Emerald Robinson: Hi! I'm Emerald Robinson. In this "What Is" video we're going to explore the odd world of the planet Uranus. Uranus was named after the Greek god of the sky after its discovery in 1781. It's the seventh Planet from the Sun, making it one of the outer planets in the solar system. Uranus also has 13 very faint dark rings and 27 moons, most of which are named for Shakespearean characters.
Uranus' diameter is 31,000 miles, almost four times that of Earth. Despite the size difference, Uranus' gravity is only eighty six percent as strong. A person weighing 100 lbs. on Earth would weigh just 89 lbs. on Uranus.
The atmosphere on Uranus is mostly hydrogen and helium, with a small amount of methane and traces of water and ammonia. Sunlight passes through the atmosphere and is reflected back out by Uranus' cloud tops. The methane gas absorbs the red portion of the light, giving it its blue-green color.
Like the other planets, Uranus has an elliptical orbit. On average, it is 1.
8 billion miles from the sun, and takes 84 Earth years to complete one orbit. Uranus is unique among the planets because its axis lies nearly level with its path around the sun, causing it to appear to be rotating on its side. A day on Uranus takes a little over 17 Earth hours.
One theory for Uranus' unique orientation is that a powerful collision with another celestial body knocked it off its original axis sometime during the formation of the universe. This, along with its 84 year long orbit, causes Uranus' seasons to last over twenty years. The tilted axis also means its north and south poles alternate between direct sunlight or complete darkness every 42 years!
The upper atmosphere of Uranus is the coldest in the Solar System, with a minimum temperature of -371 degrees F. And the wind speeds on Uranus can reach an astounding 560 miles per hour!
Side-winding Uranus is the coldest planet in our solar system, even though it's not the furthest away from the Sun. That honor goes to Neptune.