Uranus is about four times the diameter of Earth and is the third largest planet. It orbits the Sun at a distance of approximately 1.8 billion miles. Uranus has 27 known moons, including its five largest - Miranda, Ariel, Umbriel, Titania, and Oberon. Uranus has a system of rings composed of ice particles. Although larger than Earth, Uranus' surface gravity is less due to its gaseous composition, which also gives it a blue appearance when viewed from Earth. Voyager 2 took almost nine and a half years to reach Uranus during its journey through the solar system.