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Uranus, the seventh planet from the sun, is the third-largest planet in the solar system,
after Jupiter and Saturn, with a diameter about 4 times the Earth's. Like the two larger
planets, Uranus is made largely of hydrogen and helium, but it also has many more icy
compounds made of water, ammonia, and methane, as well as other materials. Because of this,
Uranus is sometimes referred to as an "ice giant."
Uranus has the coldest atmosphere of any planet in the solar system, even though it is not
the farthest planet from the sun, with temperatures of about -371 degrees F or -224 Celsius. Unlike
Neptune, Uranus does not generate much internal heat. As a result, the weather on Uranus is
mostly calm when compared to the feverish activity of the other gas giants. In fact,
at one time Uranus was called 'the most boring planet in the solar system!'
The exception is the weather produced during seasonal changes. Uranus is more than 1.7
billion miles or about 3 billion kilometers from the sun, and traces such a huge path
around it that it takes 84 Earth years for Uranus to travel once around the sun. That
means that each season lasts for 21 years! In addition, Uranus is tilted much, much more
than the earth is. Uranus is the only planet in the solar system to be tilted so far that
it is rotating nearly sideways in its orbit! It is also one of only two planets in the
solar system - Venus is the other - to rotate in a direction opposite most of the planets.
This tilt makes the seasonal changes on Uranus extreme. During winter and summer, even though
the planet continues to rotate at regular 17-hour intervals, the summer side faces constantly
towards the sun, and the winter side stays in complete darkness. As the seasons change
to spring and fall and sunlight touches parts of the planet that haven't seen light for
21 years, the weather begins to change, causing an increase in storms and cloud formations,
with winds of up to 560 miles or 900 kilometers per hour recorded.
Only one spacecraft has ever flown by Uranus: Voyager 2, which passed the planet in 1986.
It just so happened that at that time the northern hemisphere of Uranus was in winter,
and so the images that Voyager 2 recorded were of an almost featureless blue planet.
In the years since then, the seasons have changed, and Uranus has revealed more interesting
weather patterns.
Although it is possible to see Uranus with the unaided eye in good viewing conditions,
it was never recognized by ancient peoples as a planet because it was so dim and moved
so slowly. It was Sir William Herschel who first recognized that it was not a star in
1781, making Uranus the first planet to be discovered with a telescope. At first, Herschel
named it 'Georgium Sidus,' or 'George's Star' in honor of King George III, but other astronomers
felt that the planet's name should stay in line with the mythological origins of the
other planets. The name Uranus was selected, after the Greek god of the sky, and less than
70 years after its discovery Uranus is what the planet was universally called.
Uranus has a system of 13 faint rings, and 27 moons circling around it. William Herschel
first claimed to see a ring around Uranus in 1789, but rings were not confirmed until
nearly 200 years later in 1977. Herschel also discovered two of the planet's 5 large moons.
Some of Uranus's small moons were still being discovered as recently as the early 21st century!
There is no knowing what future discoveries are in store from this mysterious planet,
but scientists continue to study and observe in an attempt to understand it.
I hope you enjoyed learning about Uranus, the sideways planet. Goodbye till next time!