Johann Galle 
In 1845, Johann Galle, a young astronomer at the Berlin Observatory, had sent a copy of his doctoral thesis to French astronomer Urbain Leverrier for comment. Galle didn’t get a reply for a year, but when he did, it included a request.
By calculating some oddities in the orbit of the planet Uranus, Leverrier had predicted that another planet was tugging at it. He told Galle where the planet should appear, and asked him to look for it. With permission of his boss, Galle did just that. And on the night of September 23rd, 1846, just a few days after receiving Leverrier’s note, he found it — the planet Neptune.
Galle was born 200 years today. While finding Neptune is his main claim to fame, he enjoyed a long and distinguished career. His main interest was comets, and he once discovered three of them in just a few weeks. He compiled one of the most extensive comet catalogs to date, listing more than 400 of them.
He also worked out a technique for measuring the scale of the solar system by measuring the angles to asteroids. It was a complicated idea, though, that couldn’t be pursued until well after Galle’s death.
Galle continued his research until the age of 83, and lived another 15 years after that.
To commemorate his work, Galle’s fellow astronomers have named an asteroid, craters on the Moon and Mars, and one of the rings of Neptune — the planet that Galle helped to discover — in his honor.
Tomorrow: the “milky” Milky Way.
Script by Damond Benningfield, Copyright 2012