Johann Gottfried Galle

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Lore & Background

Johann Gottfried Galle was a German astronomer, born in a house known as the Papsthaus, located west of Radis near Gräfenhainichen. He was the first son of a tar oven operator and his wife. Galle attended the Gymnasium in Wittenberg and later studied at Friedrich-Wilhelms-Universität Berlin. He began his career teaching mathematics and physics at a Gymnasium in Guben before transferring to a school in Berlin. In 1835, he became an assistant to Johann Franz Encke at the new Berlin Observatory, where he worked for sixteen years, primarily using a Fraunhofer refractor telescope. During his time there, he discovered an inner dark ring of Saturn and three new comets. He earned his doctorate with a thesis that reduced and critically discussed Ole Rømer's meridian transit observations. Galle is most famous for being the first person to view and identify the planet Neptune on 23 September 1846, following a prediction by Urbain Le Verrier. After receiving Le Verrier’s letter containing the predicted coordinates, Galle, with student Heinrich Louis d'Arrest, found an eighth-magnitude star within one degree of the calculated position that was absent from existing star charts. Subsequent observations of its proper motion confirmed it as a planet. Galle always credited Le Verrier as the discoverer. He later became director of the observatory in Breslau and a professor of astronomy there, working for over forty-five years. His research included determining planetary orbits, calculating aurora heights and meteor paths, and compiling data on comets. He also studied Earth's magnetic field and climatology, publishing over two hundred works. Galle died in Potsdam at age ninety-eight.

Reader's Guide

Johann Gottfried Galle’s career was defined by his work at the Berlin Observatory, where he served as an assistant to Johann Franz Encke for sixteen years, using a Fraunhofer refractor with an aperture of about 22.5 centimeters. In 1838, he identified an inner dark ring around Saturn, and between December 1839 and March 1840 he discovered three comets. His doctoral thesis, completed in 1845, involved a reduction and critical discussion of Ole Rømer’s observations of meridian transits of stars and planets from October 1706. Galle’s most famous achievement came on 23 September 1846, when he received a letter from Urbain Le Verrier containing coordinates for an undiscovered planet derived from perturbations in Uranus’s orbit. That same night, with student Heinrich Louis d’Arrest, Galle found an eighth-magnitude star not recorded on the Berliner Akademischen Sternkarte, just one degree from the predicted position. Over the next two nights, a proper motion of four arcseconds confirmed it as a planet, later named Neptune. Galle consistently refused credit for the discovery, insisting it belonged to Le Verrier. After leaving Berlin, he directed the observatory in Breslau for over forty-five years and became a professor of astronomy there, serving as rector for the 1875–76 academic year. He published more than two hundred works, focusing on precise planetary orbit calculations, methods for determining aurora heights and meteor paths, and a comprehensive catalog of all 414 comets known by 1894, compiled with his son. He also studied Earth’s magnetic field and climatology.

Did You Know?

• Galle always refused to be acknowledged as the discoverer of Neptune, attributing the discovery to Urbain Le Verrier.