On 12 July, Neptune will celebrate its very first birthday because exactly one Neptunian year -- or 164.79 Earth years -- will have passed since its discovery.
Neptune was mathematically predicted before it was first telescopically observed on 24 September 1846. Astronomer Johann Gottfried Galle and his assistant Heinrich Louis d'Arrest used Urbain Le Verrier's calculations to locate the planet. It was found to be within a single degree of where Le Verrier had predicted it would be and it was the first planet to have been discovered deliberately.
