175 years ago Johann Gottfried Galle received a letter from the French mathematician Urbain Leverrier at the royal Berlin observatory: “I am looking for a persistent observer who would be willing to spend some time studying a section of the sky in which there may be a planet to be discovered.” Leverrier had noticed that the planet Uranus, discovered some 60 years earlier, was not moving exactly as expected. Apparently the gravitational pull of another planet, unknown up to that point, disturbed its course. The extremely talented young mathematician then calculated the presumed position and asked his Berlin colleague to check the sky – because in Paris his work had not been taken very seriously.
Johann Gottfried Galle (1812-1910) discovered the planet Neptune on September 23, 1846 – thanks to the position of Urbain Leverrier (Romansky / AIP)
On the same evening, Johann Gottfried Galle, “Observator” – that was the name given at the time – at the observatory, set the telescope to the specified location and discovered the bald cave Neptune in the maze of stars. The following night the object had moved a little, an unmistakable sign of a planet. “The planet whose coordinates you have actually existed,” Galle reported to Lever. The Berlin astronomer was the first to discover the gilded Neptune or “calculator”.
The Berlin observatory at Hallescher Tor was demolished in 1913. But the telescope that was used to observe Neptune for the first time still exists: It is in the Deutsches Museum in Munich.