Planet Uranus Facts

• Uranus is the seventh planet from the sun and the third largest in the solar system.
• Its diameter is 31,763 miles (51,118 km) which is four times larger than Earth.
• The planet is categorized as an ice giant due to the high levels of icy elements in its composition.
• Uranus is tilted on its side possibly after a collision with another planet.
• Its rather bland appearance has changed slightly since the Voyager 2 visit in 1985 as new cloud formations have appeared across the planet.
• Wind speeds in Uranus can reach 560 mph (900 km/h).
• Uranus is the farthest planet that can be seen without a telescope.
• Light from Uranus takes 2 hours 40 minutes to reach Earth.
• The interior of Uranus is made up of a dense hot liquid ocean comprising of water, ammonia and other volatile elements.
• Uranus was discovered in 1781 by the British astronomer William Herschel.

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Uranus orbits the sun every 84 years at an average distance of 1.8 billion miles (2.9 billion km) and spins on its own axis every 17 hours compared to 24 hours on Earth. Uranus has the coldest atmospheric temperature of any planet in the solar system, around -224C (-371F). Temperatures in its interior are lower than those found in the other outer planets, possibly less than 4500C (8132F) . The atmosphere of Uranus is made up of around 83% hydrogen, 15% helium, 2% methane and small amounts of ethane and other gases. The presence of methane gives Uranus its turquoise color. The rather featurless nature of Uranus's atmosphere is due to the lack of heat generated inside the planet.

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Uranus has 27 known satellites consisting of 5 large icy moons and a clutter of smaller moons. The largest of these is Titania (picture below) with a diameter of just under 1,000 miles (1600 km), around half the size of our own moon. Unusually instead of being named after Greek or Roman deities the satellites are named after characters from the plays of Shakespeare and the works of Alexander Pope.
William Herschel discovered Uranus in 1781 although he named the planet Georgium Sidus (George's Star) after the then King of England, George III. However the name was deeply unpopular outside of the United Kingdom so the German astronomer Johann Elert Bode named the planet Uranus after the Greek god of the sky. By the mid 19th century Georgium Sidus was no longer used and Uranus became the accepted name for the planet.

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Uranus and Neptune are categorized as ice giants rather than gas giants. Unlike Jupiter and Saturn they are not almost entirely composed of elements that are categorized as gases such as hydrogen and helium, instead Uranus and Neptune are made up mostly of elements that are categorized as ices such as water and methane.

Although there are slightly higher levels of icy elements in the atmospheres of Uranus and Neptune they are still primarily composed of hydrogen and helium like those of the gas giants. It is within the interiors of the planets that we start to see a large difference in composition.

The interiors of Jupiter and Saturn are composed of hydrogen, albeit in liquid or liquid metallic form due to extremely high pressure. The interiors of Uranus and Neptune are thought to contain very little hydrogen, instead they are mostly composed of water, ammonia and methane. This is where the term ices becomes rather confusing because the elements inside the ice giants are in no way cold, they are in fact extremely hot, forming a dense liquid ocean.

This has led scientists to come up with a rather intriguing and sparkly theory regarding the interiors of ice giants. Since methane is partly composed of carbon the high pressure could separate the carbon atoms from the methane and transform them into diamonds. It has even been speculated that deep within Uranus and Neptune diamond rain forms a liquid diamond ocean with iceberg sized diamonds floating on top.

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Diameter: 31,763 miles (51,118 km)
Average Distance from Sun: 1.8 billion miles (2.9 billion km)
Orbital Period: 84 years
Rotation Period: 17.24 hours

Maximum Temperatures: 7000C (12,600F) (Core)
Minimum Temperatures: -224C (-371F) (Cloud Tops)

Gravity: 8.43 m/s² (86% Earth's Gravity)
Density: 1.3 g/cm³ (23.6% Earth's Density)
Mass: 8.6849 x 10²⁵ kg (14 x Earth's Mass)
Volume: 6.8330 x 10¹³ km³ (63 x Earth's Volume)

Atmosphere: 83% Hydrogen, 15% Helium, 2% Methane.

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