Exploring The Planets: Uranus

This image of the planet Uranus was taken by the spacecraft Voyager 2 in 1986. Photo from: NASA/JPL-Caltech.

Uranus, the seventh planet from the sun, was the first planet to be discovered after the

invention of the telescope. It travels around the sun at an average distance of about 1.8 billion

miles.

Uranus was not known to ancient astronomers. At its brightest, the planet is just barely visible

to the unaided eye. It was seen in early telescopes several times but was thought to be just

another star. In 1781, as part of a telescopic survey of the stars, English astronomer William

Herschel discovered “a curious either nebulous star or perhaps a comet.” This unusual object

eventually proved to be a planet, the first to be identified in modern times. It was later named

Uranus, the personification of the heavens in ancient Greek mythology.

Physical Features

Uranus is the third largest planet in the solar system. Its diameter, or distance through its

center, is about 32,000 miles -- about four times the diameter of Earth. More than 60 Earths

would fit inside it! Uranus is most similar in size to Neptune, its outer neighbor.

By Encyclopaedia Britannica, adapted by Newsela staff on 08.31.17

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Uranus is one of four planets in our solar system that are known as gas giants. These planets

are made up mostly of gases. Uranus' composition is mainly hydrogen and helium. Like

Neptune, Uranus is blue-green in color, because of the small amount of methane in its

atmosphere, or surrounding layer of gases. Uranus has no solid surface. Underneath its huge

layers of gases, it has a smaller area of thick, hot liquid.

Narrow rings surround Uranus. Unlike the bright, icy rings of the planet Saturn, the rings that

surround Uranus are made of some unusually dark material.

More than 25 moons orbit Uranus. Its five major moons are Oberon, Titania, Ariel, Umbriel

and Miranda. They seem to be composed of ice and rock, and some of them have deep

valleys and many large pits called craters.

Orbit And Spin

Like all planets, Uranus has two types of motion: orbit and spin. Uranus orbits, or travels

around, the sun. It takes about 84 Earth years to complete one orbit. In other words, a year on

Uranus equals about 84 Earth years.

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Uranus spins about its center in an unusual way. It is tilted so that it spins nearly on its side.

Also, Uranus is one of the few planets in the solar system to spin in a clockwise direction. Most

of the planets spin in the opposite direction. Uranus completes one rotation in about 17 hours,

so a day on Uranus lasts about 17 hours.

Observations And Exploration

Uranus is a huge planet, but it is so far away that people on Earth cannot see it without a

telescope. The astronomer William Herschel discovered Uranus using his telescope in 1781.

Uranus’ rings were discovered in 1977.

Even with the more powerful telescopes available in the 21st century, the distant planet is

difficult to observe in great detail. Much of what is known about it comes from close-up

photographs and measurements taken by Voyager 2. The unmanned U.S. spacecraft Voyager

2 flew by Uranus in 1986. It is the only spacecraft that has visited the distant planet.

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