Uranus was first identified as a planet by William Herschel—a musician turned astronomer—in 1781. It had been observed before then, but had been labeled as a star—an easy mistake, since nobody had seen it move very far. At two billion kilometers (1.25 million miles) from the sun, Uranus takes 84.1 Earth years to complete one orbit!

Almost everything else we know about Uranus comes from the Voyager 2 mission, which visited Uranus in 1986—the only spacecraft from Earth ever to call on this planet.

Uranus is four times Earth's diameter and 14 times its mass.