uranus

an icy bluegreen ball

Like Jupiter and Saturn, Uranus is composed mainly of hydrogen and helium, with an outer gas layer that gives way to liquid on the inside. Uranus has a higher percentage of icy materials, such as water, ammonia (NH3 ), and methane (CH4 ), than Jupiter and Saturn. When sunlight reflects off Uranus, clouds of methane filter out red light, giving the planet a blue-green color. There are bands of clouds in the atmosphere of Uranus, but they are hard to see in normal light, so the planet looks like a plain blue ball.

the sideways planet

Most of the planets in the solar system rotate on their axes in the same direction that they move around the Sun. Uranus, though, is tilted on its side, so its axis is almost parallel to its orbit. In other words, it rotates like a top that was turned so that it was spinning parallel to the floor. Scientists think that Uranus was probably knocked over by a collision with another planet-sized object billions of years ago.

rings and moons of uranus

Uranus has a faint system of rings (Figure 1.1). The rings circle the planets equator, but because Uranus is tilted on its side, the rings are almost perpendicular to the planets orbit. This image from the Hubble Space Tele- scope shows the faint rings of Uranus. The planet is tilted on its side, so the rings are nearly vertical. Uranus has 27 known moons and all but a few of them are named for characters from the plays of William Shakespeare. The five biggest moons of Uranus Miranda, Ariel, Umbriel, Titania, and Oberon are shown in Figure 1.2. These Voyager 2 photos have been resized to show the relative sizes of the five main moons of Uranus. Click image to the left or use the URL below. URL:

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uranus

Uranus (YOOR-uh-nuhs) is named for the Greek god of the sky. From Earth, Uranus is so faint that it was unnoticed by ancient observers. William Herschel first discovered the planet in 1781. Although Uranus is very large, it is extremely far away, about 2.8 billion km (1.8 billion mi) from the Sun. Light from the Sun takes about 2 hours and 40 minutes to reach Uranus. Uranus orbits the Sun once about every 84 Earth years. Uranus has a mass about 14 times the mass of Earth, but it is much less dense than Earth. Gravity at the surface of Uranus is weaker than on Earths surface, so if you were at the top of the clouds on Uranus, you would weigh about 10% less than what you weigh on Earth.

instructional diagrams

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questions

who first discovered uranus?

a) galileo galilei

-->  b) william herschel

c) johannes kepler

d) ancient shepherds

in the planetary lineup, uranus is

-->  a) #7

b) 3rd from the outermost.

c) just before pluto.

d) right after mars.

if your grandfather is 73 years old, he has been alive for one year on uranus.

a) true

-->  b) false

the composition of uranus is

a) the same as saturn and jupiter.

b) the same as neptune.

-->  c) higher in ices, such as water, ammonia and methane.

d) higher in carbon dioxide and nitrogen.

uranus is a blue-green color because

a) clouds of carbon dioxide filter out the red light.

b) clouds of carbon dioxide filter out the blue and green light.

-->  c) clouds of methane filter out the red light.

d) clouds of methane filter out the blue and green light.

gravity is stronger on uranus than earth.

a) true

-->  b) false

uranus is unusual among the outer planets because

-->  a) it is tilted on its side.

b) its rings are the same color as the planet.

c) it doesnt have any moons.

d) all of these.

uranus has _ known moons, most of which are named for characters from __.

a) 33; cs lewis

b) 23; lord of the rings

c) 15; harry potter

-->  d) 27; shakespeare

uranus may have been hit by struck by an enormous object billions of years ago.

-->  a) true

b) false

uranus rings

a) circle the planets poles.

-->  b) are almost vertical.

c) are visible from earth with a very good telescope.

d) all of these.

diagram questions

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