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URANUS
Uranus is the third "gas giant" planet of four in proximity to the Sun. Overall, Uranus is the seventh planet in our solar system, residing at an average distance of 1.8 billion miles from the Sun (twice as far as Saturn). Its rotation is fairly quick, at about 18 hours, enough to flatten the planet at its poles (a characteristic of all gas giants). It takes 84 years for Uranus to revolve around the Sun and the greenish-blue planet has 21 known satellites. Six of these satellite discoveries have been since 1997, the latest being in mid 1999.
Atmosphere and Weather: For many years, it was generally understood that Uranus was a bland planet. However, recent analysis from the Hubble Space Telescope shows Uranus to be a very weather dynamic planet, characterized by huge storms (covering half the United States in size) and the brightest cloud tops in the outer solar system. Clouds enshroud the planet with a latitudinal banding like Jupiter and Saturn, although much more faint. The average temperature of the clouds is -315 degrees F and ammonia and methane ice crystals make up the cloud composition. It has been recently found that wind speeds on Uranus range from 90 to 360 mph and the planet's average temperature is a frigid -353 degrees F. Findings from the Hubble Telescope reveal that clouds circle Uranus at over 300 mph. Shown at right, this near infrared picture taken by the Hubble Telescope reveals the bright cloud tops on the left side of the disk. Like the other gas giants, Uranus has an atmosphere composed of mostly hydrogen, followed by helium and a little methane.
What is very interesting about Uranus is that the planet has an enormous 98 degree tilt on its axis. Basically, it is laying on its side. This makes for extreme seasons and when the Sun rises at one of the poles, that pole will receive the direct sunlight for 42 years. Therefore seasonal variations are immense, in that as the dark side of the planet comes out of its 40 plus year slumber, the frozen atmosphere heats up dramatically causing violent storms. Curiously though, Uranus is still warmer at its equator than the poles, even though the poles receive the direct sunlight. It is not well understood why. In addition, unlike the other gas giants, Uranus does not radiate more heat than it receives. This suggests that the planet may have a cold interior, but this is also open for debate.
A side note: Uranus has a very narrow, complex ring system that appears to be fragile in that it wobbles. The other gas giants do not have "wobbly" rings. Technically, Uranus is the last planet in our solar system which can be seen by the naked eye. However one has to have an extremely dark sky and very good eye sight to spot Uranus without the aid of binoculars. Uranus shines at an average magnitude of +5.5 which is beginning to push the limits of what the human eye can detect. Looking in the proper location, Uranus can be easily found through a pair of standard binoculars.
Uranus appears blue, and is a gas giant, much like Jupiter, Saturn and Neptune.
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The Giant planets do not have the same layered structure that the earthlike planets do. Their evolution was quite different than that of the earthlike planets, and they have much more gas and ice inside.
Uranus's interior is primarily made of methane ice.
Motions in the interior of Uranus help form the magnetosphere of Uranus. Heat generated within Uranus helps form the unusual winds of the atmosphere.
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The plain aquamarine face of Uranus confirms the fact that Uranus is covered with clouds. The sameness of the planet's appearance shows that the planet's atmosphere is mostly composed of one thing, methane. The planet appears to be blue-green because the methane gas of the atmosphere traps red light and does not allow that color to escape. Beside clouds of methane crystals low in the atmosphere, smog, composed of ethane (the same product that can provide fuel for automobiles), is also present high in the atmosphere. The cloud particles constantly recycle themselves, first creating then destroying the heaviest crystals. This is an indication that Uranus' atmosphere is still evolving from its formation out of the solar nebula. Because Uranus lies on its side, Uranus has very strange seasons. Motions in the cloud patterns indicate that, like Jupiter and Saturn, the basic weather of Uranus can be described as a striped pattern of winds. This means that, even though the pattern is hard to see, Uranus is striped, just like Jupiter and Saturn.
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Planet
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Diameter: 51 118 km
Minimum Distance from Sun: 2735 million km
Maximum Distance from Sun: 3004 million km
Rotation Period around Axis: 17.23 hours
Revolution Period: 84.01 Earth years
Tilt of Axis: 97.9
Average Surface Temperature: -210
Number of Satellites: 15
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