Outer Planets Quiz/Tutorial

1. What is the name of planet A in the above picture?
C).. Uranus.

2. What is the name of planet B in the above picture?
B)... Saturn.

3. The planets shown in the figure are sometimes called the outer planets. Why?
A)...We see only their outer layers.
B)...They lie in the outer part of the Solar System.
C)...They were discovered by the Dutch astronomer Wihelm Outer.
D)... They lie high above the Solar System and the Earth's orbit.
E)... They lie in the outer part of galaxy.

4. The average density of an object is defined as its
A)...mass X volume.
C)... mass + volume.
E)... radius cubed.

You can find a planet or star's average density by dividing its mass M by 4R3/3, where R is its radius. In doing such calculations you need to be SURE to use the proper units. Density is often expressed in grams per cubic cm. Therefore the mass must be in grams and the radius in cm.

For example, suppose we want to calculate the density of Uranus. We therefore need its mass and radius which we can find in a table of properties of planets. Its mass is 8.68x1025 kg. Its radius is 25,559 km. Round this off in the following to 2.6x104 km.

We first convert the mass to grams. One kg = 1000 grams.

Therefore to convert Kgs to gms, simply multiply by 1000 = 103.

5. What is Uranus's mass in gm?
B)... 8.68x1075.

We must next convert the radius in km to a radius in cm.

1 km = 1000 meters and 1 meter = 100 cm.

Therefore 1 km = 1000x100 =105 cm.

Thus, to convert km to cm, multiply by 105.

6. What is Uranus' radius in cm?
A)... 2.6x10-1.
B)... 2.6x109.
C)... 2.6x1020

To now find the density of Uranus. we insert the mass and radius into the formula

= M/(4R3/3)

= 8.68x1028/(4(2.6x109)3/3)

= 8.68x1028 /(4x3.14..x(2.63x109x3/3)

= 8.68x 10 28-27/(73.6)

= 1.18 gm/cm3.

You can also find the density of an object by comparing its mass and radius to the mass and radius of an object of known density as follows: a) Increasing the mass by a given factor, increases the density by the same amount.. b) Increasing the radius by a given factor, decreases the density by the amount cubed.

For example: If its mass were the same as the Earth's but its radius were 3 times larger, its density would be 5 gm/cm3 /(33) = 5/27 = 0.185 (approx). Likewise, if its radius were the same but its mass were 3 times larger, its density would be 5 gm/cm3 X 3 = 15 gm/cm3.

7. The Earth's density is about 5 gm/cm 3. If an object's mass were ten times larger and its size the same as the Earth's, its density (in gm/cm3) would be
A)... 5.
C)... 500.
E)... 50.

Now combine these results to find the density of Jupiter.
8. Jupiter is 300 times more massive than the Earth and its radius is 10 times larger. What is its density in gm/cm3?
A)... 1.5

9. Rock has a density of about 3 gm/cm 3, and iron has a density of about 8 gm/cm 3. What does this suggest about what Jupiter is made of?
A)...It is mostly iron.
B)...It is mostly rock.
C)... It must be made of something much less dense than either rock or iron.
D)... It must be made of something much denser than either rock or iron.

10. Why do Neptune and Uranus look so blue?
A)... They have so much water in their atmospheres.
B)...We are seeing sunlight reflecting from their deep oceans.
C)...Methane in their atmosphere absorbs the red sunlight falling on the planet leaving mainly blue.
D)...They are so cold they radiate most of their light at blue wavelengths.
E)...They are so hot they radiate most of their light at blue wavelengths.

11. The planet Neptune is named for what deity?
A)...The Greek God of War.
B)...The Roman God of the Sea.
C)...The Babylonian God of the Underworld.
D)... The Aztec God of Love
E)...None of the above.

12. The planet Jupiter is named for the Roman King of the Gods. Why is this name appropriate for the planet?
A)... Jupiter's orbit is at the outer limits of the Solar System so it "sits" above the other planets.
B)...Jupiter is the biggest planet.
C)...Jupiter's clouds glow and create a halo like a crown around the planet.
D)...Jupiter is bigger than the Sun.
E)...Jupiter has the longest orbital period of any planet.

13. The planet Pluto is named for what deity?
A)...The Roman God of Night.
B)...The Roman God of War.
C)...The Roman God of the Underworld.
D)...The Aztec God of Volcanoes.
E)...Micky Mouse's dog.

14. What are some reasons that some astronomers feel that Pluto should not be considered an Jovian planet?
A)...It is not a gaseous/liquid world like Jupiter or Uranus.
B)...It is not orbiting the Sun.
C)...It is so small.
D)...All the above.
E)...Both A and C.

15. The picture of Jupiter above shows strongly colored bands. These are caused by
A)...Jupiter's magnetic field pulling the iron atoms in its atmosphere into long streamers.
B)...the gravitational tug of its moons.
C)...debris from comet chains falling into it.
D)... rising matter from deep in its atmosphere swept into streaks by its winds.
E)...shadows cast on its clouds by its rings.

16. The Coriolis effect plays a role in creating Jupiter's
A)...gravitation pull.
B)... high internal tempearture.
C)...high speed jet stream winds.
D)...low internal temperature.
E)...rapid rotation.

17.The Coriolis effect itself arises because a planet
B)...has a strong magnetic field.
C)...is far from the Sun.
D)...has a strong gravity.
E)...is composed mainly of iron.

The Coriolis Effect occurs when an object moves across the surface or through the atmosphere of a spinning planet. Even though the object moves in a straight line as seen by an observer in space, it moves along a curved path as seen by an observer on the planet. This "twists" air currents that would otherwise flow from pole to equator into currents that flow around the planet. Earth's tradewinds and westerlies (such as the jet stream) arise this way. On the outer planets they create the cloud bands we see there.

In watching the animation, note that the particle that starts at the pole moves in a straight line (vertically up the screen) but its track on the Earth is curved.

Animation showing how the Coriolis Effect Arises

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