July 11

Neptune is the only planet discovered through mathematics. Urbain Le Verrier, a French astronomer, noticed irregularities in the motions of other planets and calculated that there must be an eighth planet lurking beyond Uranus based on these perturbations. On September 23, 1846, German astronomer Johann Galle of the Berlin Observatory used Le Verrier's calculations to discover the new planet. Neptune's orbit is roughly oval in shape, and it takes the planet about 165 years to complete one circuit. Neptune's first orbit since its discovery on September 23, 1846, was completed in 2011.
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