Discovery of Neptune - Aftermath

Aftermath

On the announcement of the discovery, Herschel, Challis and Richard Sheepshanks, foreign secretary of the Royal Astronomical Society, announced that Adams had already calculated the planet's characteristics and position. Airy, at length, published an account of the circumstances, and Adams's memoir was printed as an appendix to the Nautical Almanac. However, it appears that the version published by Airy had been edited by the omission of a "crucial phrase" to disguise the fact that Adams had quoted only mean longitude and not the orbital elements.

A keen controversy arose in France and England as to the merits of the two astronomers. There was much criticism of Airy in England. Adams was a diffident young man who was naturally reluctant to publish a result that would establish or ruin his career. Airy and Challis were criticised, particularly by James Glaisher, as failing to exercise their proper role as mentors of a young talent. Challis was contrite but Airy defended his own behaviour, claiming that the search for a planet was not the role of the Greenwich Observatory. On the whole, Airy has been defended by his biographers. In France the claims made for an unknown Englishman were resented as detracting from the credit due to Le Verrier's achievement.

The Royal Society awarded Le Verrier the Copley medal in 1846 for his achievement, without mention of Adams, but Adams's academic reputation at Cambridge, and in society, was assured. As the facts became known, some British astronomers pushed the view that the two astronomers had independently solved the problem of Uranus, and ascribed equal importance to each. But Adams himself publicly acknowledged Le Verrier's priority and credit (not forgetting to mention the role of Galle) in the paper that he gave to the Royal Astronomical Society in November 1846:

I mention these dates merely to show that my results were arrived at independently, and previously to the publication of those of M. Le Verrier, and not with the intention of interfering with his just claims to the honours of the discovery ; for there is no doubt that his researches were first published to the world, and led to the actual discovery of the planet by Dr. Galle, so that the facts stated above cannot detract, in the slightest degree, from the credit due to M. Le Verrier.

The criticism was soon afterwards made, that both Adams and Le Verrier had been over-optimistic in the precision they claimed for their calculations, and both had greatly overestimated the planet's distance from the sun. Further, it was suggested that they both succeeded in getting the longitude almost right only because of a "fluke of orbital timing". This criticism was discussed in detail by Danjon (1946) who illustrated with a diagram and discussion that while hypothetical orbits calculated by both LeVerrier and Adams for the new planet were indeed of very different size on the whole from that of the real Neptune (and actually similar to each other), they were both much closer to the real Neptune over that crucial segment of orbit covering the interval of years for which the observations and calculations were made, than they were for the rest of the calculated orbits. So the fact that both the calculators used a much larger orbital major axis than the reality was shown to be not so important, and not the most relevant parameter.

The new planet, at first called "Le Verrier" by François Arago, received by consensus the neutral name of Neptune. Its mathematical prediction was a great intellectual feat, but it showed also that Newton's law of gravitation, which Airy had almost called in question, prevailed even at the limits of the solar system.

Adams held no bitterness towards Challis or Airy and acknowledged his own failure to convince the astronomical world:

I could not expect however that practical astronomers, who were already fully occupied with important labours, would feel as much confidence in the results of my investigations, as I myself did.

By contrast, Le Verrier was arrogant and assertive, enabling the British scientific establishment to close ranks behind Adams while the French, in general, found little sympathy with Le Verrier. In 1874–1876, Adams was president of the Royal Astronomical Society when it fell to him to present the gold medal of the year to Le Verrier.