Exploring the planet and its moons and rings.
Poor Uranus is the Rodney Dangerfield of the solar system. It doesn't get any respect and often finds itself as the butt of many jokes. (Literally.) But the seventh planet from the Sun is a beautiful and complex world.
Uranus is the first planet to have been "discovered." The other planets are easily spotted with the naked eye and have been observed by humans since the beginning of history. But Uranus, at magnitude 5.5, is extremely difficult to spot with the unaided eye and certainly never stood out to the ancients. It was William Herschel, in 1781, who first spotted Uranus and realized that it was more than just a star. How the universe must have seemed to expand to 18th century people upon learning of a new member of the solar system. Uranus was named for the Greek god of heaven and ruler of the world.
Uranus is the third largest planet and resides between Saturn and Neptune, at 19 AU from the Sun. Considering that Saturn is 9.5 AU from the Sun, Uranus is twice that distance. Because of its great distance, the only spacecraft to have visited this gas giant is Voyager 2.
As you can imagine, it takes Uranus a long time to make a circuit of the Sun just once. A Uranian year equals 84 Earth years. Uranus rotates once every 17 hours and 14 minutes, which makes its day shorter than an Earth day. But Uranus's rotation is more unusual than any of the other planets: It does not spin like a top, but appears to roll on its side like a ball. This is because, at sometime in the early years of the solar system, a planet-sized object struck Uranus and knocked it on its side.
Uranus receives feeble light from the Sun, and therefore is a frigid -350 degrees. Yet it still has a hot core, cooling since its formation about 4.6 billion years ago.
Uranus has approximately 11 rings and some partial rings. The rings are made up of black chunks of rock and ice that were unknown until Voyager 2's visit. The brightest ring is called epsilon.
At least 22 known moons orbit Uranus, and the five largest of them are named for Shakespearean characters. Titania is the largest moon with Oberon the second largest. The third largest, Umbriel, has a unique ring-shaped feature near the top nicknamed the "fluorescent cheerio". The fourth largest moon, Ariel, is the brightest, at magnitude 14. The fifth largest moon is also the strangest: Miranda. It has a curious mix of surface features. It is believed to be half water ice and half rocky, with deep grooves etched into its surface.
Viewing Uranus through binoculars or a telescope will reveal its blue-green hue. The clouds appear very uniform, however, new observing techniques are uncovering storms and other surprising structures in the atmosphere.
Although Uranus is a mysterious world that scientists know little about, there are no future missions currently planned for the planet.
For more on the solar system, follow the links below.
Sun Mercury Venus Earth Mars Jupiter Saturn Neptune
