23 September

1846: On 23 September 1846, Neptune was first observed very near to the locations independently predicted by astronomers Adams and Le Verrier. They had made their calculations based on the positions of Jupiter, Saturn and Uranus.

An international dispute arose between the English and French (though not, apparently between Adams and Le Verrier personally) over priority and the right to name the new planet; they are now jointly credited with Neptune's discovery. Subsequent observations have shown that the orbits calculated by Adams and Le Verrier diverge from Neptune's actual orbit fairly quickly. Had the search for the planet taken place a few years earlier or later it would not have been found anywhere near the predicted location.