Uranus

The first planet found with the aid of a telescope, Uranus was discovered in 1781 by astronomer William Herschel. The seventh planet from the Sun is so distant that it takes 84 years to complete one orbit.

Like Venus, Uranus rotates east to west. Uranus's rotation axis is titled almost parallel to its orbital plane, so Uranus appears to be rotating on its side. This situation may be the result of a collision with a planet-sized body early in the planet's history, which apparently radically changed Uranus's rotation. Because of Uranus's unusual orientation, the planet experiences extreme variations in sunlight during each 20-year-long season.