Uranus :
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Word Bank :
Herschel
rings
Jupiter
seasons
1977 |
gravity
axis
heat
blue
91 |
moons
Sun
mass
gas giant
Greek |
Uranus is the seventh planet from the Sun in our Solar System. This huge, icy gas-giant is covered with clouds and is encircled by a belt of 11 faint rings and 18 moons . Uranus' blue color is caused by the methane (CH 4 ) in its atmosphere; this molecule absorbs red light. Uranus was discovered by the British astronomer William Herschel on March 13, 1781. It was named for the ancient Greek god of the sky.
Uranus' 11 faint, narrow rings are composed of rock and dust. They circle Uranus is very elliptical orbits. These rings are only a fraction of the size of Saturn's rings, and were only discovered in 1977 .
Uranus is about 31,690 miles (51,118 km) in diameter. This is about 4 times the diameter of the Earth. This gas giant is the third-largest planet in our Solar System (after Jupiter and Saturn).
Each day on Uranus takes 17.9 Earth hours. A year on Uranus takes 84.07 Earth years; it takes 84.07 Earth years for Uranus to orbit the Sun once.
Uranus' rotational axis is strongly tilted on its side (97.9°). Instead of rotating with its axis roughly perpendicular to the plane of its orbit (like all the other planets in our Solar System), Uranus rotates on its side (along its orbital path). This tipped rotational axis gives rise to extreme seasons on Uranus. The mean temperature on the surface of Uranus' cloud layer is -350°F (59 K). Uranus radiates very little heat in comparison with the other gas giant planets.
Uranus' mass is about 8.68 x 10 25 kg. This is about 14 times the mass of the Earth, but the gravity on Uranus is only 91% of the gravity on Earth. This is because it is such a large planet (and the gravitational force a planet exerts upon an object at the planet's surface is proportional to its mass and to the inverse of its radius squared). A 100-pound person on Uranus would weigh 91 pounds.
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