Photo courtesy of National Air and Space Museum

by Justine Leeco and Amy Irving

Uranus, the first planet discovered in modern times, was accidentally discovered in 1781 by the British astronomer, Sir William Hershel, but the planet was not called Uranus until 1850.

One of the giant gas planets in our Solar System, Uranus is a blue-green planet which can only be seen from the Earth with the naked eye on a dark, clear night. The seventh planet from the Sun, it is the farthest planet that you don't need a telescope to view it; The atmosphere of Uranus is made of 83% hydrogen, 15% helium, and 2% methane. The temperature in the atmosphere is so cold that the methane condenses and forms a thin cloud layer which gives the planet its blue-green color.

Uranus' axis is on a 98 degrees tilt because of the large, heavy space objects hitting it; when seen from Earth, it seems to rotate on its side. At different times throughout its orbit, one of Uranus' poles can be seen head on; Uranus is called the sideways planet. Uranus is 4 times bigger than Earth, and is nearly 3 billion km from Earth. The temperature there is -216 degrees Celsius, and the winds on Uranus blow 40 to 160 meters per second. Uranus's winds blow in the same direction as the planet rotates, to the east, just as on Earth. The winds can reach speeds up to 600 km per hour, because of the very fast rotation of Uranus' axis.

Uranus has a system of rings which are thin, dark and hard to see; they weren't discovered until spacecraft Voyager 2 visited the planet in 1977. Uranus' rings are different from those surrounding Saturn and Jupiter. The 11 rings of Uranus, made of different sized particles, form a 9400 km wide belt extending to 51,000 km from the planet's center. Naturally occurring satellites or moons found in the rings create gaps between the rings. In September, 1999, astronomers discovered 3 new moons for Uranus, making a total of 21 moons both within the rings and outside of the rings of Uranus; Uranus has the most moons of any planet in our Solar System.

One of Uranus' moons is Miranda. Miranda is the smallest moon; it is 500 km in diameter. Some astronomers believe that it was destroyed by a comet or asteroid and was put back together by gravity, because of its surface; it has canyons as deep as 20 km. The largest canyon is Puck; it's about 150 km larger than most asteroids. Miranda has a low temperature of -187 degrees Celsius, and is made of rock and ice. Titania, another of Uranus' moons has canyons marked by large faults. Ariel, another moon has craters greater than 50 km in diameter. Another moon, Umbriel, is ancient, has dark large craters, and has a coating of dust. Oberon is the farthest out of the pre-Voyager moons; it has an old heavily cratered surface with little evidence of movement. Oberon and Titania are the two largest moons of Uranus.

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