Johann Gottfried Galle

Johann Gottfried Galle (1812–1910) was a German astronomer who observed Neptune in 1846 at the Berlin Observatory, following calculations by Urbain Le Verrier.

Neptune: The eighth planet from the Sun, discovered in 1846 after its position was predicted mathematically. Galle observed Neptune near the position Le Verrier had calculated.
Celestial mechanics: The branch of astronomy that applies physical laws to the motion of celestial bodies. Le Verrier used celestial mechanics to infer a planet disturbing Uranus’s orbit.
Johann Franz Encke: A German astronomer who directed the Berlin Observatory during much of Galle’s career. Encke’s institutional leadership shaped Galle’s work at the observatory.
Scientific priority: The recognition of who first made a scientific discovery or established a result. Neptune’s discovery divided credit among Le Verrier, Adams, and the observers.
Urbain Le Verrier: A French mathematician whose calculations predicted Neptune’s position before its discovery. Galle used Le Verrier’s prediction to guide the search at Berlin.
Perturbation theory: A set of mathematical methods for estimating how small influences alter a system’s behavior. Gravitational perturbations of Uranus were the clues used to predict Neptune.
Friedrich Wilhelm Bessel: A German astronomer and mathematician known for precise stellar measurements and astronomical methods. Bessel’s precision-centered astronomy formed part of the German tradition Galle worked within.
Mathematical astronomy: The use of mathematical analysis to describe and predict celestial positions and motions. Neptune became a celebrated case of mathematical analysis guiding observation.
Berlin Observatory: A historic astronomical observatory in Berlin, founded in 1700. Galle and Heinrich d’Arrest searched for Neptune there in September 1846.
Planetary orbit: The path a planet follows around a star under gravitational influence. Comparing Uranus’s predicted and observed orbit exposed the unexplained deviations.

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