When was Neptune discovered?

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Clouds in Neptune's atmosphere — Neptune A photograph of clouds in Neptune's atmosphere, taken by Voyager 2 in August 1989. The view is from below the planet's equator, and north is up. The Great Dark Spot (center left) is 13,000 km (8,100 miles)—about the diameter of Earth—in its longer dimension. Accompanying it are bright, wispy clouds thought to comprise methane ice crystals. At higher southern latitudes lies a smaller, eye-shaped dark spot with a light core (bottom left). Just above that spot is a bright cloud dubbed Scooter. Each of these cloud features was seen to travel eastward but at a different rate, the Great Dark Spot moving the slowest.

Neptune was discovered on September 23, 1846, when German astronomer Johann Gottfried Galle and his assistant Heinrich Louis d’Arrest identified the planet at the Berlin Observatory.1

The discovery was the result of mathematical predictions made to account for irregularities in the orbit of Uranus. While the British mathematician John Couch Adams had performed earlier calculations, the French astronomer Urbain-Jean-Joseph Le Verrier independently conducted a similar study and communicated his results to Galle, leading directly to the planet's visual identification. Consequently, credit for the discovery is shared between Adams and Le Verrier, though Galle and d’Arrest were the first to observe it.1