Night Sky: Time to write about Uranus


Over the years I have written about the Sun, moon, Pluto and five other planets. Now, it is time to write about Uranus. It is an interesting planet with an interesting name. How many of us pronounce it the crazy way instead of the proper way?

Uranus is the seventh planet from the Sun and the third largest in our solar system. It is 1.786 billion miles from the Sun and takes slightly more than 84 years to orbit the Sun. There are 27 moons and 13 sparse rings surrounding it. Uranus is twice as far from the Sun as Saturn which is why it is so pale for us to observe, although it is visible with unaided vision.

It was the first planet to be discovered with a telescope. This happened in 1781 by William Herschel. Officially, it has been observed since 129 BC, but because it looked so small and pale, it was thought to be a star. The first astronomer to officially observe it was the Greek astronomer Hipparchus.

It is named for Uranus who was the Grand Father of Zeus. Our planets have been named after ancient Greek and Roman gods. Uranus was also the father of Saturn. It is the only planet in our solar system named after a god from Greek mythology rather than the Roman version.

Because Uranus is so far away, we knew little about it until the Voyager 2 flew by it in 1986. Nothing has flown by it since then.

Its pale blue color comes from the methane gas in its atmosphere. Uranus contains three layers. There is a rocky core, an icy mantle in the middle, and an outer layer of hydrogen and helium. Although it is four times larger than Earth, its surface gravity is less than Earth's.

Our early solar system was a violent place with planets smashing into each other pushing one another into different orbits. Some were probably spun out of the solar system or into the Sun. It is thought its sparse ring system and all its moons probably came from these collisions.

An interesting fact about Uranus is that it rotates on its side. It is tipped over 98 degrees, so its moons and rings encircle it from top to bottom. Also, its spin is retrograde, so it orbits the Sun in the opposite direction that Earth and most planets do. Only Venus orbits the Sun that way too.

It rotates fast as 17 hours, 14 minutes, and 24 seconds. There are four seasons like us, but each one lasts 21 years. Because it is on its side it only appears to rotate once in its orbit. It does not turn in its orbit. Remember that it spins on its side. So, the North Pole faces the Sun 21 years, then the side faces the Sun 21 years. The South Pole faces the Sun for 21 years and then the other side faces the Sun for 21 years.