Uranus is the seventh planet from the Sun and is about 14 times heavier than Earth. It was discovered in March 1781 by William Herschel.
Mass: 8.68 x 1025 kg
Composition: Ice and rock
Orbit: 3,000,000,000 km from the Sun
Distance from other planets: View matrix
Uranus was the first planet to be discovered using a telescope from Earth. There are 27 known moons orbiting Uranus. The five largest moons were also observed through telescopes on Earth, while the other smaller moons were found later by various spacecraft missions. Uranus also has two sets of rings made of tiny dust particles. Discovered in 1977, the first set consists of nine rings which are dark grey in colour and are narrow. Two brightly coloured rings, one blue and one red, were also found by astronomers further away from Uranus after they studies images from the Hubble Space Telescope. Because they are so far away from Uranus, they are known as the outer rings. There are now 13 known rings around Uranus, which also makes it only one of two planets in the Solar System with rings. The other planet is Saturn.
The man who first observed Uranus, William Herschel, was invited to name the new planet, but his desire to name it after King George III, the British monarch at the time, was rejected. The planet was subsequently named after the Greek god of the sky. All of Uranus’s moons are named after characters from the works of either William Shakespeare or Alexander Pope. The main moons are Ariel, Miranda, Oberon, Titania and Umbriel, with Titania being the largest. All of these satellites are composed of equal quantities of rock and ice.
Uranus has a core of rock and an icy mantle and the planet is surrounded by an outer atmosphere mainly consisting of hydrogen and helium. It glows with a blue-green colour, which is due to a certain amount of methane being present in the atmosphere. The planet has no distinctive geological features.
Uranus orbits the Sun from east to west once every 84 years. The planet is unusual, as its poles lie where the equators of most planets lie. It can therefore be calculated that each pole has 42 years of continuous sunlight immediately followed by a further 42 years in complete darkness. This unusual tilt has been attributed to a collision early on during the formation of the Solar System.
In 1986, the Voyager 2 spacecraft mission travelled past Uranus and observed that while the southern hemisphere was basking in sunlight, the northern hemisphere was in complete darkness The main purpose of the mission, however, was to explore the atmosphere and weather patterns. Data was also gathered about the five largest moons and Voyager 2 also discovered ten new moons during this time.