Download Chapter 21 A Family of Planets

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Name
SECTION 1
Class
Date
Our Solar System continued
The Inner Planets
TAKE A LOOK
Earth
4. Identify Which of the
inner planets is closest to
the sun?
Mercury
Venus
Sun
5. Identify Which of the
inner planets is furthest from
the sun?
Mars
THE OUTER PLANETS
The outer solar system contains four planets: Jupiter,
Saturn, Uranus, and Neptune. The outer planets are very
different from the inner planets.
The outer planets are very large and are made mostly
of gases. Therefore, Jupiter, Saturn, Uranus, and Neptune
are sometimes called the gas giant planets, or simply the
“gas giants.”
The distances between the outer planets are much
larger than the distances between the inner planets. For
example, the distance between Jupiter and Saturn is
much larger than the distance between Mars and Earth.
The figure below shows the orbits of the outer planets.
Critical Thinking
6. Compare Give two
differences between the
inner solar system and the
outer solar system.
The Outer Planets
Neptune
Jupiter
Inner
Planets
TAKE A LOOK
Saturn
7. Identify What planet is
farthest from the sun?
Uranus
Copyright © by Holt, Rinehart and Winston. All rights reserved.
Interactive Textbook
407
A Family of Planets
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Name
SECTION 3
Class
Date
The Outer Planets continued
A SMALL WORLD
Pluto is made of rock and ice and has a thin
atmosphere made of methane and nitrogen. Scientists do
not know if Pluto formed along with the planets.
AN UNUSUAL ORBIT
The shape of Pluto’s orbit is different from the shapes
of the orbits of the outer planets. As shown in the figure
below, sometimes Pluto is closer to the sun than Neptune
is. At other times, Neptune is closer to the sun.
3ATURN
*UPITER
TAKE A LOOK
10. Compare How is Pluto’s
orbit different from the orbits
of the outer planets?
5RANUS
.EPTUNE
0LUTO
The shape of Pluto’s orbit is very different
from the orbits of the outer planets.
Facts About Pluto
Distance from sun
39.5 AU
Period of rotation
6 days, 10 hours
Period of revolution
248 Earth years, 4 days
Diameter
2,390 km
Density
1.75 g/cm3
Surface gravity
6% of Earth’s
A LARGE MOON
Pluto’s moon, Charon, is more than half the size of
Pluto. From Earth, it is hard to separate the images of
Pluto and Charon because they are so far away. Charon
may be covered by frozen water.
Critical Thinking
11. Infer How do you think
scientists learned that Pluto
has a moon if it is difficult to
separate their images?
Copyright © by Holt, Rinehart and Winston. All rights reserved.
Interactive Textbook
419
A Family of Planets
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