If you’ve got really good eyesight and amazingly dark skies, you can see Uranus without a telescope. It’s only possible with the right conditions, and if you know exactly where to look. Since it’s possible to see Uranus with the unaided eye, it’s amazing that it went undiscovered for almost all of human history. Uranus was only discovered in March 1781 by Sir William Herschel.
Actually, that’s not entirely true. There were several observations of Uranus before that, but in every case, it was mistaken as a star since it moves so slowly in the sky. The first recorded sighting was in 1690 by John Flamsteed, who spotted it at least 6 times. He cataloged it as the star 34 Tauri. The French astronomer Pierre Lemonnier also observed Uranus between 1750 and 1769.
And so, on March 13, 1781, the British astronomer William Herschel was surveying the sky with his telescope, looking for binary stars. He noticed a fuzzy disk in his telescope, and suspected that it might be a comet. Over a few nights he realized that it was moving against the background stars, but it was moving two slowly to be a comet. After doing the calculations, Herschel realized that he was looking at a new planet, the farthest ever seen from the Sun.
Herschel’s original plan was to name this new planet after King George III of England. But in the end, British astronomers decided to name the new planet Uranus, after the father of Saturn in Roman mythology.
Here’s an article from the Hubble educational site about the discovery of Uranus, and here’s an article from the Smithsonian Museum.
We have recorded an episode of Astronomy Cast just about Uranus. You can access it here: Episode 62: Uranus.