On March 13, 1781, Sir William Herschel discovered Uranus, the seventh planet from the sun. Before Herschel discovered Uranus, other astronomers had seen it before, but no one realized it was planet. Instead, they thought it was a star. Herschel actually thought he was looking at a comet. Because it was moving, he figured it couldn't have been a star. Herschel and other astronomers spent two years debating about whether it was a comet or a planet. In 1783, Herschel finally announced that Uranus