When was Neptune discovered?

Astronomers noticed that Uranus was not following its predicted orbit, suggesting an unseen planet was tugging on it. French mathematician Urbain Le Verrier calculated where the mystery planet should be and sent his prediction to Johann Galle in Berlin. Galle and his assistant Heinrich d'Arrest found Neptune on their first night of searching, within about one degree of the predicted position. English mathematician John Couch Adams had made similar calculations independently. Neptune was the first planet found by mathematical prediction rather than regular sky-searching.