Uranus

Uranus' Moons

Overview

Uranus was the first planet to be discovered in modern history. It was actually discovered by accident in 1781 by William Herschel.

Like the other gas giants, Uranus has a very thick cloud cover and an atmosphere made up mostly of hydrogen, helium, methane, and ammonia. The trace amount of methane is what gives Uranus and its twin, Neptune, their blue color. Unlike Saturn and Jupiter, Uranus has a different internal structure.

The core of Uranus is probably composed of liquid rock. Then, farther up, the liquid rock slowly gives way to an ocean made mostly of hydrogen, helium, and water, with small amounts of ammonia and methane. This "ocean" accounts for most of Uranus's bulk. Then, the water slowly thins out into the bland, almost featureless atmosphere.

Uranus also has a system of about 11 rings - not nearly as large as Saturn's. Nine were found when Uranus passed in front of a bright star in 1977, for the rings causing the star to temporarily disappear when they passed in front of it. This was the first time astronomers had detected rings around any planet other than Saturn. It was the first time, also, that astronomers had detected thin rings around any planet. The other two rings were found when Voyager 2 passed by.

Uranus also has known moons, most of which little is known about.

Atmosphere

Uranus is basically one big atmosphere - as far as we know, there is no real surface to the planet. Its composition is nearly all H₂; the rest is approximately:

• H₂: 82.5±3.3%
• He: 15.2±3.3%
• CH₄: 2.3%
• HD: 0.0148%

Besides this, aerosols of ammonia ice, water ice, and ammonia hydrosulfide exist in the atmosphere. Methane ice may also be present.

The temperature at 1 bar is approximately 76 K, and at 0.1 bar it is 53 K. The density at 1 bar is 420 g/m³. Wind speeds range up to 200 m/s. The scale height of the Uranian atmosphere is about 27.7 km.

Unique Characteristics

Uranus has two main unique features:

• First, there is absolutely no detail in the cloud cover. Only when pushed to the maximum level of color enhancement and contrast on computers do scientists start to see small swirls in the atmosphere.
• Second, Uranus is the only planet rotates on its side. This produces the strangest seasons of any planet in the solar system. For 21 years, Uranus's moons are seen as one would view a dart board, with one pole facing the sun. The next 21 years Uranus has its side to the sun, and the moons move up and down across the equator. then the cycle repeats itself starting with the other pole. Scientists aren't sure why this is, but they think that a large body smashed into it with such force that it pushed the planet over.

Satellites that Have Visited

1. Voyager 2 - 1 flyby in 1986

Mythology

Uranus was named for the ancient Greek god of the heavens. When Earth was first made, Uranus was the first thing she saw, and they fell in love.

Data for the Rings

Data for the Planets