Lesson 3 The Solar System - Iredell-Statesville · ESS.42 Differentiate among moons, asteroids,...

Lesson 3

How many planets do you see? Mars, Saturn, and Venus are in a triangle above the center stone. Mercury is below them to the left. Jupiter is much higher to the right. How far away are these planets from Earth?

The Solar System

Stonehenge, England

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434ENGAGE

ESS.42 Differentiate among moons, asteroids, comets, meteoroids, meteors, and meteorites (ESS-M-C2) ESS.43 Describe the characteristics of the inner and outer planets (ESS-M-C2) ESS.45 Identify Earth’s position in the solar system (ESS-M-C5)

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Distances of the Planets from the Sun

Planet Distance in AU

Mercury 0.4

Venus 0.7

Earth 1

Mars 1.5

Jupiter 5.2

Saturn 9.5

Uranus 19.2

Neptune 30

How far apart are the planets?

PurposeMake a model that shows the distances between the planets using astronomical units (AU), where one AU equals the average distance between Earth and the Sun. This distance is about 149,591,000 km (92,960,000 mi) .

Procedure

Let the length of each paper towel equal 1 AU. Using the information on the chart, roll out the number of paper towels you need to show the distance from the Sun to Neptune.

Make a Model Mark the location of the Sun at one end. Measure the distance that each planet would be from the Sun and draw the planet on the paper towel.

Draw Conclusions

Interpret Data Compare the distances between Mercury and Mars, Mars and Jupiter, and Jupiter and Neptune. Which are farthest apart?

Infer What can you conclude about the distances between the planets in the solar system?

Explore More

Your model has all of the planets in a line. How could you make a model to show the positions of the planets at a specific time? Write instructions that others can follow to make the model.

Step

• paper towels

• markers

• ruler

• masking tape

Step

Materials

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435EXPLORE

SI.12 Use data and information gathered to develop an explanation of experimental results (SI-M-A4) SI.14 Develop models to illustrate or explain conclusions reached through investigation (SI-M-A5)Also covers SI.15


What is the solar system?In ancient times, observers noticed that the

stars stayed the same distance from one another as they moved across the night sky. However, they noticed a few exceptions. Five of the tiny bright lights appeared in different parts of the sky every night. They did not stay the same distance from the other stars. At other times they were not present at all. The ancient Greek observers named these objects planets, a word that means “wanderer.” A planet is a large object that orbits a star.

Many ancient observers believed that Earth was the center of everything. They believed the Sun and all the objects in the night sky revolved around Earth in perfect circles. However, many astronomers doubted this belief because the planets moved in different ways.

In the early 1500s, the mathematician and astronomer Nicolaus Copernicus argued that Earth rotated on its axis and revolved around the Sun. His view changed how later astronomers understood the stars and planets.

Earth is one of eight planets in our solar system. A solar system is a star and the objects that orbit it. The eight planets in our solar system revolve around the Sun in elliptical orbits. Their order from nearest to farthest from the Sun is Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune.

Quick Check

Infer If scientists discovered a large object

moving around a distant star, what would they

call it?

Critical Thinking Is a moon that is larger than

many of the planets in a solar system also a

planet? Explain your answer. ▲ Earth is the third planet from the Sun.

▶ Essential Question What are the components of our solar system?

▶ Vocabularyplanet, p. 436

solar system, p. 436

inner planet, p. 438

outer planet, p. 440

comet, p. 442

asteroid, p. 443

meteor, p. 443

moon, p. 444

▶ Reading Skill Infer

Clues What IKnow

What IInfer

▶ Technology e-Glossary and e-Review online at www.macmillanmh.com

ESS.42, ESS.43, ESS.45

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436EXPLAIN


Uranus

Jupiter

Mars

Venus

Mercury

Sun

Neptune

Planet Name

Radius at the Equator

(km)

Mean Surface Temperature

(°C)

Surface Materials

Rings

Mercury 2,440 179 rocks no

Venus 6,052 482 rocks no

Earth 6,378 15 rocks no

Mars 3,397 -63 rocks no

Jupiter 71,492 -121 gases yes

Saturn 60,268 -125 gases yes

Uranus 25,559 -193 gases yes

Neptune 24,746 -193 to -153 gases yes

Which planet has the warmest surface temperature?

Clue: Find the highest temperature in the mean surface temperature column.

Earth

Saturn

asteroid belt

Planetary Data

Read a Table

The Solar System

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437EXPLAIN


What are the inner planets?The inner planets are closer to the Sun than the asteroid belt.

These planets are Mercury, Venus, Earth, and Mars. Although each inner planet has unique features, the inner planets have common characteristics. For example, the inner planets all have surfaces made of rock. Because of these rocky surfaces, the inner planets are also called the terrestrial planets. The inner planets’ orbits are also spaced close together. These planets have few or no moons, and none of them have rings.

The sizes of Mercury, Venus, and Mars are shown compared to Earth.

Distance From the Sun: 58 million km (36 million mi)

Mass: 0.06 × Earth

Surface Gravity: 0.38 × Earth

Number of Moons: 0

Surface Characteristics: Mercury’s surface looks a lot like the Moon’s surface. It is heavily scarred with craters. These craters were formed when meteorites smashed into the planet’s surface.

Special Features: Mercury has no true atmosphere. Because Mercury does not have an atmosphere, daytime temperatures are extremely high and nighttime temperatures are extremely low.

Mercury Distance From the Sun: 108 million km (67 million mi)

Mass: 0.82 × Earth


Number of Moons: 0

Surface Characteristics: The surface of Venus shows evidence of violent volcanic activity in the past. Venus has shield and composite volcanoes similar to those found on Earth. Long rivers of lava have been seen on Venus.

Special Features: A day on Venus is longer than its year. Venus rotates once every 243 Earth days and revolves around the Sun in 225 Earth days. Venus also rotates in the direction opposite Earth’s rotation. Pressure at the surface of Venus is about 90 times the atmospheric pressure at Earth’s surface. This pressure is enough to crush a spacecraft.

Venus

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438EXPLAIN


Planet Sizes

Use Numbers Using a scale of 2,000 km = 1 cm , find the diameter of each planet in centimeters.

Make a Model Using a ruler and scissors, cut circles out of poster board to show the sizes of the planets. Then label each planet.

Arrange the planets in order from nearest to farthest from the Sun.

How do the sizes of the inner and outer planets compare? Which planet is about the same size as Earth?

SI.14, SI.15

Quick Check

Infer If you were on Venus, in what

direction would you see the Sun rise

and set? Explain.

Critical Thinking How are the

inner planets alike? How are they

different?


Mass: 1 × Earth

Number of Moons: 1

Surface Characteristics: There might once have been as many craters on Earth as there are on Mercury. However, erosion on Earth caused these craters to disappear.

Special Features: Earth is the largest inner planet. It is the only planet in the solar system known to support life as we know it. Earth’s atmosphere keeps it from getting too hot or too cold.

Earth

Distance From the Sun: 227.9 million km (141.6 million mi)

Mass: 0.11 × Earth


Number of Moons: 2

Surface Characteristics: Mars is known as the red planet because it has a reddish surface color.

Special Features: Mars’s axis is tilted 25°. This means it has seasons. Polar ice caps melt in summer and form in winter.

Mars

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439EXPLAIN


What are the outer planets?There are four planets beyond the asteroid belt. These planets

are known as the outer planets. The outer planets include Jupiter, Saturn, Uranus, and Neptune. Although they differ from each other, these planets have some similarities. The outer planets are made mostly of gas. They are sometimes called the gas planets. Each of the gas planets has a metallic core and a thick atmosphere. They are much larger than the inner planets. Their orbits are also much farther apart than the orbits of the inner planets. All the outer planets have rings and many moons. A day on an outer planet is very short; they spin rapidly on their axes.


Mass: 318 × Earth


Number of Moons: 60+

Atmosphere Characteristics: The Great Red Spot is a huge storm that has been blowing continuously for more than 400 years. Its winds can reach speeds of about 435 km/h (270 mph). The storm is large enough to hold several Earths. Scientists believe that a combination of sulfur and phosphorus in the atmosphere gives this storm its color.

Special Features: Jupiter is so large that 1,000 Earths could fit inside it. It also has more mass than all of the other planets combined. Jupiter rotates faster than any other planet. It takes only 9 hours and 56 minutes to rotate once on its axis.

Jupiter

Distance From the Sun: 1,427 million km (886.7 million mi)

Mass: 95 × Earth



Atmosphere Characteristics: Saturn’s atmosphere is similar to Jupiter’s. It is composed mostly of hydrogen and helium. Winds on Saturn move at about 1,800 km/h (1,100 mph) near the equator.

Special Features: Saturn is known for its large, bright rings. The rings are made of pieces of ice and rock.

Saturn

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440EXPLAIN


Quick Check

Infer If scientists discover a new

planet that appears to be the same

color as Uranus, what can you infer

about its atmosphere?

Critical Thinking Why might the

outer planets have so many more

moons than the inner planets?

Pluto was once known as the ninth planet. Pluto’s elongated orbit and small size are different from those of the other planets. Because of these differences, scientists debated whether Pluto should be classified as a planet. In August 2006, the International Astronomical Union officially reclassified Pluto as a dwarf planet. Other dwarf planets include Ceres and Eris. Ceres is found in the asteroid belt between Mars and Jupiter. Eris is slightly larger than Pluto and even farther from the Sun.

Dwarf Planets

Distance From the Sun: 2,870 million km (1,783 million mi)

Mass: 14.5 × Earth



Atmosphere Characteristics: The blue-green color of Uranus is due to methane in the planet’s upper atmosphere.

Special Features: Uranus is unusual because it looks as though it was knocked on its side. Its axis of rotation is tilted about 98° to its orbit. Scientists think that a collision with another object caused Uranus to tip on its side.

Uranus

Distance From the Sun: 4,500 million km (2,796 million mi)

Mass: 17.2 × Earth


Number of Moons: 13

Atmosphere Characteristics: Like Uranus, methane in its atmosphere gives Neptune its blue color. Neptune has the strongest winds of any planet. The winds were measured to blow at speeds up to 2,000 km/h (1,250 mph) in some areas. Many storms have been detected.

Special Features: Neptune has at least five rings, none of which are very bright. One of Neptune’s moons, Triton, is larger than Pluto.

Neptune

The sizes of Saturn, Uranus, and Neptune are shown compared to Jupiter.

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441EXPLAIN


What are asteroids,

comets, and meteors?Different types of small objects are

present in space. These objects include comets, asteroids, and meteors.

Comets

A comet is a mixture of frozen gases, ice, dust, and rock that moves in an elliptical orbit around the Sun. Comets are thought to be bits of material left over from the formation of the solar system about 4.6 billion years ago.

When a comet is farther away from the Sun, the gases and ice in the comet are frozen. As the comet moves toward the Sun, the core, or nucleus, of the comet warms up. Some of the ice and the dust in the core form a cloud, or coma, around the nucleus. Together, the nucleus and the coma make up the head of the comet.

Comets have tails of ice and gases.

As the comet gets closer to the Sun, heat from the Sun pushes some of the coma away from the comet. This material forms a glowing tail that may stretch millions of kilometers behind the head. Sometimes two tails will form. One tail is made of ice, and one is made of gases.

Heat energy moves out from the Sun in every direction. As a comet moves around the Sun, the head stays closest to the Sun and the tail trails out behind it. No matter where the comet is in its path around the Sun, the comet’s tail always points away from the Sun.

Comets orbit the Sun, but the amount of time it takes them to orbit the Sun varies. Halley’s Comet was the first comet whose return was predicted. The comet gets close to Earth about every 76 years, most recently in 1986. The next time Halley’s Comet will be near Earth is in 2061.

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442EXPLAIN


Asteroids

An asteroid (AS•tuh•royd) is a rock that revolves around the Sun. Most of the thousands of asteroids in the solar system are located between Mars and Jupiter in the asteroid belt. Many asteroids have irregular shapes and look like potatoes. Some asteroids are less than 2 km (1 mi) wide, while others can be up to 800 km (500 mi) wide!

Meteors

The solar system is full of other small objects. In space, these objects are called meteoroids. If an object crosses paths with Earth and enters Earth’s atmosphere, it is called a meteor. Most meteors burn up as they travel through Earth’s atmosphere. If a meteor does land on the ground, it is called a meteorite.

The Leonid meteor shower occurs every year in mid-November.

Ida is a heavily cratered, irregularly shaped asteroid.

Quick Check

Infer As scientists identify materials

in comets, what might they infer

about the materials that existed as

the solar system formed?

Critical Thinking Draw the location

of the tail and the head of a comet

as it moves around the Sun.

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443EXPLAIN


How do the moons

compare?A moon is a natural object that

orbits a planet. Different planets have different numbers and sizes of moons.

The inner planets have fewer moons than the outer planets. Mercury and Venus do not have moons. Earth has one moon, and Mars has two.

With more than 60 moons, Jupiter has the most moons of any planet in the solar system. Saturn has more than 45 moons. Astronomers have discovered at least 27 moons around Uranus and 13 moons orbiting Neptune. As astronomers observe the outer planets with better telescopes and with space probes, they continue to find more moons.

Deimos(Mars)

Ganymede(Jupiter)

Moon(Earth)

Phobos(Mars)

Moons are also called satellites (SA•tuh•lites). A satellite is an object in space that circles around another object. While moons are natural satellites, people also put objects into space that orbit Earth or other planets. These objects are called artificial satellites. They include weather and communications satellites as well as space probes that orbit planets to observe their surfaces.

The size of the moons in the solar system varies. Some of the moons are only a few kilometers wide. Jupiter’s Ganymede is the largest moon in the solar system. Ganymede is larger in diameter than Pluto and Mercury. Earth’s moon is also larger than Pluto and is visible without a telescope. Ganymede is the only other moon that can be seen without a telescope.

1 cm

1,000 km

SCALE

1 cm

10 km

SCALE

Various Moons of the Solar System

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444EXPLAIN


Craters are seen on both types of rock. This means that objects have been hitting Ganymede for at least 4 billion years. Unlike those on the Moon, craters on Ganymede are flat. This may be because flowing ice on Ganymede’s surface smooths out their edges.

Deimos, Mars’s smaller moon, is composed of carbon-rich rock and ice. Deimos’s surface has craters that have been partially filled in by loose rock.

Quick Check

Infer How are a moon and an

artificial satellite different?

Critical Thinking What happens

when objects in space collide

with Earth?

Forming Craters

Sometimes small objects in space collide with large objects. When this happens, the impact often forms a crater, or a bowl-shaped hole, on the larger object’s surface. Many moons have craters. Craters vary in size because the objects that hit a moon are different sizes and travel at different speeds.

On Earth’s moon, the impact of an object knocks the surface material away so the rock underneath is exposed. The surface material piles around the edges of the crater. This makes the Moon’s craters distinct and easy to see from Earth.

Ganymede’s surface is made of ice and rock. The dark rock is about 4 billion years old and the light-colored rock is somewhat younger.

How large are these moons?

Clue: Use the scales.

Hyperion(Saturn)

Mimas(Saturn)

Miranda(Uranus)

1 cm

100 km

SCALE

Read a Photo

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445EXPLAIN


What is Earth’s moon

like?The Moon has been a source

of wonder throughout history. As technology has progressed, people have wanted to learn more and more about the Moon. The greatest amount of information about the Moon has come from data gathered by the Apollo missions, which included six Moon landings between 1969 and 1972.

Several different features have been identified on the Moon. Even though the Moon and Earth are hit by space objects at about the same rate, the Moon has more craters. Earth’s protective atmosphere causes most of the incoming objects to burn up.

Maria (MAR•ee•uh) are large, dark, flat surfaces on the Moon. The singular form, mare (MAR•ay), means “sea” in Latin. The smoothness of the maria led people long ago to think that they might be seas of water. Today scientists think the maria formed when huge space objects collided with the Moon’s surface. These large areas of impact then filled in with lava. When the lava cooled, it gave the maria their smooth appearance and dark color.

Highlands on the Moon are light-colored regions near the lunar poles. They are higher in elevation compared to the maria. The surfaces of the highlands have more craters than the maria do, so scientists believe that the highlands are geologically older landforms.

Mountains on the Moon are found around the edges of large maria. The mountains probably formed from the same impacts that formed the maria. Mountain ranges on the Moon are named after mountain ranges on Earth.

Valleys on the Moon are cigar-shaped depressions. Perhaps the most famous is the Alpine Valley on the northeastern edge of Mare Imbrium. New evidence suggest that the floors of some deep Moon valleys may contain small amounts of ice.

This image shows craters on the Moon’s surface and a view of Earth in the background.

Mount Hadley Delta rises about 4,000 m (13, 124 ft).

Quick Check

Infer What probably caused

mountains to form around the edges

of the maria?

Critical Thinking Why do people

who go to the Moon need to wear

space suits?

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446EXPLAIN

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Think, Talk, and Write Vocabulary A mixture of frozen gases, ice, dust, and rock that orbits the Sun is a(n) .

Infer If you knew probes that traveled to Venus were crushed after a few hours, what could you infer about atmospheric pressure on Venus?

Clues What IKnow

What IInfer

Critical Thinking Earth is the only planet known to have life. What do you think makes this possible? What might prevent life from existing on other planets?

Test Prep Which is the largest planet in the solar system?A EarthB MarsC SaturnD Jupiter

Test Prep Which planet takes the longest time to orbit the Sun?A MercuryB VenusC JupiterD Uranus

Essential Question What are the components of our solar system?

Visual Summary

Make a Study GuideMake a three-tab book. Use the titles shown. On the inside of each tab, summarize what you have learned.

Science FictionRead The War of the Worlds by H.G.

Wells. Write a report about the novel.

Discuss how much of the story is based

on fact and how much is fiction.

Planet SurfacesResearch the surface features of one

of the inner planets. Then draw an

illustration of what the planet’s surface

might look like.

Writing Link Art Link

-Review Summaries and quizzes online at www.macmillanmh.com

The solar system is made of the Sun, the planets and their moons, asteroids, meteoroids, and comets.

The planets and moons in the solar system vary in size and surface material.

The Moon has a surface of different features, including craters, maria, and highlands.

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447EVALUATE


Step

Step

Step

Structured Inquiry

tape

dowels

construction paper

30-m tape measure

Procedure

Make a Model Make labels for each planet and the Sun. Attach each label to a dowel.

Place the marker labeled Sun at one end of a large open area.

Measure Use the table below to construct your model. Measure the scaled distance from the Sun to Mercury, and place the marker labeled Mercury in the ground.

Continue marking the distances of the planets from the Sun. Draw your model and record your observations about the solar system.

How can you model the solar system?

PurposeOur solar system consists of the Sun, planets, moons, and other bodies, including asteroids, comets, and meteoroids. Each planet has its own orbit around the Sun. What can a model of the solar system show you? Construct a model of the solar system and use it to compare the distances between planets.

PlanetDistance from Sun

(in kilometers)Distance from Sun, to Scale

(1 cm = 1,000,000 km)

Mercury 57,900,000 58 cm

Venus 108,200,000 1 m, 8 cm

Earth 149,600,000 1 m, 50 cm

Mars 227,900,000 2 m, 28 cm

Jupiter 778,400,000 7 m, 78 cm

Saturn 1,426,700,000 14 m, 27 cm

Uranus 2,871,000,000 28 m, 71 cm

Neptune 4,498,300,000 44 m, 98 cm

Materials

markers

448EXTEND

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Open Inquiry

Think of a question about the solar system to investigate. For example, are the planets always the same distance from the Sun, or do their distances change? Design a data-collection process or method of research to answer your question. Your data must be organized to test only one variable, or one item being changed.

Remember to follow the steps of the scientific process.

Draw Conclusions

Interpret Data According to your model, which planet is closest to the Sun? Which planet is closest to Earth?

Interpret Data How does the distance from the Sun to Jupiter compare to the distance from Jupiter to Saturn? How does the distance from the Sun to Saturn compare to the distance from Saturn to Uranus?

Guided Inquiry

Could you model the

solar system, including

the planets’ sizes and the

distances between the

planets?

Form a HypothesisWhy is it so difficult to make a true scale model of the solar system? Write your answer in the form “If I try to model the sizes of the Sun and all the planets accurately, then...”

Test Your HypothesisDecide what data you need to collect to make your model. Then choose a scale to use for your model, and calculate the sizes and positions of your model Sun and planets.

Draw ConclusionsHow easy would it be to make your model? Explain.

Ask a Question

Form a Hypothesis

Test Your Hypothesis

Draw Conclusions

449EXTEND

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SI.33 Evaluate models, identify problems in design, and make recommendations for improvement (SI-M-B4) SI.38 Explain that, through the use of scientific processes and knowledge, people can solve problems, make decisions, and form new ideas (SI-M-B6)Also covers SI.14, SI.15

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Lesson 3 The Solar System - Iredell-Statesville · ESS.42 Differentiate among moons, asteroids,...

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