Lesson 1 | The Structure of the Solar System

The Solar System 7

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Student Labs and Activities Page

Launch Lab 8

Content Vocabulary 9

Lesson Outline 10

MiniLab 12

Content Practice A 13

Content Practice B 14

School to Home 15

Key Concept Builders 16

Enrichment 20

Challenge 21

Lesson 1 | The Structure of the Solar System

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8 The Solar System

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How do you know which distance unit to use?You can use different units to measure distance. For example, millimeters might be used to measure the length of a bolt, and kilometers might be used to measure the distance between cities. In this lab, you will investigate why some units are easier to use than others for certain measurements.

Procedure

Launch Lab LESSON 1: 10 minutes

1. Read and complete a lab safety form.

2. Use a centimeter ruler to measure the length of a pencil and the thickness of your textbook. Record the distances below.

3. Use the centimeter ruler to measure the width of your classroom. Then measure the width of the room using a meterstick. Record the distances in the Data and Observations section below.

Data and Observations

Think About This 1. Why are meters easier to use than centimeters for measuring the classroom?

2. Key Concept Why do you think astronomers might need a unit larger than a kilometer to measure distances in the solar system?

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The Structure of the Solar SystemDirections: 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.

Content Vocabulary LESSON 1


10 The Solar System

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The Structure of the Solar SystemA. What is the solar system?

1. The in the solar system orbit the Sun.

2. The Sun and the objects that orbit it make up the .

B. Objects in the Solar System

1. The largest object in the solar system is the .

a. The Sun is a star made up mostly of gas.

b. produces enormous amounts of energy in the Sun.

c. Objects orbit the Sun because it applies forces on them.

2. Objects that orbit the Sun include planets, dwarf planets, asteroids, and

. These objects the Sun’s light.

3. A planet has a nearly shape.

a. The mass of a planet is much than the mass of nearby objects.

b. There are planets in the solar system.

c. The four planets closest to the Sun are called the planets.

d. Inner planets are made mainly from materials.

e. The four planets farthest from the Sun are called the planets.

f. Outer planets are made mostly of ice and .

g. Because the outer planets are much larger than the inner planets, they are

sometimes called .

4. A(n) is a spherical object that orbits the Sun, is not the moon of another planet, and has less mass than any of the eight planets.

5. Millions of small, rocky objects called orbit the Sun in a belt between Mars and Jupiter.

6. A(n) orbits the Sun in an oval-shaped orbit and is made of dust, gas, and ice.

Lesson Outline LESSON 1


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Lesson Outline continued

7. The is used to measure long distances in the solar system.

8. One astronomical unit (AU) is the average distance from Earth to

the .

C. The Motion of the Planets

1. One way an object in the solar system moves is by orbiting, or

, around another object.

2. The amount of time it takes an object to revolve once around the Sun is

its .

3. Objects in the solar system also spin, or .

4. The time it takes an object to rotate once is its .

5. The shape of a planet’s orbit is a(n) , which is a stretched-out circle.

a. The Sun is at one of the of the ellipse, so the distance between a planet and the Sun changes as the planet moves.

b. A planet moves when it is closer to the Sun than when it is farther away.


12 The Solar System

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How can you model an elliptical orbit?In this lab you will explore how the locations of the foci affect the shape of an ellipse.

Procedure

MiniLab LESSON 1: 20 minutes

1. Read and complete a lab safety form.

2. Place a sheet of paper on a corkboard. Insert two push pins 8 cm apart in the center of the paper.

3. Use scissors to cut a 24-cm piece of string. Tie the ends of the string together.

4. Place the loop of string around the pins. Use a pencil to draw an ellipse as shown in your textbook.

5. Measure the maximum width and length of the ellipse. Record the data in the table below.

6. Move one of the push pins so that the pins are 5 cm apart. Repeat steps 4 and 5.

Data and Observations

Eclipse

String Width Length

8 cm

5 cm

Analyze and Conclude 1. Compare and contrast the two ellipses.

2. Key Concept How are the shapes of the ellipses you drew similar to the orbits of the inner and outer planets?


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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.

Content Practice A LESSON 1


14 The Solar System

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The Structure of the Solar SystemDirections: 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.

Content Practice B LESSON 1


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The Structure of the Solar System Directions: Use your textbook to answer each question or respond to each statement.

1. The word solar comes from the Latin word sol. It means “of the sun.” The Sun is the largest object in our solar system.

What are the four types of objects that orbit the Sun?

2. For many years, scientists believed there were nine planets in our solar system because Pluto was considered to be a planet. In 2006, astronomers decided that Pluto was a dwarf planet rather than a planet.

What is the difference between a planet and a dwarf planet?

3. The Sun’s gravity keeps planets and other objects in an orbit.

What are the two ways that planets move? Describe the two motions.

4. Planetary orbits are shaped like an ellipse. The Sun is one of the foci. The other foci is empty space.

What happens when a planet travels close to the foci where the Sun is located? What happens when a planet travels close to the other foci?

School to Home LESSON 1

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16 The Solar System

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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.

Key Concept Builder LESSON 1

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

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The Structure of the Solar System Key Concept How are the inner planets different from the outer planets?

Directions: Answer each question on the lines provided.

1. What is a planet?

2. What causes objects to orbit the Sun?

3. How does the size of the outer planets differ from the size of the inner planets?

Directions: Add information to the chart to compare and contrast planets in the solar system.

Inner Planets (4) Outer Planets (4) Dwarf Planets(examples)

Names of Planets

•

•

•

•

•

•

•

•

•

•

•

•

Planet Composition

• • •

Planet Shape

• • •

Planet Mass • • •


18 The Solar System

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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.



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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 SunA. in ellipses.

B. in perfect circles.

6. The shape of a planet’s orbitA. depends on its speed.

B. is determined by the foci.

5. Planets that are farther from the Sun A. have longer periods of rotation.

B. have longer periods of revolution.

4. A planet’s speed increasesA. as it gets closer to the Sun.

B. as it gets closer to either focus.

3. A planet moves slowerA. when it is farther from the Sun.

B. when it is closer to the Sun.

2. An ellipse is like aA. figure eight.

B. stretched-out circle.


20 The Solar System

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The Structure of the Solar System

Enrichment

Applying Critical-Thinking SkillsDirections: Respond to each statement.

1. Differentiate the inner planets from the outer planets. Describe two characteristics that differ significantly for the inner and outer planets.

2. Compare Earth’s characteristics with the other planets. Conclude which one of Earth’s characteristics makes life possible. Justify your answer.

The official definition of a planet is “a large body in the solar system that orbits the Sun.” A planet has enough mass that its own gravity makes it spherical. A planet also has cleared its orbit of all objects, pulling them in by force of gravity or pushing them out of the way.

The Inner Planets Earth belongs to a group of planets in

the solar system called the inner planets. Each of these planets is unique and—except Earth—inhospitable to life. The four inner planets—Mercury, Venus, Earth, and Mars—are also called the terrestrial planets; they are solid and similar in structure and composition. During their formation, the gravity of the newly forming planets pulled heavier elements, such as iron, to their centers, while lighter elements moved toward the surface.

All the inner planets except Mercury have an atmosphere made up of water vapor, carbon dioxide, and other gases in differing ratios. Only on Earth’s atmosphere has the ratio of these gases developed in a way that is compatible with life. There is also evidence that Mars might have had

LESSON 1

liquid water millions of years ago, but not now. Only Earth has liquid water, and it has it in abundance.

The Outer PlanetsThe asteroid belt separates the inner

planets from the outer planets. Jupiter, Saturn, Uranus, and Neptune are often called the gas giants. Jupiter, Saturn, and Uranus have a solid rock core, and Neptune might also have one. Jupiter and Saturn are composed of mainly hydrogen and helium. Uranus and Neptune are composed of heavier gaseous elements. Rings of debris encircle each of the gas giants. Each of the outer planets has many moons.

The outer planets have thick atmospheres made up mainly of hydrogen and helium. They are so massive that their gravity can hold on to these lighter gases.

The outer planets are very large compared with the inner planets. For example, Jupiter is about 11 times the size of Earth. Despite their size, only two—Jupiter and Saturn—are visible to the unaided eye. Uranus and Neptune were not discovered until after the invention of the telescope.

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Challenge

The Structure of the Solar System Traveling in the Solar System

All the objects in the solar system are interesting and have some unique characteristics. Design and create a travel brochure for future space travelers in the two panels below. Select one destination among the objects in the solar system besides Earth. On the left side, name your travel brochure and sketch what you think a traveler might see. On the right side, describe the conditions the traveler might encounter and would need to prepare for. Include a description of the sights that are in store for a space traveler.

LESSON 1

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Lesson 1 | The Structure of the Solar System