without its hazards. One night, working, as was usual, in the cold and dark, Caroline was badly injured when attempting to carry out such an adjustment. William, who was perched on a ladder at the front of the telescope, shouted an instruction to his sister to alter the position of the instrument. In running to obey his command, Caroline slipped on a patch of melting snow, and fell onto one of the iron hooks tethering the guy-ropes attached to the scaffold. It ‘entered my right leg about 6 inches above the knee,’ she wrote, with typical sang froid. ‘My brother’s call, “Make haste!” I could only answer by a pitiful cry of “I am hooked!”…’
Fortunately, she recovered from the injury - whose effects, in those days before penicillin, were perhaps mitigated by the extreme cold. And those late-eighteenth century winters were very cold indeed. It was not unusual for the ink to freeze in the inkwell on Caroline’s desk, in the hut where she sat, each night from ten or twelve until three or four in the morning, recording the night’s observations.
In spite of the discomforts (and occasional hazards) of her new life, Caroline soon became as enthusiastic about star-gazing as her brother. Provided by William with a purpose-built ‘sweeper’ for detecting comets, she began at once to find them.
I have calculated 100 nebulae today
she wrote in her journal on 1st August, 1786
and this evening I saw an object which I believe will prove to morrow night to be a Comet…
It did indeed prove to be a comet. Caroline wrote that evening to the Royal Society, to announce her discovery. And for a brief but heady period, she enjoyed the fame which had, up until then, been her brother’s exclusive preserve. Not only the President and Secretary of the Royal Society, but also Lord Palmerston, and later, the King and Queen, came to the Herschels’ home at Slough in order to view the comet. The novelist Fanny Burney was also present on one of these occasions. ‘The comet was very small,’ she wrote, ‘and had nothing grand or striking in its appearance; but it is the first lady’s comet, and I was very desirous to see it…’
Nor was this the last such excitement Caroline’s new life as an astronomer was to offer. While her brother occupied himself with building still more enormous telescopes - a forty-foot monster was constructed in the grounds of the house in Slough, in 1787 - Caroline got on with what she was good at, which was finding comets. Here is an account of Caroline’s working practises, as described in a letter written in 1793, by Nevil Maskelyne, a great friend of both the Herschels:
I paid Dr & Miss Herschel a visit 7 weeks ago. She shewed me her 5 feet Newtonian telescope made for her by her brother for sweeping the heavens. It has an aperture of 9 inches, but magnifies only from 25 to 30 times… being designed to shew objects very bright, for the better discovering any new visitor to our system, that is Comets, and any undiscovered nebulae. It is a very powerful instrument, & shews objects very well… The height of the eye-glass is altered but little in sweeping from the horizon to the zenith. This she does in 6 or 8 minutes, & then moves the telescope a little forward in azimuth, & sweeps another portion of the heavens in like manner. She will thus sweep a quarter of the heavens in one night.
The Astronomer Royal’s admiration seems to have been reciprocated. In August 1797, a few years after the visit described above, Caroline found her eighth - and, as it turned out, final - comet. After a night’s observing, and no doubt very little sleep, she saddled a horse and rode the thirty miles from Slough to the Royal Astronomer’s house at Greenwich, in order to ensure that Maskelyne would be the first to hear of her discovery. Glimpses such as this give one a sense of the extraordinary determination of the woman. Her journals and letters also reveal a dry wit. Replying to a letter from Maskelyne, in which he had praised her work on the Index to Flamsteed’s Catalogue - another of her by no means negligible achievements - she said:
Your having thought it worthy of the press [that is, of publication] has flattered my vanity not a little. You see, sir, I do own myself to be vain, because I would not wish to be singular; and was there ever a woman without vanity? Or a man either? Only with this difference, that among gentlemen the commodity is generally styled ambition.
Caroline was still only in her early forties. She was to live for another fifty years. For her work in producing the Index to Flamsteed’s Catalogue, she was to be made an Honorary Member of the Royal Astronomical Society in 1835 - one of the first two women to be so honoured (the other was Mary Somerville); although it would be another eighty years before Girton’s Annie Scott Dill Maunder would be elected the first female member of the RAS. Although she was never to marry, Caroline enjoyed close friendships with some of the most fascinating men and women of the age. She was a devoted sister, and an adoring aunt to her brother’s only son, John - who also became an astronomer, and whose cataloguing of the southern skies completed what his father and aunt had achieved in the northern hemisphere.
So: it is time for Caroline Lucretia Herschel to come out of her brother’s shadow and take her rightful place in the history of science? I certainly think so - and I can’t help feeling that the extraordinary events of last Wednesday might never have happened at all had it not been for the pioneering efforts of Caroline Herschel and others like her - the unsung sisterhood of science.