lesson 1 the sun and other starsnewlondonscs.sharpschool.com/userfiles/servers/server... · and the...

Lesson 1

The Sun and Other Stars

On January 20, 2005, satellites that carried cell phone and cable signals suddenly shut down. They had been struck by a burst of energy. Where did this energy come from?

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Template First Pass Second Pass Confi rming Pass PDF Proof

410ENGAGE

ESS.39 Identify the physical characteristics of the Sun (ESS-M-C1) ESS.40 Describe the significance of Polaris as the North Star (ESS-M-C1)

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How does the Sun’s diameter compare with that of Jupiter, the largest planet? Do research to answer this question and make a model to represent the difference in their sizes.

Explore More

Diameter

The Sun 1,390,000 kilometers

Earth 12,760 kilometers

Step

How do the sizes of Earth

and the Sun compare?

PurposeStudy the size difference between Earth and the Sun.

Procedure

Use Numbers What proportion is the size of Earth to the size of the Sun?

Use Numbers What would the diameter of the Sun be if the diameter of Earth was 0.5 cm?

Make a Model Use appropriate tools to design a model of Earth and the Sun to this scale.

How many Earths would it take to cover the length of the model of the Sun’s diameter?

Draw Conclusions

Communicate Does this model show an accurate comparison between the diameters of the Sun and Earth? Why or why not?

• meter stick

• ruler

• colored pencils

• clear tape

Step

Materials

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411EXPLORE

SI.14 Develop models to illustrate or explain conclusions reached through investigation (SI-M-A5) SI.15 Identify and explain the limitations of models used to represent the natural world (SI-M-A5)Also covers SI.3

at


Earth and the Sun are shown here on a scale of 1 centimeter = 50,000 kilometers. At this size, Earth and the Sun are 2,992 cm (about 98 feet) apart.

Earth

Sun

▶ Essential QuestionWhat are the characteristics of the Sun and other stars ?

▶ Vocabularystar, p. 413

astronomical unit, p. 413

solar flares, p. 415

constellation, p. 416

▶ Reading Skill Draw Conclusions

Text Clues Conclusions

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

ESS.39, ESS.40

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412EXPLAIN


What is the Sun?The Sun is a star. A star is an

object that produces thermal and light energy. The Sun is at the center of the solar system. The solar system includes all the planets and other objects that orbit the Sun.

The stars that produce the most energy make about 10 million times more energy than the Sun. The least-productive stars make only one-hundredth as much energy as the Sun.

The Sun is an average-sized star and the largest object in the solar system. The Sun’s diameter is about 1,390,000 kilometers (863,706 miles). If the Sun were a hollow ball, more than 1 million Earths could fit inside it. The Sun looks larger than the other stars that can be seen in the night sky because it is much closer to Earth.

The mean, or average, distance between the Sun and Earth is 149,591,000 km (92,960,000 mi). To scientists, this distance is known as one astronomical unit (as•truh•NAH•mi•kulh), or AU. The next-closest stars are found in the Alpha Centauri star system. They are about 271,931 AUs away .

Finding the Sun’s Mass

It is impossible to measure the weight of the Sun. After all, the Sun cannot be put on a scale.

However, it is possible to measure the mass of the Sun. Recall that mass is the amount of matter in an object. The mass of the Sun can be calculated if you know two facts. The first fact is the length of time it takes for a planet to make one trip around the Sun (for Earth, that is 365.24 days). The second fact is the distance between the planet and the Sun (for Earth, that is 149,591,000 km ).

Using this information, scientists have calculated the Sun’s mass to be 2 million trillion trillion kilograms. That’s 2,000,000,000,000,000,000,000,000,000,000 kg ! This is 745 times greater than the mass of all the other objects in the solar system put together. As a matter of fact, the mass of the Sun makes up 99.8 percent of all the mass in the solar system.

Quick Check

Draw Conclusions Why are the

planets not stars?

Critical Thinking Why are

astronomical units used to measure

distances rather than kilometers?

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413EXPLAIN


What are the parts

of the Sun?The Sun is a huge sphere made up

mostly of two very light gases, hydrogen and helium. Hydrogen makes up about 71 percent of the Sun’s mass. Another 27 percent is made up of helium. Oxygen, carbon, and other gases make up the remaining 2 percent of the Sun’s mass.

Most of the energy that the Sun produces is formed in its core. At its core, the Sun has a temperature of 10 million to 20 million degrees Celsius (18 million to 36 million degrees Fahrenheit) . The pressure is more than 1 billion times greater than the air pressure at sea level on Earth.

The radiation layer, which is next to the core, moves the energy produced in the core in every direction. It can take millions of years for energy to move out of this layer.

In the convection layer, gases with different energies move in circles in a way similar to air with different densities. Energy moves out of this layer in about a week.

The photosphere is the visible surface of the Sun. It is not a solid surface, but rather a layer of gases. The photosphere is cooler than the core. Its temperature is about 5,730°C (10,346°F).

The next layer of the Sun is the chromosphere, or the inner layer of the Sun’s atmosphere. When it can be seen, it looks like a red circle around the Sun.

The corona is the outermost layer of the Sun’s atmosphere. The corona takes on different shapes around the Sun depending on changes in the temperature of the photosphere.

radiation layer

core

convection layer

photosphere

corona

chromosphere

Layers of the Sun

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414EXPLAIN


Solar Flares

Solar flares are occasional eruptions of energy from the Sun’s surface that stretch far out into space. Sometimes this energy disrupts satellites, interfering with TV, radio, and cell phone communication systems.

Energy from solar flares also causes displays of different-colored lights in Earth’s upper atmosphere. These lights are called the aurora borealis

(uh•RAW•uh bawr•ee•AL•is), or northern lights, in the Northern Hemisphere. Seen frequently in Alaska and Canada, they are seen in the southern United States after large solar flare eruptions.

Solar flares are often associated with sunspots. Sunspots, or dark spots on the Sun, are relatively small regions of the photosphere that have a lower temperature than the surrounding regions.

The Parts of the Sun

Make a Model Use modeling clay to make a model of the Sun that includes all of the layers.

Be Careful. Using a plastic knife, cut away a quarter of your Sun so you can see into it.

Add sunspots and solar flares to the surface of your Sun.

Communicate Write a description of your Sun. Include a color key to identify the layers.

SI.14, SI.15

Quick Check

Draw Conclusions Why does it

take millions of years for energy that

moves in every direction to leave the

radiation layer?

Critical Thinking Why is it harmful

to our eyes to look directly at the

Sun?

What is the layer of the Sun between the core and the convection layer called?

Clue: Find the labels on the diagram for the core and for the convection layer, and look for the name of the layer between them.

sunspot

solar flare

Read a Diagram

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415EXPLAIN


What are constellations?The Sun is just one of billions and billions of stars in the

universe. Scientists use constellations to map all the stars. A constellation is a pattern in the night sky formed by a group of stars. Constellations were used by ancient cultures as seasonal calendars and for navigation. Native American, Greek, and Roman cultures name many star patterns after animals, characters from stories, or familiar objects.

Some constellations, like the Big Dipper and Little Dipper, are used by modern travelers. These two constellations point to Polaris, the North Star. If you travel in the direction of Polaris, you will be moving north. If you ever become lost, look for Polaris. It will always be directly north of your location.

How can you use the Big Dipper to help you find Polaris?

Clue: Look at the stars in the bowl of the Big Dipper.

Read a Diagram

Finding Polaris

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416EXPLAIN


Sirius

Greek constellations

Modern Constellations

Today, astronomers divide the sky into 88 zones. Each zone includes a constellation. Many of these 88 constellations are the ancient Greek and Roman constellations. More recently, astronomers gave names to constellations visible in the Southern Hemisphere. New constellations were needed because observers in ancient Greece and Rome could not see any stars below the southern horizon. The stars you see depend on your location.

How can you find certain stars in the night sky? The easiest way is by looking for the constellation in which it is located. Rigel, for example, is a star in the constellation Orion. Find Orion, and you will locate Rigel.

Quick Check

Draw Conclusions Why did

ancient cultures group stars into

constellations?

Critical Thinking How can a

scientist tell other scientists where a

newly discovered star is located?

Observing Constellations

Observe On a clear night, go outside after dark and observe the stars. Be sure to take an adult with you.

Choose a section of the night sky, and draw the stars you see. Find patterns in the stars that look like something familiar to you. In your science learning log, draw what you think each star pattern resembles.

Create names for your star pattern. Also in your science learning log, write stories describing the characters or objects your star patterns represent.

Communicate Share your drawings and stories with your classmates. Do any of your constellations match those observed by other students?

SI.19the constellation Canis Major

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417EXPLAIN


Some stars are brighter than others. Stars appear less bright the farther they are from Earth. For example, Sirius (SEER•ee•us) looks brighter to us than Rigel does. However, Rigel is actually a much brighter star than Sirius is. Can you guess which star is closer to Earth? Sirius is much closer to Earth than Rigel. Think of two flashlights, one much brighter than the other. If you placed them side by side, the difference in brightness would be easy to see. However, if you moved the brighter flashlight much farther from you, it would seem dimmer. The brightness of a star is called its magnitude. A star’s actual brightness is called its absolute magnitude. How bright a star looks in Earth’s night sky is its apparent magnitude. Apparent magnitude depends on how much light a star gives off and how far away it is from Earth.

Another property of stars is color.A star’s color tells you about its surface temperature. Think about the coils inside a toaster. As the coils heat up, they turn red, then orange, and then orange-yellow. Red and orange colors indicate cooler stars. Yellow indicates hotter stars, and blue-white indicates the hottest stars.

Stars also differ in size. Our Sun is an average-sized star. Red supergiants are the largest stars and white dwarfs are among the smallest.

Quick Check

Draw Conclusions Why does the

Sun look larger and brighter than

any other star?

Critical Thinking If one star

appears brighter than another, can

you correctly assume it is closer?

Stars come in widely varying sizes. A white dwarf can be as small as Earth.

What are some properties of stars?

Star Sizes

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418EXPLAIN


Think, Talk, and Write Vocabulary An object that produces thermal and light energy is a(n) .

Draw Conclusions What might result from a number of large solar flares?

Text Clues Conclusions

Critical Thinking How would Earth be affected if the Sun stopped producing thermal and light energy?

Test Prep The Sun is made up of all of the following materials except which?

A hydrogen B heliumC carbonD steam

Test Prep What would you look for in order to locate Polaris, the North Star?

A sunspots B planetsC solar flaresD constellations

Essential Question What are the characteristics of the Sun and other stars?

Visual Summary

T he Sun is a star and the largest object in the solar system.

Parts of the Su n include the photosphere, chromosphere, and corona. Solar flares occasionally occur.

Polaris is the North Star. It can help you find your way if you are lost.

Make a Study GuideMake a trifold book. Use the titles shown. Then summarize what you have learned.

Helpful or HarmfulIs the Sun helpful or harmful? Write

about some of the things that you can

do because of the Sun’s energy. Write

about ways the Sun can be harmful to

you. Be sure to include safety tips.

Compare TemperaturesThe average temperature of the surface

of Earth is 14°C . The surface of the Sun

is 400 times hotter. What is the average

temperature of the surface of the Sun?

Writing Link Math Link M.8

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

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419EVALUATE

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the constellation Cygnus

spring summer

Inquiry Skill: ObserveThe location of an observer determines which

constellations he or she can observe. Some constellations can only be seen in certain seasons. For example, the constellation Cygnus, the swan, is only visible in the Northern Hemisphere in the summer. What constellations can be observed in each of the seasons?

▶ Learn ItWhen you observe, you use one or more of

your senses to learn about the world around you. It is important to record what you observe and any measurements you take. Scientists record their observations so they can share information with others. You may also want to organize your observations in a chart or a graph. Then you can see your information at a glance.

The illustrations on these two pages show the same view of the night sky as seen in different seasons. In this activity you will use these images to identify different seasonal star patterns.

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420EXTEND

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fall winter

Make a list of the constellations you observe.

Compare your list of constellations with those of your classmates. Did your classmates see the same constellations?

Use reference materials to see which constellations are visible in the Louisiana night sky during the current season. Does your list of constellations contain all the constellations on the list you researched? Was your list missing any constellations? See if you can find the constellations you missed on another night. Why can you only see some constellations during certain parts of the year?

▶ Try ItMaterials paper, pencil, star chart,

reference materials

Create a table that lists the seasons (spring, summer, fall, and winter) in four separate columns.

Using a star chart and other reference materials, identify the different seasonal star patterns that you see in each illustration.

On your table, record the names of the constellations that you have identified under the appropriate season.

▶ Apply It Continue to use your observation skills. See if you can identify star patterns in the Louisiana night sky. Go outside with an adult and observe the stars. Try to identify as many constellations as you can. You may want to use a local star chart and other reference materials as a guide.

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421EXTEND

ESS.41 Explain why the Moon, Sun, and stars appear to move from east to west across the sky (ESS-M-C1) SI.3 Use a variety of sources to answer questions (SI-M-A1) SI.7 Record observations using methods that complement investigations (e.g., journals, tables, charts) (SI-M-A3)

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