Tuesday, June 9, 2009

June 9: Johann Gottfried Galle

Johann Gottfried Galle
June 9, 1812 – July 10, 1910

Johann Gottfried Galle was a German astronomer at the Berlin Observatory who, with the assistance of student Heinrich Louis d'Arrest, was the first person to view the planet Neptune, and know what he was looking at (September 23, 1846). He used the calculations of Urbain Le Verrier to know where to look.

Born in Radis, Galle studied at the University of Berlin from 1830-33. He had started to work as an assistant to Johann Franz Encke in 1835 immediately following the completion of the Berlin observatory. In 1851 he moved to Breslau (Wrocław) to become professor of astronomy and the director of the local observatory.

Throughout his career he studied comets, and in 1894 (with the help of his son Andreas Galle) he published a list with 414 comets. He himself had previously discovered three comets in the short span from December 2, 1839 to March 6, 1840.

Galle's Ph.D. thesis, finished in the year of 1845, was a reduction and critical discussion of Ole Rømer's observation of meridian transits of stars and planets on the days from October 20 to October 23, 1706. Around 1845 he sent a copy of his thesis to Urbain Le Verrier, but only received an answer a year later on September 18, 1846. It reached Galle on September 23 and in it Le Verrier asked him to look at a certain region of sky to find a predicted new planet, which would explain the perturbations of the planet Uranus. The same night, after Encke gave him the permission against his own judgment, an object fitting the description was found, and it was confirmed as being a planet over the next two evenings.

Two craters, one on the Moon and the "happy face" one on Mars, the asteroid 2097 Galle, and a ring of Neptune, have been named in his honor.

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