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Caroline was continuing her singing training, and beginning to perform regularly in Herschel’s concerts at the Pump Room. But she ‘could not help feeling some uneasiness’, as she put it, about her future prospects, as more and more of William’s time was ‘filled up with Optical and Mechanical works’.
(#litres_trial_promo) Once they went together to fulfil a singing engagement in Oxford, but Caroline remembered it largely for the perilous journey home, ‘for the jaunt was made in a single horse Chaise, and my Brother was not famous for being a good driver’.
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Then William gave her ten guineas-a very considerable sum-to spend on whatever evening dress she liked, for her musical performances. She was overjoyed when the proprietor of the Bath Theatre, Mr Palmer, solemnly pronounced her to be ‘an Ornament to the Stage’, a compliment she never forgot.
(#litres_trial_promo) On 15 April 1778 she was advertised, for the first time, as the principal solo singer in a programme of selections from Handel’s Messiah at the Bath New Rooms. As this was Herschel’s own end-of-season ‘Benefit Concert’, it was clearly he who promoted her. Her performance was such a success that she was offered her first solo professional engagement by a company at the Birmingham Festival for the following spring. Here at last was her chance of an independent career, at the age of twenty-eight. But after consultation with William, she turned it down, announcing that she was ‘resolved only to sing in public where her brother was conducting’. Consciously or not, she had made a decision about her future with William.
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It may be no coincidence that the following year, 1779, Herschel began a much more serious and regular pattern of observations. He recorded: ‘January. I gave up so much of my time to astronomical preparations that I reduced the number of my [music] scholars so as not to attend more than 3 or 4 a day.’
(#litres_trial_promo) He had decided on his first major astronomical project: to establish a new catalogue of so-called ‘double stars’.
John Flamsteed had observed over a hundred double stars, but had established no special record of them, and there were obviously many more to be found. The value of double stars was that they might provide a method of gauging the earth’s distance from the rest of the Milky Way, by the measuring of parallax.
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Although distances within the immediate solar system-to the moon and notably to the sun (using the Transit of Venus observations)-had been approximately measured, there was no general idea how far away the stars were, or what the size of the Milky Way might be. Kant, for example, assumed that Sirius (the Dog Star), because of its brightness, was probably the centre of the entire Milky Way galaxy, and possibly of the whole universe.
(#litres_trial_promo) In fact it is one of our nearest stars, just over 8.7 light years away.
Most current ideas about the cosmos were small-scale. It was widely believed that the earth was a few thousand years old at most (Biblical calculations gave 6,000 years), and that the universe might stretch out a few million miles ‘above’ the earth. The ‘fixed stars’ revolved in an unchanging pattern, and their brightness or magnitude was probably a function of their size, rather than their distance. So a faint star was probably comparatively small, rather than comparatively far away-a perfectly reasonable assumption. (One of Herschel’s most simple and radical ideas was to assume exactly the opposite.) The physical closeness of the stars and planets also explained their astrological ‘influences’. The universe was small, closely connected, largely unchanging (except for comets), and almost intimate.
Nevertheless, the eighteenth century had been rich in speculative theories about the possibility of a ‘Big Universe’. These included Thomas Wright’s Original Theory or New Hypothesis of the Universe (1750) and Kant’s Universal Natural History of the Heavens (1755), which first proposed-though without observational evidence-that there might be ‘island universes’ outside the Milky Way, that some distant stellar systems might be altering, and that the whole cosmos might be in some sense ‘infinite’, though it was not clear what exactly ‘infinite’ might mean, as hitherto it was a quality possessed only by God and mathematics. Herschel himself had added to these theoretical accounts with an early paper, eventually published by the Bath Philosophical Society, ‘On the Utility of Speculative Enquiries’.
All these speculative essays assumed the high probability that extraterrestrial life existed, either within the immediate solar system, or further out among the stars. James Ferguson, for example, stated in the opening of his Astronomy Explained (1756) that the entire universe was evidently populated, if not positively crowded, with living forms: ‘Thousands upon thousands of Suns…attended by ten thousand times ten thousand Worlds…peopled with myriads of intelligent beings, formed for endless progression in perfection and felicity.’
(#litres_trial_promo) It was further assumed that such life forms, though not necessarily human in appearance, would have developed civilisations and sciences superior to our own. The question of whether they were ‘fallen’ in a religious sense, and required Redemption according to Christian doctrine, remained a moot point among astronomers, few of whom would have considered themselves as ‘atheists’ in any modern sense. ‘An undevout astronomer is mad,’ as the poet Edward Young reflected in Night Thoughts (1742-45).
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However, the growing sense of the sheer scale of the universe, and the possibility that it had evolved over unimaginable time, and was in a process of continuous creation, did slowly give pause for thought. For a poet like Erasmus Darwin, in The Botanic Garden (1791), it put the Creator at an increasing shadowy distance from his Creation.
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This interest in extraterrestrial life was one of the reasons that Herschel remained so fascinated by the surface of the moon, with its mysterious mountains and craters, and dramatically shifting patterns and colours of shadow. When it was invitingly at the crescent (the best time to study surface detail), but too low to be observed from his tiny back yard, he would take his seven-foot telescope out into the cobbled street in front of the house. So it was, in December 1779, while Herschel was ‘engaged in a series of observations on the lunar mountains’, that a passing carriage stopped, a young gentleman sprang out, and he had his first historic meeting with Dr William Watson, junior. This was Herschel’s first really important scientific contact in England, one not made until he was forty-one. Watson was only thirty-three.
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Herschel later recalled the moment with appropriate gravity: ‘The moon being in front of my house, late in the evening I brought my seven-foot reflector into the street…Whilst I was looking into the telescope, a gentleman coming by the place where I was stationed, stopped to look at the instrument. When I took my eye off the telescope, he very politely asked if he might be permitted to look in…and expressed great satisfaction at the view. Next morning, the gentleman, who proved to be Dr Watson, junior (now Sir William), called at my house to thank me for my civility in showing him the moon.’
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Caroline remembered it rather less formally. Herschel and Watson were so immediately taken with each other that very night that they burst into the house and began ‘a conversation which lasted until near morning; and from that time on [Dr] Watson never missed to be waiting on our house against the hours he knew my Brother to be disengaged’.
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Watson warmly befriended Herschel, and encouraged his work even to the extent of helping with pounding horse-dung moulds and casting speculum mirrors. He quickly became what Caroline called ‘almost an intimate of the family’.
(#litres_trial_promo) He had Herschel elected to the Bath Philosophical Society as ‘optical instrument maker and mathematician’ (no mention of musician), and over the next two years encouraged him to submit no fewer than thirty-one papers at its meetings. These included ‘On the Utility of Speculative Enquiries’, ‘On the Existence of Space’, and further unconventional observations on the moon. They are evidence of the extraordinary intellectual ferment that had seized upon Herschel.
His notion of the cosmos was already far from conventional, and several of these papers were what would now be called ‘thought experiments’. In his ‘Space’ paper, delivered on 12 May 1780, he astonished his audience with his radical thoughts on time and distance: ‘Huygens said that it was possible some of the fixt Stars might be so far off from us that their light tho’ it travelled ever since the Creation at the inconceivable rate of 12 million of miles per minute, was not yet arrived to us. The thought is noble and worthy of a Philosopher. But [should] we call this immense distance a mere imagination? Can it be an abstract Idea? Is there no such thing as space?’
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In the case of his moon speculations, he raises the question whether a scientific idea has to be ‘correct’ to be significant. One of Herschel’s most ingenious ideas was that moon craters were artificially constructed circular cities (or ‘Circuses’), built especially to harness solar power for the lunar inhabitants: ‘There is a reason to be assigned for circular Buildings on the Moon, which is that as the Atmosphere there is much rarer than ours and of consequence not so capable of refracting and (by means of clouds shining therein) reflecting the light of the Sun, it is natural enough to suppose that a Circus will remedy this deficiency. For in that shape of Building one half will have the direct, and the other half the reflected, light of the Sun. Perhaps, then on the Moon every town is one very large Circus?’
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So, besides the two main projects, to record all new double stars and all new nebulae, Herschel was also embarked on a third and partly secret programme in 1779: to discover life on the moon. For some time he did not risk sending this section of the lunar paper to Maskelyne at the Royal Society, but both Watson and Caroline were aware of it. This was one of the reasons he needed to construct better telescopes.
The moon project had begun with a long entry made in his Observation Journal for 28 May 1776. He saw ‘what I immediately took to be woods or large quantities of growing substances in the Moon’. With a certain angle of solar light, some of the lunar shadows looked like ‘black soil’ spread down a mountainside. Other puzzling stippled shadows, especially in the Mare Humorum, Herschel believed were enormous ‘forests’, made up of huge, spreading leafy canopies, or at least ‘large growing substances’. Because of low lunar gravity, this gigantic ‘vegetable Creation’ was evidently ‘of a much larger size on the Moon than it is here’.
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Similarly, he tended to believe that there were so many of the smaller moon craters that they must be artificial constructions: ‘By reflecting a little on this subject I am almost convinced that those numberless small Circuses we see on the Moon are the works of Lunarians and may be called their Towns.’ Nonetheless, true science required not speculation but accurate observation and telescopic proof. ‘But this is no easy undertaking to make out, and will require the observation of many a careful Astronomer and the most capital Instruments that can be had. However this is what I will begin.’
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The light-gathering power of Herschel’s seven-foot reflector allowed him to see many objects that no previous astronomers had accurately observed, or at least recorded. With Caroline taking notes at his dictation, they began to compose a new catalogue of double stars, and to develop a system of recording the exact time and position of any unusual stellar phenomena not previously catalogued by Flamsteed. By this means Herschel began to build up an extraordinary, instinctive familiarity with the patterning of the night sky, which gradually enabled him to ‘sight-read’ it as a musician reads a score. He would later himself use such musical analogies to explain the technique and art of observation.
In early 1781 it was decided to close down the millinery business at 5 Rivers Street. William and Caroline moved back to the substantial three-storey terraced house at 19 New King Street, where the telescope equipment was immediately set up in the fine little back garden: ‘beyond its walls all [was] open as far as the river Avon’. Here, as Caroline noted modestly, ‘many interesting discoveries were made’. At first she however had to remain at Rivers Street to oversee the selling off of the linen stock, and she missed the first few nights of observation in March. She subsequently recorded, with unusual care, that she did not return to New King Street until 21 March-as it turned out a historic absence.
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During these nights around the spring equinox Herschel was observing alone, and as well as continuing with their catalogue of double stars, he gave himself up to making drawings of Mars and Saturn. Possibly he was ranging more freely than usual, or possibly he was testing his ability to ‘sight read’ the sky. At all events, on Tuesday, 13 March 1781, slightly before midnight, Herschel spotted a new and unidentified disc-like object moving through the constellation of Gemini. This discovery would change his entire career, and become one of the legends of Romantic science.
It also raises an intriguing question: how soon did Herschel know-or suspect-what he had discovered? It seems from his Observation Journal at the time, that what he thought he had found was a new comet. The following laconic account appears in his ‘First Observation Book’ for 12 and 13 March 1781
March 12 5.45 in the morning. Mars seems to be all over bright but the air is so frosty & undulating that it is possible there may be spots without my being able to distinguish them. 5.53 I am pretty sure there is no spot on Mars. The shadow of Saturn lays at the left upon the ring.
Tuesday March 13 Pollux is followed by 3 small stars at about 2’ and 3’ [minutes of arc] distance. Mars as usual. In the quartile near Zeta Tauri the lowest of two is a curious either nebulous star or perhaps a Comet. A small star follows the Comet at 2/3rds of the field’s distance.
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There are no further remarks for these nights, and certainly no expression of excitement or anticipation. On the following night, Wednesday, 14 March, it was either cloudy, or Herschel did not bother to observe, for there is no entry. He may have been prevented by an official engagement to play the harpsichord at the Bath Theatre, or to rehearse oratorios with Caroline.
(#litres_trial_promo) On 15 March there are short observations on Mars and Saturn, accompanied by some drawings of them made between 5 and 6 a.m., but nothing further about the ‘curious nebulous star or comet’. On Friday, 16 March there is again no entry. But Herschel may have been reflecting on his sightings, and talking to Caroline over the weekend, for finally, on the night of Saturday, 17 March there is the first clear sign that he was definitely in pursuit of the mysterious new object.
Saturday March 17 11pm. I looked for the Comet or Nebulous Star and found that it is a Comet, for it has changed its place. I took a superficial measure 1 rev, 6 parts and found also that the small star ran along the other [cross] wire…Position exactly measured 91′96…
Once Caroline had returned to New King Street on the twenty-first, there are regular entries in late March following the ‘comet’, and attempts to measure its diameter with William’s newly designed micrometer. For example, on 28 March the Observation Book reads: ‘7.25 pm. The diameter of the Comet is certainly increased, therefore it is approaching.’
(#litres_trial_promo) The increase in apparent size was a further indication of ‘proper motion’ and a solar orbit; and further proof that it could not possibly be a fixed star. But if it was a comet, there should be a slightly blurred, fiery outline and a distinct tail or ‘coma’. Here Herschel’s beautifully clear reflector images, even more than his high-magnification eyepieces, came into their own. In early April, some three weeks after his first sighting, Herschel made what seemed to be a definitive observation.
Friday April 6 I viewed the Comet with 460 [magnifications] pretty well defined, no appearance of any beard or tail. With 278 [magnifications] perfectly sharp and well defined.
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Though Herschel was scrupulously careful not to say so in his Observation Book, the sharp, round definition and the lack of any tail could only mean one thing: a new ‘wanderer’, or planet. What in fact he had observed was the seventh planet in the solar system, beyond Jupiter and Saturn, and the first new planet to be discovered for over a thousand years (since Ptolemy). He would name it patriotically after the Hanoverian king, ‘Georgium Sidus’ (‘George’s Star’), but it eventually became known to European astronomers as Uranus. ‘Urania’ was the goddess of astronomy, and the new planet was seen to mark a rebirth in her science.
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Yet there was no Eureka moment: quite the opposite. For the next few weeks there was a great deal of uncertainty about what sort of astronomical body Herschel had found. Nowhere does the word ‘planet’ appear in his Observation Journal for that spring of 1781, and there was no popular reporting of the news in the magazines. The following year, when the sensation was widely known, it would be very different, as Caroline remarked: ‘Since the discovery of the Georgium Sidus, I believe few men of learning or consequence left Bath before they had seen and conversed with its discoverer.’ But for the time being there were just endless measurements with the micrometer, ‘and a fire to be kept in, and a dish of Coffee during the long nights of watching’. She added wryly: ‘I undertook with pleasure what others might have thought a hardship.’
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On 22 March Herschel tentatively communicated his preliminary observations of ‘a Comet’ to William Watson, who passed them on to Nevil Maskelyne and Joseph Banks at the Royal Society.
(#litres_trial_promo) Maskelyne immediately contacted other European astronomers, notably Charles Messier in Paris, asking for their opinion.
(#litres_trial_promo) A week later Herschel followed this up with a direct report to the Royal Society, which was logged in the Society’s ‘Copy Journal Book’ for 2 April. Now he expressed barely muted excitement: ‘Saw the Diameter of the Comet extremely well defined and distinct; with several different powers thro’ my 20 foot Newtonian reflector. It was a glorious sight, as the Comet was placed among a great number of small fixt stars that seemed to attend it.’
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Remembering Herschel’s ‘lunacies’ of the previous year, Maskelyne was initially sceptical. He found great difficulty in even locating the new object with his own telescopes at Greenwich, a difficulty increased by Herschel’s inability to provide the conventional mathematical coordinates. At this stage Herschel located all his stars on hand-drawn star maps-what he called ‘an eye-draught’-an amateur technique that again visually recalls his familiarity with musical scores.
(#litres_trial_promo) It was not until 4 April that Maskelyne wrote cautiously to Watson (still not to Herschel directly) that he had finally found the new ‘star’, and observed that it had just discernible ‘motion’. However, he prudently, and not unreasonably, hedged his bets: ‘This [the motion] convinces me it is a comet or a planet, but very different from any comet I ever read any description of or saw. This seems a Comet of a new species, very like a fixt star; but perhaps there may be more of them.’ This safely covered all the options. He added a pointed postscript: ‘PS I think [Herschel] should give an account of his telescope, and micrometers.’
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The Astronomer Royal was in a dilemma. He had no reason to accept Herschel as a reliable astronomer, and to declare a new planet prematurely might bring himself and the Royal Society into disrepute, and even ridicule. On the other hand, to reject what might be the greatest British astronomical find of the century, especially if the predatory French astronomers accepted it first (and even named it), would be even more damaging. He was also aware that Banks regarded this as a crucial moment in his presidency, and in the fostering of good relations between the Royal Society and the Crown. King George III was particularly fascinated by stars, and particularly keen to outdo the French.
Maskelyne finally chose to act as a man of science: he went back to his own telescopes, and from 6 to 22 April made his own observations. He was, after all, acting precisely according to the motto of the Royal Society itself: Nullius in Verba-‘Nothing upon Another’s Word’. On 23 April he at last wrote directly to ‘Mr William Herschel, Musician, near the Circus, Bath’. He began prudently, but ended firmly.
Greenwich Royal Observatory, April 23, 1781
Sir, I am to acknowledge my obligation to you for the communication of your discovery of the present Comet, or planet.
I don’t know which to call it. It is as likely to be a regular planet moving in an orbit nearly circular round the sun, as a Comet moving in a very eccentric ellipsis. I have not yet seen any coma or tail to it…
This tipped the argument towards a planet, but was not a decisive opinion. Maskelyne then went into technical details about their respective telescopes-especially the need for ‘very firm stands’-and the difficulties of using micrometers to measure apparent changing diameters (and hence establish a possible planetary orbit): ‘If the light of the small planet is not still, & free from scintillations, it is impossible to prove it to have any other than a spurious diameter that may arise from the faults to which the best telescopes are subject.’ Nonetheless, he praised Herschel for making ‘very good observations’.
Finally, in his last paragraph, he committed himself. ‘On the 6th April I viewed the Comet with my 6 foot reflecting telescope and the greatest power 270, and saw it a very sensible size but not well defined. This however showed it to be a planet and not a fixt star, or of the same kind of fixt stars as to possessing native light with an insensible diameter. I am Sir, etc etc, N. Maskelyne.’
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Herschel had gained an invaluable ally. He immediately sent up a brief, masterly paper which was read at the Royal Society on 26 April. It was entitled simply ‘An Account of a Comet’, and was published in the Philosophical Transactions in June. He stated that ‘between ten and eleven in the evening’ of 13 March 1781 he had at once recognised a new object of ‘uncommon magnitude’ in Gemini, and immediately ‘suspected it to be a comet’. But from the account he then gave of its magnitude, clarity of outline and ‘proper motion’ it was clear that Herschel was now claiming that the ‘comet’ was really a new planet. Though, no doubt advised by Watson, he did not actually say so. To support this, he also claimed that the object remained perfectly round, without the least appearance of comet’s tail, when magnified 270, 460 and 932 times-the latter magnifications being far beyond what even Maskelyne’s Greenwich telescopes could achieve. All this naturally excited even more controversy than his moon paper, and some murmurs of dissent.
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Maskelyne nevertheless stoutly confirmed his opinion to Banks that their dark horse, the ‘musician of Bath’, had made a revolutionary discovery, and had ‘much merit’. Yet he could not suppress a touch of rueful irony. ‘Mr Herschel is undoubtedly the most lucky of Astronomers in looking accidentally at the fixt stars with a 7 foot reflecting telescope magnifying 227 times to discover a comet of only 3’ [seconds of arc] diameter, which if he had magnified only 100 times he could not have known from a fixt star…Perhaps accident may do more for us than design could; and this makes one wish that the number of astronomers was multiplied in order to increase our chance of new discoveries.’
(#litres_trial_promo) This suggestion that the discovery had been ‘accidental’, and that he had been ‘lucky’, was to grow increasingly disturbing to Herschel.
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Maskelyne had made public his support of Herschel just in time. On 29 April Messier wrote directly to ‘Monsieur Hertsthel at Bath’ from Paris, congratulating him-‘this discovery does you much honour’-and giving his opinion that this was very likely to be the seventh planet in the solar system. Messier had himself, he said modestly, discovered no fewer than eighteen comets in his lifetime, and this resembled none of them: it was ‘a little planet with a diameter of 4 to 5 seconds, a whitish light like that of Jupiter, and having the appearance when seen with glasses of a star of the 6th magnitude’. He signed ‘with consideration and respect’ as ‘Astronomer to the Navy of France, of the Academy of Sciences, France’.
As Maskelyne and Banks were only too aware, Messier’s congratulations would soon carry the weight of the entire French Académie des Sciences.
(#litres_trial_promo) Throughout the spring and summer months of 1781, more and more astronomers-in France, Britain, Germany, Italy and Sweden-observed the tiny moving speck, and took the view that it was indeed a planet circling in a massive ellipse beyond Saturn. These included Jacques Cassini, Henry Cavendish and Pierre Méchain. In October Anders Lexell, the celebrated Russian mathematician, wrote from his observatory far away in St Petersburg, sending a fully computed orbit and adding his congratulations. Using a series of parallax readings, he calculated that the planet was large and unbelievably remote, over sixteen times further from the sun than the earth, and twice as far out as Saturn. The size of the solar system had been doubled. Jérôme Lalande, who also computed the orbit, later said that this was the moment when the Académie des Sciences finally accepted the new planet-seven months after it had been sighted. Lalande himself suggested it should be christened ‘Herschel’.
It is suggestive that it was mathematical calculation, rather than astronomical observation, which finally convinced the scientific community that a seventh planet really did exist. One of the things Lexell’s calculation showed was that Herschel’s vivid impression that the planet was increasing in apparent diameter throughout March and April (and therefore approaching the earth) must have been the product of his growing concentration and excitement, since it was actually getting smaller and moving away. Lexell continued to work patiently for several years on his calculations, and later came up with the revised figure of 18.93 times the distance from the earth, impressively close to the modern computer-generated figure of 19.218. (In fact, as the planet’s orbit is elliptical not circular, the distance varies: at its closest it is 18.376 and at its furthest it is 20.083.)
In May, Watson proudly took Herschel up to London to meet his father Sir William, and to renew his now extremely cordial relations with Nevil Maskelyne. Together with the wealthy Deptford astronomer Alexander Aubert, they all dined with Sir Joseph Banks at the Mitre Club, the tavern much favoured by Dr Johnson. This was Herschel’s first meeting with the inner circle of British astronomers, and it was a great success. There was an air of suppressed triumph and excitement. Banks, in high spirits, seized his hand, congratulated him on ‘the great discovery’, and announced that he was to be elected to the Royal Society and awarded the Copley Gold Medal forthwith-within the next fortnight!
(#litres_trial_promo) He claimed it as a decisive British victory over French astronomy, and the eminence of Messier, Pierre Laplace and Lalande, who had hitherto dominated European astronomy.
In fact Banks’s enthusiasm had rather got the better of him. The Copley Medal and the fellowship election had to go through the Society’s plodding bureaucratic procedures, which took another six months. Maskelyne used the interval to write warmly to Herschel in August: ‘I hope you will do the astronomical world the favour to give a name to your new planet, which is entirely your own, and which we are so much obliged to you for the discovery of.’
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It was subsequently shown that ‘Georgium Sidus’ had actually been observed and recorded at least seventeen times between 1690 and 1781, and was even catalogued by Flamsteed. But it had always been dismissed as a minor ‘fixed’ star. It was only Herschel’s observational genius-and the quality of his seven-foot reflector-which identified it as a large, steadily moving body in regular orbit round the sun: a true planet. And it was Maskelyne who, by promptly supporting Herschel and bringing his observations to the attention of other leading European astronomers, confirmed the discovery and had it accepted by the scientific community at large. It later became clear that Uranus was a weird blue ice giant (not ‘little’ as Messier thought), twice the distance of Saturn, and taking 84.3 years to complete a solar orbit. It is the only planet in the solar system which is tilted ‘on its side’, so its axis of rotation, or spin, is horizontal to its solar orbit.
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In November Banks wrote a friendly and characteristically droll letter to Herschel, asking him for details of how he made the discovery that famous night, and all the difficulties ‘etc etc’ it caused him. He wanted to refer to these when presenting him to the assembled members of the Royal Society in London the following month: ‘Sir, The Council of the Royal Society have ordered their Annual Prize Medal to be presented to you in reward for your discovery of the new star. I must request that (as it is usual for me on that occasion to say something in commendation of the discovery) you will furnish me with such anecdotes of the difficulties you experienced etc etc…as you may think proper to assist me in giving due praise to your industry and ability.’
Banks, in high good humour, also enjoyed putting Herschel on his mettle. ‘Some of our astronomers here incline to the opinion that it is a Planet, and not a Comet. If you are of that opinion, it should forthwith be provided with a name, or our nimble neighbours, the French, will certainly save us the trouble of Baptizing it.’
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Herschel, again advised by Watson, asked Banks if he could name the planet after the King, ‘Georgium Sidus’, a sound and self-effacing diplomatic stroke from a fellow Hanoverian.
(#litres_trial_promo) But he was less easy about the continuing murmurs in some quarters of the Royal Society that his discovery had been in some sense ‘accidental’. This struck at his very notion of scientific method. He wrote insistently, even angrily, to Banks just before the ceremony on 19 November: ‘The new star could not have been found out even with the best telescopes had I not undertaken to examine every star in the heavens including such as are telescopic, to the amount of at least 8 or 10 thousand. I found it at the end of my second review after a number of observations…The discovery cannot be said to be owing to chance only it being almost impossible that such a star should escape my notice…The first moment I directed my telescope to the new star, I saw with a power of 227 that it differed sufficiently from other celestial bodies; and when I put on the higher powers of 460 and 932 was quite convinced it was not a fixt star.’
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This claim was to become a point of honour with Herschel, often repeated. In September 1782 he wrote to Lalande in Paris, stating emphatically that the discovery ‘was not owing to chance’. Since he was embarked on a regular review of the sky, ‘it must sooner or later fall into my way, and as it was that day the turn of the stars in that neighbourhood to be examined, I could not very well overlook it’.
(#litres_trial_promo) The following year he wrote to the German astronomer Georg Christoph Lichtenberg at Göttingen, repeating that it was ‘not by accident’, and adding: ‘when I came to Astronomy as a branch of [mathematics] I resolved to take nothing upon trust but see with my own eyes all what other men had seen before’.
(#litres_trial_promo) Lichtenberg replied enthusiastically (in German): ‘Mein Gott! If I had only known, when I was for a few days in Bath in October 1775, that such a man lived there! As I am no friend of tea rooms, nor of cards or balls, I was much ennuyéd and spent my time at the top of the [cathedral] tower with a field glass…’
When he came to write an autobiographic sketch for his friend Dr Hutton in 1809, Herschel was more insistent than ever: ‘It has generally been supposed that it was a lucky accident which brought this star to my view; this is an evident mistake. In the regular manner I examined every star of the heavens, not only of that magnitude but many far inferior, it was that night its turn to be discovered. I had gradually perused the great Volume of the Author of Nature and was now come to the seventh Planet. Had business prevented me that evening, I must have found it the next, and the goodness of my telescope was such that I perceived its planetary disk as soon as I looked at it; and by application of my micrometer, I determined its motion in a few hours.’
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This claim is not entirely borne out by his original Observation Journal. His first sweep or ‘review’ of double stars, begun in 1779, had not revealed the Georgium Sidus, so discovery on the second was not inevitable. Nor was recognition instant when it came. The journal reveals no precise Eureka ‘first moment’ on 13 March, only the hardening suspicion drawn out over five days to Saturday, 17 March that the strange body had ‘proper motion’, but was neither a ‘nebulous star’ nor a ‘comet’, and so was very probably a new planet. But it was Nevil Maskelyne who was the first to say so explicitly in writing, in April.
Nevertheless, Herschel’s discovery was an astonishing feat. It became his professional signature, and a historic moment for cosmology. It is hardly surprising that over the years he continued romantically to refine the story, and compressed his discovery into a single wondrous night, the inspired work of a glorious ‘few hours’. Caroline never commented on this, although it seems clear that she was present during the critical nights of measuring between 21 March and 6 April 1781. The effect of this account was to present an engagingly romantic image of science at work: the solitary man of genius pursuing the mysterious moment of revelation.
