Today in History: Uranus

On this day (March 13) in 1872 Sir William Herschel discovered the planet Uranus—except he wasn’t actually the first person to sight it. In 128 BCE Hipparchos included Uranus in his star catalogue and Ptolemy incorporated it from Hipparchos’s work into his own Almagest. In 1690, John Flamsteed observed it six times cataloguing it as 34 Tauri. Pierre Charles Le Monnier observed it at least twelve times between 1750 and 1769. None of these people, however, realized they were looking at a planet. Even Sir William Herschel originally identified it as a comet. It was other astronomers who realized that Herschel’s comet was actually a planet.