Uranus may have been struck by a planet-sized object early in its life and knocked onto its side. Consequently, Uranus's axis is tilted 98 degrees compared with the Earth's 23.5 degrees.
Like the other gas giant planets, Uranus has no solid surface. It gets its bluish surface colour from tiny frozen ammonia crystals. The atmosphere is thought to be mainly hydrogen and helium.
Uranus has only been visited once, by the Voyager 2 probe.
Photo: Uranus taken by the Voyager 2 probe (NASA)
The seventh planet from the Sun orbits on its side.
The distant icy objects may help explain Uranus and Neptune's formation.
Scientists studying how the Solar System formed are interested in the Kuiper Belt, a region of icy objects beyond Neptune. It is thought that the Kuiper Belt objects may explain the formation of the outer planets Uranus and Neptune.
Enjoy Astronomer Marek Kukula's guide to the Solar System.
If Jupiter were much larger it would be a star in its own right! Enjoy Astronomer Marek Kukula's eloquent guide to the Sun, the planets and the outer reaches of the Solar System.
Miranda lifts scientists' spirits after disappointment at Uranus.
Despite the careful work of engineers, Voyager 2 saw only impenetrable cloud at Uranus. Uranus's moon Miranda, with its fractured surface, proved more interesting to scientists. The Voyager probes were launched in 1977.
Learn how to remember all the planets of the Solar System in order.
Here’s an animated guide to remembering all the planets of the Solar System in order, using an easy mnemonic trick.
Uranus is the seventh planet from the Sun. It has the third-largest planetary radius and fourth-largest planetary mass in the Solar System. Uranus is similar in composition to Neptune, and both are of different chemical composition to the larger gas giants Jupiter and Saturn. Thus, astronomers sometimes place them in a separate category called "ice giants". Uranus's atmosphere, although similar to Jupiter's and Saturn's in its primary composition of hydrogen and helium, contains more "ices", such as water, ammonia, and methane, along with traces of hydrocarbons. It is the coldest planetary atmosphere in the Solar System, with a minimum temperature of 49 K (−224.2 °C), and has a complex, layered cloud structure, with water thought to make up the lowest clouds, and methane the uppermost layer of clouds. In contrast, the interior of Uranus is mainly composed of ices and rock.
It is the only planet whose name is derived from a figure from Greek mythology rather than Roman mythology like the other planets, from the Latinized version of the Greek god of the sky, Ouranos. Like the other giant planets, Uranus has a ring system, a magnetosphere, and numerous moons. The Uranian system has a unique configuration among those of the planets because its axis of rotation is tilted sideways, nearly into the plane of its revolution about the Sun. Its north and south poles therefore lie where most other planets have their equators. In 1986, images from Voyager 2 showed Uranus as a virtually featureless planet in visible light without the cloud bands or storms associated with the other giants. Terrestrial observers have seen signs of seasonal change and increased weather activity in recent years as Uranus approached its equinox. The wind speeds on Uranus can reach 250 meters per second (900 km/h, 560 mph).