Download GENERAL INFORMATION ON URANUS

URANUS
Uranus is the seventh planet from the sun in our solar system. This huge, icy planet is
covered with clouds and is encircled by a belt of 11 rings and 27 known moons. Uranus'
blue color is caused by the methane (CH4) in its atmosphere; this molecule absorbs red
light.
ROTATIONAL AXIS
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. For example: ‘summer’ in the northern hemisphere means 21 years of unending
sunlight!!! ‘Winter’ has the opposite- this season in the northern hemisphere means 21 years of frigid darkness!
Because of its almost-perpendicular axis orientation, there is a debate over which of Uranus' poles is its north pole. This debates
leads to yet another: Is Uranus spinning in a retrograde orbit (like Venus) or not (like the other planets)? A catastrophic collision
with another large body eons ago may have tipped Uranus over on its side.
SIZE
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).
MASS AND GRAVITY
Uranus' mass is about 8.68 x 1025 kg. This is about 14 times the mass of the Earth. 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.
LENGTH OF A DAY AND YEAR ON URANUS
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' ORBIT AND DISTANCE FROM THE SUN
Uranus is over 19 times as far from the Sun as the Earth is; it averages 19.18 A.U.
At aphelion (the farthest point in its solar orbit) it is 1,850,000,000 miles (3,003,000,000 km) from the Sun. At perihelion (the
closest point in its solar orbit) it is 1,700,000,000 miles (2,739,000,000 km) from the Sun.
TEMPERATURE
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 giants, Jupiter, Saturn and Neptune).
PLANETARY COMPOSITION AND ATMOSPHERE
Uranus is a frozen, gaseous planet with a molten core. Uranus' atmosphere consists of 83% hydrogen, 15% helium and 2%
methane.
RINGS
Uranus and its rings photographed by an infrared camera.
Uranus has a belt of 11 faint, narrow rings 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.
MOONS
Uranus has at least 27 moons, 5 which are quite large. Two were discovered by Wm. Herschel in 1781, two by Wm. Lassell in 1851,
and one by G. Kuiper in 1948. The others were discovered much later with the assistance of the Voyager spacecraft. Titiana is
the largest moon, which astronomers believe once had a liquid ocean!
DISCOVERY OF URANUS
Uranus was discovered by the British astronomer William Herschel on March 13, 1781. Herschel also discovered two of the
moons of Uranus (Titania and Oberon) and some of the moons of Saturn.
Oberon, the second largest
moon of Uranus. Photo
taken by NASA's Voyager
mission in 1986.
URANUS' NAME AND SYMBOL
This planet was originally named in 1781 by the British astronomer William Herschel - he called it Georgium Sidus (meaning "the
Georgian planet") to honor the King George III of England. The name was later changed to Uranus, the ancient mythological god
of the sky, Ouranos. The name Uranus was suggested by the German astronomer Johann Elert Bode.
STALKERS
Scientists in 2006 discovered that there are three asteroids that share orbits with Uranus, much like the co-orbital moons of
Saturn. Astrophysicists have confirmed that Crantor, a large asteroid with a diameter of 70 km has an orbit similar to that of
Uranus and takes the same amount of time to orbit the Sun. Researchers have demonstrated for the first time that this and a
further two objects of the group of the Centaurs, (Asteroids that exist between the orbits of Jupiter and Neptune), are co-orbital,
(share the orbit), with Uranus. The scientists calculate that the orbits of these three objects associated with Uranus could
remain stable for a few million years. In astronomical terms this is not very long.
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SPOP!
1)
Who discovered Uranus? In which year was it discovered?
2) Describe the tilt of Uranus on its axis. How does this affect seasons?
3) How much would a 120 pound person weigh on Uranus?
4) What did astrophysicists discover about Uranus in 2006?
5) What is a ‘Centaur’?
6) What does it mean if two objects are co-orbital?
7) How many moons does Uranus have? Which is the largest?
8) What was the original name of Uranus? If you had the opportunity to name a planet, what would you name it, and why?