The seventh planet from the sun, Uranus is the larger of the ice giants. The blue body contains an icy atmosphere that, like Neptune, differs dramatically from the other large planets.
"Uranus and Neptune are unique in our solar system. They're very different planets than the other ones we think of," planetary scientist Amy Simon said on NASA's Gravity Assist podcast. "Part of the reason we call them ice giants is because they actually have a lot of water ice. So, while some of the other gas giant planets are mostly hydrogen and helium, they're predominately water and other ices."
Although Uranus, discovered in 1781, is only four times the physical size of Earth, it is significantly more massive, weighing in at 86 septillion kilograms (just under one trillion trillion trillion). That makes it more than 14.5 times as massive as our rocky home.
The planet has a volume of 6.83x1013 cubic kilometers.
The density of Uranus is 1.27 grams per cubic centimeter, making it the second least dense planet in the solar system. Its low density indicates that it is predominantly composed of ice rather than gas. The icy composition of Uranus and Neptune both differ from the heavier gas giants, Jupiter and Saturn, and have caused them to be labeled "ice giants." The distance to Uranus from the sun is significant, resulting in the coldest atmosphere in the solar system and accounting for the icy temperatures.
"These planets formed much farther out in the solar system where there was a lot of ices available," Simon said. "And they didn't quite form as big as, say, Jupiter or Saturn. So, they couldn't pull in quite as much gas. And so, that's kind of part of why we believe they're so different."