George Biddell Airy Astronomer Royal

Young George was not popular with his classmates at school because, he said, he had very little "animal vitality." He was also snobbish and conceited. But his classmates endured him when he created useful gadgets for mischief such as peashooters.

At the age of 12, George, already concerned for his own advancement, conspired with his mother's brother, a wealthy and well-educated farmer, to adopt and hide him from his family without informing them so that he would have better social contacts. His father, depressed over the loss of his job with the tax office, declined to block the arrangement.

At the age of 18, Airy was off to Cambridge University with a scholarship and a very high opinion of himself. He made no friends, and professors judged his abilities to be limited, but Airy worked doggedly and carried off the two big science and mathematics prizes as senior wrangler and First Smith's prizeman in 1823. He thought well enough of himself by this time to write his first autobiography.

Just as meticulously as he recorded his younger days, so he carefully plotted his future life. He kept a complete daily record of his activities aid thoughts. His financial accounts were personal kept by double entry throughout his life, and hi regarded their keeping as one of his greatest joji' He never destroyed a document and preserved^ his old checkbook stubs, bills, and receipts free merchants in chronological order. A colleague i Cambridge quipped, "if Airy wiped his pen oui piece of blotting-paper, he would duly endorse the blotting-paper with the date and particulars of te use, and file it away amongst his papers."1 1 As a fellow of TVinity College in 1824, he sethis sights on the position of astronomer royal ami refused to accept an assistantship at the Roys! Observatory because assistants had not previously been promoted to the post. Instead he fought his way upward through professorships at CambrMji campaigning successfully for higher pay. In 183;

'George Biddelt Airy. Autobiography, edited by Wilfrid Airy iCuttrif Al the University Press, 1896|. p. 2.

2This story, told by Augustus De Morgan, appears in E. Walter V-wato The Koyal Observatory QrccuwkJi |Luiiduu. Religiuu» 1V*c! I900|, pp. 116-117.

because of his clear, enthusiastic, and engaging way of explain-the Pu was popular with astronomers because he liked to iden-

¡ng sciences scientific problems and pass them along to young ers for solution. He would then encourage and assist them with aStr0D • ht and his encyclopedic knowledge of the scientific literature.

He Ï? helped to find them jobs. I the summer of 1845, Arago urged Urbain Jean Joseph Le Verrier ake on the problem of the motion of Uranus. Arago was a shrewd ■°H of talent who could pair the scientific difficulty of a problem with Ihe1intellectual capability of a scientist. Le Verrier, like Adams, had come from a family of modest means in rovinces. He was born in Saint-Lô in Normandy on March 11, 1811. His father an estate manager, did all he could to foster his son's intellectual ursuits, and Urbain responded by reaching the top of his class at high school in Caen. He then took the highly competitive exam for the École Polytechnique in Paris, but there were gaps in his provincial education

Urbain Jean Joseph Le Verrier

Royal Greenwich Observatory

Urbain Jean Joseph Le Verrier

Royal Greenwich Observatory

George Biddell Airy, astronomer royal national Maritime Museum Greenwich

he received the call he expected as the seventh astronomer royal. He immediately set to work restructuring the Royal Observatory in his mold. Airy was an organizer rather than a scientist.1

I Eggen. "George Biddell Airy " DtrHoniry Ringrttphy

¡New York; Claries Scribner's Sons. 1974|.

Under his direction the Royal Observatory was a superb servant of the Navy, providing tables for celestial navigation of improved precision. Greenwich expanded into meteorological and magnetic record keeping. But among staff members, Airy tolerated no independent thought or research. Observers were often required to work 21 hours straight. Young boys hired to do arithmetic calculations were kept at their desks for 12-hour shifts with no breaks except for one hour at midday. Morale was poor. But Airy's efficiency and discipline at the Royal Observatory were admired in England and copied by many other countries, which led years later, particularly in England, to a conspicuous lack of creativity in observational astronomy.

Airy declined knighthood three times, complaining about the initiation fees and the cost of maintaining the expected life-style, but finally accepted the honor in 1872. He retired as astronomer royal in 1881 at the age of 80 and spent his remaining ten years filing (but not organizing the contents of) his papers.

François Arago, director of the Paris Observatory

Royal Greenwich Observatory

François Arago, director of the Paris Observatory

Royal Greenwich Observatory and he was not admitted. Urbain's father thereupon sold the family J for cash to enroll his son in the Collège de Saint Louis in Paris for

3 'oraij tional preparation in 1830. Urbain rewarded his father's sacrifirJ winning the annual mathematics prize sponsored by the École FbiyZS nique in 1831 and gaining admission to the school. He was never31 below the first rank of scientists. He graduated with highest hon wide range of scientific interests, and a reputation for tenacity.

His first job was with the Ministry of Tobacco. He had decided^! career in chemistry, and his objective was to work with renowned cheat Joseph Louis Gay-Lussac. Le Verrier fell so in love with Paris and his f^ wife that he left government service two years later rather than act* the usual tour of duty in the provinces. He spent a year teaching* then rejoined Gay-Lussac when his mentor was appointed to the Éc^ Polytechnique faculty and created an assistant's position for him.

Le Verrier's first published papers were in chemistry. Gay-Lussac Sk talent there, but even greater skills in mathematics. When a profess» ship in astronomy opened at the École Polytechnique in 1837, he arraiçj for Le Verrier to be appointed and encouraged his colleague, now 26^ old, to switch fields. Le Verrier did, studying astronomy with li characteristic ferocity and applying his mathematical incisivenesj'lor. He worked extremely hard so that his initial publications in astronoo| would be worthy of his distinguished predecessor Félix Savary, of lj mentor Gay-Lussac, and of his own high standards. Le Verrier's first h» papers showed extraordinary analytical powers, and he was befriends (as most promising young scientists were) by Arago in 1840.

Arago gave him the problem of the motion of the planet Mercury, whxs was always ahead of where its calculated orbit predicted it would k Le Verrier worked on the problem for three years and explained mos of the variance as perturbations caused by other planets. But he was lé with a small discrepancy that he could not explain

With the Mercury problem initially intractable, Le Verrier turned hi attention to cometary orbits with great success. In June 1845, Aragoap proached him again—this time with the most difficult and intriguii. puzzle facing contemporary astronomers: the motion of Uranus. LeVte-rier was now 34, eight years older than Adams. He was already inter» tionally known for his mathematical analysis of astronomical problems

Le Verrier began with an exhaustive analysis of the motion of Urania as presented in Bouvard's Tables. On November 10, 1845, Le Veme: presented to the Paris Academy of Sciences the first of three papers« Uranus. It dealt exclusively with old and modern observations«* demonstrated that they were irreconcilable—there really was a problea with -.he planet's motion, not with the quality of the observations.'.?

he announced, analyze those outside causes in a second paper W°u ____nut that Bouvard was wrone in ienorine the nosi-

of Uranus observed prior to its recognition as a planet.

ti0nS vim/ember 10, 1845, while Le Verrier was giving his preliminary On No\ ...»____i___i___________11_?__.______i . i »j.

He also pointed out that Bouvard was wrong in ignoring the positions i

^ rt'on the project that Arago had encouraged him to undertake, Adams '^receiving his astronomer royal's most discouraging response to his Wtculation of where a new planet could be found.

. .t intentional or careless, was compounded a few weeks later i! Airv visited Challis at Cambridge University. Neither Challis nor W- invited Adams to meet Airy at last and discuss his work with him.

Meanwhile, in France, Le Verrier was hard at work preparing his sec-. er on Uranus. He presented it to the Paris Academy of Sciences lune 1 1846- This paper demonstrated that the irregularities in the motion of Uranus could be induced only by an unknown planet farther from the Sun. What had been suspected now had a solid mathematical basis that had been announced to a wide scientific community.

I* Verrier then went on to calculate the planet's position, ending with the hope that "we will succeed in sighting the planet whose position 1 have just given."'2 The academy praised this new analysis, but to Le Verrier's amazement, no one offered or even suggested that a search should be undertaken.

Airy received a copy of Le Verrier's second paper on June 23 or 24, 1846. He immediately noticed that Le Verrier's prediction agreed to within one degree of Adams'. "To this time," wrote Airy, "I had considered that there was still room for doubt of the accuracy of Mr. Adams's investigations . . . But now I felt no doubt of the accuracy of both calculations .. ,"'3

Airy responded immediately with a letter to Le Verrier expressing enthusiasm and delight. Le Verrier was eight years older than Adams and an established scientist. He was worthy of notice. Airy's response was also in character, wrongheaded and neglectful. Had Le Verrier considered the possible need to modify the length of the Uranus radius vector (the Sun-to-Uranus distance ? It was the same inane question he had asked Adams. But Airy didn't bother to mention that Le Verrier's fine work had been matched eight months earlier by a young mathematician at Cambridge. And, of course, Airy did not bother to share his "delight and satisfaction" with Adams.

Airy must have been even more impressed than his reply to Le Verrier .. R

indicated, because three days later, when the Board of Visitors (the com- ^ Begins mission that conducted periodic inspections) of the Royal Observatory Move convened at Greenwich on June 29, Airy proclaimed "the extreme prob-

ability of now discovering a new planet in a very short time .. ." jj confident because Adams' and Le Verrier's calculations of the po^K of the planet disturbing Uranus coincided so closely. Still Airy mark effort to notify Adams, nor did he bother to authorize a search. SajB on this board, hearing these words, were James Challis and l!? Herschel.14

Upon hearing this news, Challis behaved inexplicably. Instead of (am. recognizing the opportunity that had been staring him in the facefj year, instead of starting a search on his own, Challis now lost whate^ little interest he had in the matter and what little confidence he had1 Adams' predictions. Perhaps he thought that Airy had preempted tfe project.

Le Verrier received Airy's reply on June 28. Since he had dealt win Airy only a few times previously, he was impatient rather than d» couraged. He immediately informed Airy in firm icy tones that the» tronomer royal's question was irrelevant because his calculations deal with perturbations on Uranus and where they were coming from, bent, the exact distance of Uranus from the Sun was corrected for auto matically." Having dismissed the astronomer royal's objection, Le%. rier went on to offer to send specially calculated position predictionstc simplify the quest for the new planet if Airy had "enough confide«* in my work to search for the planet in the sky ..." Airy received the offer on July 1 and again responded immediately. He declined Le Voder's offer because, he said, he was about to leave for business on tie continent. His trip was actually scheduled for August 10, five and a half weeks away.

The next day Airy again visited Cambridge University. He was ¡nth* company of visiting astronomer Peter Andreas Hansen, director of the Seeberg Observatory near Gotha, Germany (which Zach had helped to build and had directed). Despite Le Verrier's recent letter and despite his own statement to his observatory's Board of Visitors that the irregular motion of Uranus would soon lead to the discovery of a new planet, the astronomer royal made no effort to contact or meet with Adams. II happened anyway, but accidentally. That evening Airy and Hansen en countered Adams on St. John's Bridge. Airy introduced Adams to Hansen but was very cool and made no mention of Adams' calculations for! new planet. He cut off the conversation after about two minutes moved on.

A few days later, on July 6, Airy spent some time at Ely with Georgt Peacock, his old professor at Cambridge, and the subject of Uranus was broached. Airy told his mentor about his correspondence. Peacock was dumbfounded by his former student's negligence and urged him to act lly got the message, and three days later, on July 9, he wrote Airy f'"® * tQ request an urgent search. Presuming Challis' answer James native, because such a project would likely be time-consuming wouldlbe ^ 0ffered an assistant from the Royal Observatory to help, andtefli . jaid Airy, was "almost desperate," neglecting to acknowl-The That he had delayed a search for nine months, ^ur dayS later, without waiting for Challis to reply, Airy wrote again, f'01^ sending him a complete set of instructions for the search, v." except emergency unpostponable observations should be allowed ^"intervene said Airy, because "the importance of this inquiry exceeds that of any current work..."

Challis was away from Cambridge when the letters arrived. When he returned he was of course offended by Airy's imperious and condescend-manner. In his reply o: July 18, Challis told Airy that he had already derided to look for the planet himself and therefore declined an assistant.

It made sense for the Cambridge Observatory, rather than the Greenwich Observatory, to conduct the sear ch. Greenwich primarily had transit telescopes, which could pivot up and down but not side to side. They were locked into position along the meridian so that they could observe exactly when a star, planet, the Moon, or the Sun crossed the north-south line for purposes of calculating time, longitude, and orbits. The Cambridge Observatory had the 11.75-inch (30-centimeter) Northumberland Telescope, equatorially mounted so that it could be aimed at any point in the sky and with more than enough light-gathering power for this kind of search.

But for the next week and a half Challis did nothing. Then, late in July, Challis BeainS

Challis told Adams of the projected search. Adams provided updated posi-

tion predictions for the planet and gave Challis very encouraging news:

The planet should be large enough to show a disk. Thus a careful observer would be able to recognize the new planet as other than a star without having to wait a day or so to see if the suspected object moved among the background stars.

On July 29, 1846, Challis began his search, resigned to the prospect of a long, tedious, and fruitless task because mathematics was no way to find a planet. Placing no confidence in the quality of Adams' or Le Verrier's calculations and ignoring Adams' advice that the planet should show a disk, Challis agreed with Airy that it was useless to concentrate on the positions that Adams and Le Verrier had predicted. Instead he prepared to search a swath of sky 30 degrees long and 10 degrees wide— 15 degrees to the east and west and 5 degrees to the north and south

Final Predictions of the predictions. Challis' plan was to sweep this region steadily, rec^ ing all but the dimmest stars, and then to return to that region a fewdat later to reexamine each star to see if one had moved. Such a search woidj require mapping at least 3,000 stars and would consume at least 300 hou, of telescope time—approximately eight straight weeks of good observ ing weather. This was the only way, unless he was to value the \VOrj of Adams and Le Verrier and concentrate his search on the region of tin sky where they predicted the planet would be. If he had, his efforts wouli have succeeded within a few nights.

On August 12, 1846, two weeks into his search, but on only his fou^ night of acceptable observing conditions, Challis and his assistants^ corded in his notebook the new planet almost exactly where it wj, predicted. But Challis failed to recognize his target.

Le Verrier's second paper, identifying an outlying planet as the souict of Uranus' peculiar motion and predicting its position, circulated wide. ly. Sears Cook Walker, a young astronomer at the United States Naval Observatory in Washington, D.C., read of Le Verrier's work and proposed to search. But Matthew Fontaine Maury, superintendent of the observatory, rejected the proposal because of his facility's heavy schedule.

Le Verrier kept pushing forward. On August 31, 1846, he presented bis third and final paper on Uranus to the Paris Academy of Sciences, tt|is time laying out the orbital elements, the mass, and the position of the planet that was disturbing Uranus. His refined positional calculation differed only slightly from his previous prediction. The planet, he said, was about 5 degrees east of Delta Capricorni. To encourage a search, Le Verrier stressed that the planet was just past opposition—closest to Earth and visible almost all night long. The planet was big enough to showa disk, so that a long, tedious mapping of stars would not be necessary. He received polite applause from his scientific audience and, once again, not a single offer to search for the planet from any astronomer, not even his champion Arago.

Adams did not know of Le Verrier's third paper when, on September 2, he sent Airy his sixth solution to the problem, refining a little bit further his prediction of where the disturbing planet would be found. This calculation explicitly included a correction for the distance of Uranus from the Sun, the matter about which Airy had previously expressed concern. Airy was now actually away on his trip to the continent, and Adams received a mindless reply from Robert Main, Airy's chief assistant, offering more observational data on Uranus.

Adams now at last resolved to lay his work before the scientific com-

He decided to present his findings at a meeting of the British mUr"t' tion for the Advancement of Science in Southampton in mid teniber But when he arrived on September 15, he found that there \!a hppn a confusion in the conference announcement. The astronomy ■ had already concluded, and there was no other appropriate forum r^him The irony was overwhelming when Adams heard that John u «:hel had opened the conference with his valedictory address as president of the association by heralding the prospect of a new planet: "Its movements have been felt. . . with a certainty hardly inferior to that of ocular demonstration."15

In France, Le Verrier was also frustrated. His countrymen praised his mathematical virtuosity, but no one was willing to invest time in a search for the planet. Airy in England had declined to search, as far as he knew. Then Le Verrier remembered a doctoral dissertation he had received from lohann Gottfried Galle, an assistant at the Berlin Observatory. Almost a year had passed and Le Verrier had failed to acknowledge the gift. On September 18, 1846, Le Verrier picked up his pen, praised the young astronomer, and enclosed his position predictions for the new planet with the request that Galle attempt a search.

Johann Galle

The letter reached Galle on September 23, 1846. He rushed into the office of Johann Franz Encse, the director of the Berlin Observatory, to request permission to use the institution's fine 9-inch (23-centimeter) refracting telescope for the project. It took considerable pleading before Encke gave way. It was Encke's birthday and he intended to celebrate at home with his family, so he had no personal plans for the telescope that night.16 Heinrich d'Arrest, a young graduate student at the observatory, overheard the discussion in progress, boldly joined in, and begged to be allowed to help. "Let us oblige the gentlemen in Paris," said Encke finally, and departed.17

Galle and d'Arrest could scarcely wait for nightfall. They opened up the observatory dome and started looking for the new planet. As d'Arrest stood by, Galle searched the region around the position specified by Le Verrier—right ascension 21 hours 46 minutes, declination -13 degrees 24 minutes—in hopes of identifying the planet by its disk. But the planet was not immediately evident in the field of view and in surrounding fields.

Then d'Arrest suggested that they use a star map and compare stars in the sky with those on the chart to find one that wasn't plotted. Galle was reluctant. The star maps he had been using (such as those by Carl Ludwig Harding) were nnt very reliable. Nevertheless, there seemed to be no other choice.

Berlin

Johann Encke. director of the Berlin Observatory

The Berlin Observatory as it was about the time that Neptune was discovered

The Berlin Observatory as it was about the time that Neptune was discovered

Galle and dArrest hunted through the map files. There, to their delight they found an excellent new chart of the region in Aquarius that they needed. They had not known that this particular map existed. Prepared by Carl Bremiker, their own observatory's staff mathematician and map-maker, this chart was a product of the Berlin Observatory's involvement with other German observatories in a full-sky mapping project in augurated in 1830 at the urging of Friedrich Wilhelm Bessel to help with the search for more asteroids. (No new minor planets had been discovered since 1807.) Bremiker's chart of Hora XXI (right ascension hour 21 and one hour to either side) had been printed earlier that year but had not yet been released for distribution, possibly so that the Berlin Observatory could enjoy a temporary advantage.18

The two astronomers went back to work: Galle with his eye to the telescope, calling out each star in his field of view; d'Arrest off in a corner with a dim lamp shielded from Galle's eyes, matching each star as it was announced with one of the right position and brightness on the map "On the chart," he would respond. Galle would call another. 1

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