Uranus

Uranus is the seventh planet from the Sun and the third largest after Jupiter and Saturn. Uranus is a unique planet, as it orbits the Sun on its side instead of tilted by an angle 23.5° or more like the other planets. This has a big effect on the planet's seasons and weather patterns. No wonder when Voyager 2 flew past the planet it discovered that the planet is a blue-green ball of hydrogen and helium with no cloud features like the other worlds. In 1997, the Uranian spring emerged and scientists discovered a large group of cloud features and even a darker storm called the Uranus Dark Spot. Uranus also has the coldest planetary atmosphere with a temperature of -225°C and a cold core of 4725°C, much colder than the other gas giant cores. Uranus is dominated by a thick atmosphere of hydrogen, helium and ices such as ammonia and methane, an icy mantle and a small core of rock. Its core is hot, with a temperature of 4725°C (5000 K), but colder than the other gas giant cores. The temperature creates really slow convection. Uranus and Neptune do not have a liquid surface like the other giant planets, instead their mantle is the surface. This gives the planets the nickname Ice Giants.

Atmosphere and climate
The Uranian atmosphere is the coldest atmosphere of any planet in the Solar System. It is divided into layers like Earth's. The troposphere is the lowest and densest layer of the atmosphere, with a rising temperature of 53 K (-220°C) and an increasing pressure of 50 to 100 bar. People believe water clouds are present within this layer. The next layer is the stratosphere in which temperatures increase from 53 K to between 800 to 850 K (525 to 575°C). The high temperatures are caused by ultraviolet radiation getting absorbed by methane and ammonia.

Climate
Uranus probably has a highly seasonal climate, because it was inactive during Voyager 2's 1986 flyby. Eleven years later, the planet

Ring system
Uranus is surrounded by a number of rings, too faint to be seen from any telescope on Earth. The rings are composed of dark methane crystals, not ice crystals like Saturns. Thirteen rings are now known, with the brightest being the ε ring.

Moons
Uranus has 27 satellites. The moons are named after major characters from William Shakespeare's plays. The five largest are Miranda, Ariel, Umbriel, Titania and Oberon, the largest being Titania with a diameter of 1,578 km (980.5 miles). Titania is named after the Queen of the Fairies from Shakespeare's A Midsummer Night's Dream.

Missions

 * Voyager 2 - Voyager 2 flew by the planet in 1986 and is the only spacecraft (now) to visit it. It flew 81,500 km above the planet's cloudtops, studied its unique weather and seasons, caused by its strange axial tilt.

Planned mission

 * Uranus Orbiter and Probe - A planned mission by NASA scheduled to be launched during 2020-23 and will require a 13-year cruise to Uranus.