The Far Planets - Uranus

Uranus is the seventh planet from the Sun, with the third largest diameter in the solar system. It was named for the father of the god Saturn in Roman mythology.

Uranus looks featureless through even the most powerful telescopes. Scientists believe the planet is shrouded in clouds that hide it from view. The presence of methane in the upper atmosphere is believed to account for the planet's light blue-green color. It takes eighty-four Earth years for Uranus to orbit around the TABLE 8.1 The rings of Saturn Linda J. Spilker, editor, "The Rings of Saturn," in Passage to a Ringed World: The Cassini-Huygens Mission to Saturn and Titan, National Aeronautics and Space Administration, Jet Propulsion Laboratory, California Institute of Technology, October 1997, http://saturn.jpl.nasa.gov/multimedia/products/pdfs/ptarw.pdf (accessed December 28, 2005)Sun. Uranus is unique in the solar system, because its axis is tilted so far from its orbital plane. The planet lies on its "side" as it orbits with a pole pointed toward the Sun.

TABLE 8.1
The rings of Saturn
Ring	Distance, Kilometers*	Width, kilometers
*Distance from Saturn to closest edge of ring.
SOURCE: Linda J. Spilker, editor, "The Rings of Saturn," in Passage to a Ringed World: The Cassini-Huygens Mission to Saturn and Titan, National Aeronautics and Space Administration, Jet Propulsion Laboratory, California Institute of Technology, October 1997, http://saturn.jpl.nasa.gov/multimedia/products/pdfs/ptarw.pdf (accessed December 28, 2005)
D	66,970	7,500
C	74,500	17,500
B	92,000	25,400
A	122,170	14,610
F	140,180	50
G	170,180	8,000
E	180,000	300,000

As of 2006 Uranus had twenty-seven known satellites. They are named after characters from the plays of William Shakespeare (1564–1616) and from the poem The Rape of the Lock by Alexander Pope (1688–1744).

Herschel Discovers Uranus and Two of Its Moons

The astronomer Frederic William Herschel (1738–1822) was born in Germany, but lived and worked in Britain. He dropped his first name and was commonly known as William Herschel. On March 13, 1781, he was searching the sky with his telescope when he discovered Uranus. Herschel wanted to name the planet "Georgium Sidus" in honor of King George III of England. However, the name Uranus was selected from ancient mythology.

A few years later, in 1787, Herschel was the first to spot satellites around the planet. He discovered the two largest moons, named Titania and Oberon.

More Moons

During the mid-1800s two more moons were discovered around Uranus by the British astronomer William Lassell (1799–1880). It was another century before the next moon was found. During the 1980s and 1990s more than a dozen new moons were added to the list. In 2003 four additional moons were discovered by the Hubble Space Telescope and astronomers at the Mauna Kea observatory in Hawaii: Margaret, Ferdinand, Mab, and Cupid.