January 21: John Couch Adams

John Couch Adams 

June 5, 1819 – January 21, 1892

John Couch Adams was a British mathematician and astronomer. His most famous achievement was predicting the existence and position of Neptune, using only mathematics. The calculations were made to explain discrepancies with Uranus's orbit and the laws of Kepler and Newton. At the same time, but unknown to each other, the same calculations were made by Urbain Le Verrier. Le Verrier would assist Galle in locating the planet on September 23, 1846, which was found within 1° of its predicted location, a point in Aquarius. There was, and to some extent still is, some controversy over the apportionment of credit for the discovery.

Although he was not an active lunar observer, he was (as Wilkins and Moore point out) an outstanding mathematician and greatly improved the "lunar theory" (i.e., our understanding of the Moon's orbit).

The Lunar crater Adams is jointly named after him, Walter Sydney Adams and Charles Hitchcock Adams. Neptune's outermost known ring and the asteroid 1996 Adams are also named after him. The Adams Prize, presented by the University of Cambridge, commemorates his prediction of the position of Neptune. His personal library is now in the care of Cambridge University Library.