A life of research
Educated at the École polytechnique, he began in chemistry before turning to celestial mechanics. Much of his career was associated with the Paris Observatory.
He sought improved theories and tables of planetary motion. Small differences between predictions and observations became physical clues rather than inconvenient errors to ignore.
Understanding the contribution
He attributed some anomalies in Uranus’s motion to the pull of a more distant planet. On 23 September 1846 Johann Galle and Heinrich d’Arrest found Neptune in Berlin, guided by his calculations.
John Couch Adams had independently studied the same problem. Later, Mercury’s anomaly resisted explanation by an extra planet and found its solution in general relativity.