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Uranus Explained

        Science | The Solar System

This Hubble Space Telescope picture of Uranus was taken in infrared light so that scientists could get more information about the layers of Uranus's atmosphere. The different colors of the planet show different layers, and the reddish fringe around the edge shows a very thin haze that surrounds the planet.
This Hubble Space Telescope picture of Uranus was taken in infrared light so that scientists could get more information about the layers of Uranus's atmosphere. The different colors of the planet show different layers, and the reddish fringe around the edge shows a very thin haze that surrounds the planet.
Photo courtesy of NASA

Uranus is the seventh planet from the sun, and is named for the ancient Greek deity of the Heavens, the earliest supreme god. It is the third largest planet in the solar system, and is three times as large as Earth.

Uranus's atmosphere is rich in hydrogen and helium. If you look at Uranus through a telescope, you will see that it is a brilliant blue-green color, which is caused by the methane gas (about 2 percent) that is also present in its atmosphere. Images from the spacecraft Voyager show Uranus as a colorful blue world with absolutely nothing happening. But first impressions can be deceiving. Although this giant gas planet may look bland, the winds on Uranus whip around the planet at speeds of hundreds of miles an hour. As it turns out, this planet is anything but bland.

Curiously, the equator (the "waist") of this strange world is almost at right angles to the planet's orbit around the sun. So Uranus rotates from south to north rather than east to west (or west to east as with Venus) as Earth and all the other planets do. It is possible that the planet was tilted on its side billions of years ago when it was hit by an object large enough to change the way the planet rotated. Because of this unusual tilt, Uranus has very extreme seasons. It takes Uranus 84 Earth years to travel around the sun. In fact, it's so far away from the sun that it's temperature is somewhere close to -200° C. The length of a day on Uranus is 17 hours and 24 minutes.

Like Saturn (and the rest of the gas planets), Uranus also has a ring system. The rings are very, very faint and can only be seen by instruments such as the Hubble Space Telescope or visiting spacecraft such as Voyager. The rings are made up of large ice boulders (several feet across) and space dust.

Voyager sent back this interesting image of a part of Uranus's rings. Scientists study images like this to learn more about the planet's rings.
Voyager sent back this interesting image of a part of Uranus's rings. Scientists study images like this to learn more about the planet's rings.
Photo courtesy of NASA

Uranus has a very interesting family of moons. It has at least 27 moons. They are a wide variety of rocky moons, icy moons, and some that are a combination of both. One of the most puzzling of Uranus's moons is tiny Miranda. Although that moon is only about 300 miles in diameter, the Voyager mission sent back a picture showing a cliff that is more than ten miles high. Earth's highest mountain, Mount Everest, is only about five and a half miles high. Images of Miranda show that it has lived a very tough life, shown by the many fractures on its surface.

Uranus had been seen for many years, but everyone who saw it thought it was a star, not a planet. In 1781, Sir William Herschel became the first person to identify Uranus as a planet. He also discovered two of its moons. In 1782, King George III of England (of U.S. Revolutionary War fame) named Herschel the King's Astronomer.