Home > Encyclopedia of Science > Uranus

• Discovery of the planet
• Voyager 2 mission to Uranus
• Uranus's moons
• Uranus's rings

Uranus, the seventh planet from the Sun, was probably struck by a large object at some point in its history. The collision knocked the planet sideways, giving it a most unique orbit. Unlike the other planets, whose axes are generally upright on their orbits, Uranus rotates on its side with its axis in the plane of its orbit.

It takes the planet slightly more than 84 Earth years to complete one revolution around the Sun and almost 18 Earth hours to complete one rotation about its axis. Because Uranus's poles—and not its equator—face the Sun, each pole is in sunlight for 42 continuous Earth years.

Discovery of the planet

Uranus was...