Lesson 1 | The Structure of the Solar System



Name Date Class

LESSON 1

The Structure of the Solar System

Directions: On each line, write the term from the word bank that correctly replaces the underlined words in each

sentence. Use each term only once. NOTE: You may need to change a term to its plural form.

asteroid astronomical unit comet orbit

period of revolution period of rotation star

1. Many objects, including planets, travel around the Sun.

2. Orbiting objects made of gas, dust, and ice come from the

outer parts of the solar system.

3. The Sun is a(n) structure in space made of gases in which

nuclear fusion reactions occur.

4. In 365 days, Earth completes a(n) full journey around

the Sun.

5. In 24 hours Earth completes a(n) full turn, also called a

complete spin.

6. Millions of small, rocky objects orbit the Sun between the

orbits of Mars and Jupiter.

7. A(n) distance equal of about 150 million km is the average

distance from Earth to the Sun.

The Solar System 9

Name Date Class

LESSON 1

The Structure of the Solar System

Earth inner planets Jupiter Mars

Mercury Neptune outer planets Saturn

Sun Uranus Venus

Directions: Label this diagram by writing the correct term from the word bank on each line.

The Solar System 13

Name Date Class

LESSON 1

The Structure of the Solar System

Directions: On each line, write the term from the word bank that correctly completes each sentence. Some terms

may be used more than once or not at all.

astronomical closer comet elliptical energy

farther faster foci focus gas giants

gravitational inner outer planet revolve

rotate slower solar system stars Sun

The night sky offers a fascinating view into space. Most of the specks of light in

the night sky are (1.) . They exist far beyond our

(2.) . The largest object in our solar system is the

(3.) , which produces an enormous amount of

(4.) . The Sun also applies a(n) (5.)

pull on the planets. When you look into the night sky, you might see light reflected off a(n)

(6.) , such as Venus.

Objects in space (7.) around the Sun along a

stretched-out circle called a(n) (8.) orbit. Planets also

(9.) , or spin. There are four (10.)

planets that are made up mostly of solid rocky materials. These objects are spherical and

have a mass larger than the total mass of all other objects whose orbits are nearby. There

also are four (11.) planets made of gases, including helium and

hydrogen. These four planets are sometimes termed (12.) .

Distance in space is measured in (13.) units. A planet’s

speed changes as it orbits the Sun. A planet that is close to the Sun moves

(14.) than a planet that is far from the Sun. Also, planets that

are (15.) from the Sun have longer periods of revolution than

planets that are closer to the Sun. The shape of a planet’s orbit is determined by two

(16.) points. These (17.) are equal

distances from the center of the ellipse.

14 The Solar System

Name Date Class

LESSON 1

The Structure of the Solar System

Key Concept How are the inner planets different from the outer planets?

Directions: On the line before each description, write the letter of the term that matches it correctly. Some terms

will be used more than once.

1. four planets closest to the Sun

2. nonspherical rocky objects

3. the largest object in the solar system

4. Jupiter, Saturn, Uranus, and Neptune

5. one trillion of them might orbit the Sun

6. a source of light energy

7. planets made of mostly solid rocky materials

8. Ceres, Pluto, Eris, and Makemake

9. planets made mainly of ice and gases

10. Mercury, Venus, Earth, and Mars

11. sometimes called gas giants

12. where nuclear fusion reactions occur

13. planets much larger than Earth

A. Sun

B. inner planets

C. asteroids

D. outer planets

E. dwarf planets

F. comets

16 The Solar System

Name Date Class

LESSON 1

The Structure of the Solar System

Key Concept What is an astronomical unit, and why is it used?

|The Astronomical Unit (AU) |

|Planet |Average Distance (km) |Average Distance (AU) |

|Mercury |57,910,000 |0.39 |

|Venus |108,210,000 |0.72 |

|Earth |149,600,000 |1.00 |

|Mars |227,920,000 |1.52 |

|Jupiter |778,570,000 |5.20 |

|Saturn |1,433,530,000 |9.58 |

|Uranus |2,872,460,000 |19.20 |

|Neptune |4,495,060,000 |30.05 |

Directions: Use the table to complete each statement.

1. Astronomical units are used for measuring in space because

.

2. The closest inner planet to the Sun is . In astronomical

units, this planet is from the Sun.

3. The closest outer planet to the Sun is . In astronomical

units, this planet is from the Sun.

4. In astronomical units, Earth is from the Sun.

5. An astronomical unit is given as the average distance from the Sun because orbits are

not perfect circles; they are .

6. Neptune is about times farther from the Sun than Jupiter,

and Jupiter is about times farther from the Sun than Earth.

18 The Solar System

Name Date Class

LESSON 1

The Structure of the Solar System

Key Concept What is the shape of a planet’s orbit?

Directions: Circle the phrase that correctly completes the sentence.

1. Planets revolve around the Sun

2. An ellipse is like a

3. A planet moves slower

4. A planet’s speed increases

5. Planets that are farther from the Sun

6. The shape of a planet’s orbit

The Solar System 19

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Content Vocabulary

Content Practice A

Content Practice B

Key Concept Builder

Key Concept Builder

Key Concept Builder

A. in ellipses.

B. in perfect circles.

A. figure eight.

B. stretched-out circle.

A. when it is farther from the Sun.

B. when it is closer to the Sun.

A. as it gets closer to the Sun.

B. as it gets closer to either focus.

A. have longer periods of rotation.

B. have longer periods of revolution.

A. depends on its speed.

B. is determined by the foci.

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