Study Guide Key for Chapter 2 - The Solar System
1. The hottest of the planets is Venus because of the greenhouse effect. The inner planets are
rocky and solid because gravity pulled the denser materials towards the Sun.
2. The outer planets, which are also known as the gas giants. The interiors of the outer planets are
mainly liquid instead of solid. In general, the outer planets have thick gas and liquid layers
covering a small solid core.
3. The inner planets—Mercury, Venus, Earth, and Mars—are the planets closest to the Sun.
4. A meteor is a streak of light in Earth’s atmosphere made by a glowing meteoroid.
5. A meteorite is a meteoroid that strikes a planet or a moon.
6. Some astronomers think the strength of Jupiter’s gravitational field might have caused the
chunks to collide so violently that they broke apart instead of sticking together.
7. Mercury has no atmosphere.
8. As a comet moves closer to the Sun, it heats up and can develop a bright tail.
9. Evidence suggests that ____ originate in the Oort Cloud located beyond the orbit of Pluto. Longperiod comets come from a zone called the Oort cloud.
10. Jupiter is the largest planet in the solar system, is the fifth planet from the Sun, and has colorful
clouds.
11. The greenhouse effect occurs when a planet’s atmosphere traps solar energy and causes the
surface temperature to increase.
12. The smallest planet and the planet closest to the Sun is Mercury.
13. Why did the artists for both of these illustrations feel it necessary to represent the inner planets
with a pulled out piece? Since the outer planets are as much as 30 AU from the Sun, and the
inner planets as little as 0.39 AU from the Sun, it is very hard to represent them all in a
meaningful way using the same scale.
14. The basic astronomical unit based on the average distance from Earth to the Sun.
15. The basic shape of every planet’s orbit is an ellipse which is a special kind of rounded shape that
has two foci equidistant from the center of the figure.
16. The gravity of the Sun keeps the objects in orbit. While the gravity of the objects does exert
some force, it is negligible compared to the gravity of the Sun.
17. The outer planets are primarily made of hydrogen and helium, materials that are usually gases
on Earth.
18. Ring systems and moons orbit all of the outer planets. Scientist do not know what materials
make up the cores of the outer planets, but they think they are small solid cores.
19. All of the dwarf planets are smaller than Earth’s Moon, which is in turn smaller than Mercury
and Earth.
20. A meteorite is a meteoroid that strikes a planet or a moon. The depression it makes when it hits
is an impact crater.
Name the planet that is being described below.
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dark-colored storms and 13 moons ________________
iron oxide and polar ice caps ______________
largest planet _______________
most complex ring system ________________
axis of rotation tilted on its side _________________
greenhouse effect causes extremely high surface temperatures _________________
smallest planet _______________
liquid water oceans _______________
29. Match the planets below with the letters labeling the planets.
30. Mercury is too small to have strong enough gravity to hold an atmosphere.