Voyager 2 captured the planet during its solstice, when one pole was bathed in sunlight and so kept a constant temperature. But follow-up observations have since shown that there's more there than initially meets the eye. The craft came as near as 50,600 miles to Uranus' cloud tops in 1986, giving scientists their first detailed peek at both the planet and its many curious moons.ĭuring that encounter, Voyager 2 snapped what is perhaps the most famous picture of Uranus-a pale turquoise orb in a sea of darkness. Only one spacecraft, Voyager 2, has ever flown by Uranus at close range. Photograph courtesy NASA Beneath the blue The seventh planet from the sun is so distant that it takes 84 years to complete one orbit. The first planet found with the aid of a telescope, Uranus was discovered in 1781 by astronomer William Herschel. That sets the planet's auroras out of line, making them appear far from the poles, unlike those on Earth. It's tipped nearly 60 degrees from the axis of rotation. Like Venus, Uranus has what's known as a retrograde rotation, turning on its axis in the opposite direction to the rest of the planets.Īlso topsy turvy is Uranus' magnetosphere, the magnetic field enveloping the gaseous world. And that's not the only strange thing about its spin. Thanks to its sideways turn, Uranus has some wild seasons, with the sun blazing across each pole for 21 Earth-years at a time while the opposing side lingers in the pitch blackness of space. Scientists believe that this unexpected tilt is the result of a massive collision with something the size of Earth far in the planet's past. The gas giant is tipped on its side, spinning on its axis at nearly a right angle to its orbital path around the sun, which requires a lengthy 84 Earth-years to complete. One particularly curious feature of Uranus is its off-kilter positioning. While Saturn wears the crown for the least dense planet in our celestial family, Uranus is not far behind: Most of its mass is made up of an icy dense fluid of water, ammonia, and methane. Trace amounts of hydrogen sulfide also hint that, if you could visit this distant place without a spacesuit, the planet would smell like rotten eggs. The rest of planet's atmosphere is largely made of hydrogen and helium, with scant amounts of ammonia, water, and methane. Uranus owes its vibrant blue-green hues not from unusual oceans but from an upper atmosphere flush with methane, which absorbs the sun's red light and scatters blue light back to our eyes. Like Saturn, Jupiter, and Neptune, Uranus is a big ball of gas, often called a jovian or gas giant world. But it is actually the third-largest planet in our solar system, and is roughly four times wider than Earth. The planet Uranus was so hard to find in part because it is a whopping 1.8 billion miles away. Instead, it got its official name from the Greek god of the sky, Uranus, who was both son and husband to Gaea, the goddess of Earth. When it was accepted as a planet years later, Herschel lobbied to call the discovery Georgium Sidus after King George III. In March 1781 British astronomer Sir William Herschel spotted the glinting object in the sky, initially mistaking it for a comet. Uranus was the first of three planets in our solar system discovered thanks to the invention of the telescope. But there's a lot to love about the icy giant, from its 13 rings to its 27 known moons to the fact that it may even rain diamonds from its hazy atmosphere. Uranus, the seventh planet from the sun, may initially look like a bland, blue-green ball.
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