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Directed Reading A
Section: The Nine Planets
______ 1. What does the word planet mean?
a. sky
c. stars
b. wanderers
d. solar system
______ 2. Ancient astronomers knew that planets were
a. wandering stars.
c. physical bodies.
b. full of life.
d. easy to explore.
______ 3. What scientific instrument first made it possible to study the stars and
planets?
a. gyroscopes
c. spectroscopes
b. microscopes
d. telescopes
______ 4. Which famous 17th century scientist used a telescope to explore the
sky?
a. Copernicus
c. Galileo
b. Charles Darwin
d. Isaac Newton
OUR SOLAR SYSTEM
5. Our solar system consists of the
the
,
, and many smaller objects.
6. What makes up the Saturn system?
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Directed Reading A continued
MEASURING INTERPLANETARY DISTANCES
______ 7. The average distance between the Earth and the sun is
a. the light-year.
c. the kilometer.
b. the astronomical unit.
d. the parsec.
______ 8. Another way to measure distances in space is by using
a. a tape measure.
c. a globe.
b. a road map.
d. the speed of light.
9. The amount of time it takes light to travel around the Earth seven and a half
times is
.
10. The distance light travels in 1 min is called a(n)
.
11. How many light-minutes are there in one astronomical unit?
THE DISCOVERY OF THE SOLAR SYSTEM
______12. Which new bodies were discovered after the telescope was introduced
during the 17th century?
a. Uranus and Pluto
c. Uranus and its moons
b. Neptune and Uranus
d. the moons of Jupiter and Saturn
______13. Which was the last planet discovered during the 20th century?
a. Mercury
c. Pluto
b. Neptune
d. Uranus
14. Which eight bodies were known to make up the solar system before the
invention of the telescope?
THE INNER AND OUTER SOLAR SYSTEMS
______15. How many planets are in the inner solar system?
a. 10
c. 4
b. 15
d. 3
______16. How many planets are in the outer solar system?
a. 6
c. 11
b. 5
d. 20
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Directed Reading A continued
17. To which of these two groups does planet Earth belong?
18. The inner planets are also called
planets because
their surfaces are dense and rocky.
19. Name the planets of the inner solar system.
20. Name the planets of the outer solar system.
21. Why are most of the outer planets called gas giants?
22. How do the inner planets differ from the planets of the outer solar system?
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Answer Key
Directed Reading A
SECTION: THE NINE PLANETS
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
16.
17.
18.
19.
20.
21.
22.
B
C
D
C
sun; planets
The Saturn system is made up of the
planet Saturn and the several moons
that orbit it.
B
D
1 second
light minute
There are 8.3 light minutes in one
astronomical unit.
D
C
the sun, Mercury, Venus, Earth, Mars,
Jupiter, Saturn, and the Moon
C
B
the inner solar system
terrestrial planets
Mercury, Mars, Earth, Venus
Jupiter, Saturn, Uranus, Neptune, Pluto
They are very large planets that are
composed mostly of gases and do not
have any known solid surfaces.
They are made of different materials.
15. D
16. Because Venus is only slightly smaller,
17.
18.
19.
20.
21.
22.
23.
24.
25.
26.
27.
SECTION: THE OUTER PLANETS
1. gas giant
2. Pluto is dense, rocky, and icy while the
SECTION: THE INNER PLANETS
1. B
2. The inner planets are smaller, denser,
and rockier than the outer planets.
3. C
4. period of rotation
5. because its period of rotation is so
slow
6. C
7. D
8. A
9. B
10. A
11. D
12. B
13. C
14. C
less massive, and less dense than
Earth.
prograde
retrograde
Earth is located at just the right
distance from the sun to keep its
water from freezing and cool enough
to keep its water from boiling away.
the atmosphere, the oceans, and the
biosphere
C
B
C
Mars is a cold planet because it has a
thin atmosphere that cannot trap heat
and it is located much farther out from
the sun.
Olympus Mons
The difference in the chemical
composition of Mars has kept the
Martian crust from shifting like Earth’s
so the Martian volcanic system keeps
building up in the same spots.
The Twin Rovers were designed to help
determine whether life ever existed on
Mars and to help prepare for human
exploration missions to Mars.
others are giant balls of gas.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
A
C
B
C
As depth and pressure increases,
hydrogen gas turns into liquid form.
Deeper still, the liquid hydrogen
changes into a liquid, metallic state.
C
rings, moons, atmosphere
C
B
B
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