* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Planets, Moons, and Stars
International Ultraviolet Explorer wikipedia , lookup
Outer space wikipedia , lookup
Corvus (constellation) wikipedia , lookup
IAU definition of planet wikipedia , lookup
Tropical year wikipedia , lookup
Aquarius (constellation) wikipedia , lookup
History of astronomy wikipedia , lookup
Astronomy on Mars wikipedia , lookup
Definition of planet wikipedia , lookup
Astrobiology wikipedia , lookup
Planets in astrology wikipedia , lookup
Astronomical unit wikipedia , lookup
Lunar theory wikipedia , lookup
Planetary habitability wikipedia , lookup
Rare Earth hypothesis wikipedia , lookup
History of Solar System formation and evolution hypotheses wikipedia , lookup
Formation and evolution of the Solar System wikipedia , lookup
Late Heavy Bombardment wikipedia , lookup
Geocentric model wikipedia , lookup
Satellite system (astronomy) wikipedia , lookup
Comparative planetary science wikipedia , lookup
Extraterrestrial life wikipedia , lookup
Hebrew astronomy wikipedia , lookup
Dialogue Concerning the Two Chief World Systems wikipedia , lookup
CHAPTER 8 Planets, Moons, and Stars Lesson 1 The Sun and Earth . . 316 Lesson 2 The Moon and Earth . . . . . . . . . . 326 Lesson 3 The Planets . . . . . . . . 336 Lesson 4 The Stars . . . . . . . . . . 346 What objects move through space, and how do they move? 314 Saturn and one of its moons, Tethys Key Vocabulary rotate to spin (p. 318) More Vocabulary axis, p. 319 orbit, p. 320 star, p. 322 crater, p. 332 telescope, p. 342 revolve to move around another object (p. 320) space probe, p. 342 phase each shape of the Moon we see (p. 328) solar system a system made up of a star and the objects that move around it (p. 338) planet a large body of rock or gas with a nearly round shape that revolves around a star (p. 338) constellation a group of stars that seem to form a picture (p. 349) 315 Lesson 1 The Sun and Earth The Sun seems to rise from behind this tree. The tree blocks the Sun’s light and forms a long shadow. How do shadows change during the day? 316 ENGAGE How do shadows change throughout the day? Materials Form a Hypothesis chalk How does the Sun’s location affect the length of shadows cast on the ground? How does it affect their position? Write a hypothesis. Test Your Hypothesis Work in pairs outside on a sunny morning. Use chalk to mark an X on the pavement. Have your partner stand on the X. Trace your partner’s shadow. measuring tape Step Measure Use a measuring tape to find the length of the shadow. Observe the location of the Sun and the shadow. Record the data in a table. Be Careful. Never look directly at the Sun. Observe Repeat steps 2 and 3 at midday and in the afternoon. How did the Sun’s location and the shadow change? Draw Conclusions Interpret Data When was the shadow shortest? When was the shadow longest? How did the Sun’s position change? Step Time Infer What caused the shadow to change position and length? Explore More Experiment How can you find out in which month the Sun’s position appears highest in the sky? Lowest? Length and Location Location of of Sun Shadow Morning Midday Afternoon 317 EXPLORE Why is there day and night? Main Idea Earth rotates and revolves around the Sun. Earth’s movement causes day and night and the seasons. Vocabulary rotate, p. 318 axis, p. 319 revolve, p. 320 orbit, p. 320 star, p. 322 -Glossary at www.macmillanmh.com As you read this page, you are moving through space. All the other things on Earth are moving, too. Earth rotates (ROH•tayts), or spins, like a giant top in space. As Earth rotates, we see the Sun in a different place in the sky. At sunrise, the Sun is low in the eastern sky. The Sun’s light casts long shadows. At midday, the Sun is high in the sky. Shadows are short then. At sunset, the Sun is low in the western sky and shadows are long again. The Sun seems to move in the sky, but it does not. Earth does all the moving! The Sun’s Position in the Sky sunrise Reading Skill Sequence east west midday Technology Explore day and night with the Secret Agents. east The Sun seems to rise in the east and set in the west. Looking at these pictures, you are facing south. 318 EXPLAIN west sunset east west Day and Night axis Sun rotating Earth As Earth rotates on its imaginary axis, we have day and night. Earth’s rotation causes day and night. As Earth rotates, one side of Earth faces the Sun. This side has daytime. At the same time, the other side of Earth faces away from the Sun. This side has nighttime. Earth keeps spinning. Day becomes night for one side of Earth. Night becomes day for the other side of Earth. This happens over and over again. It takes 24 hours for Earth to make one complete turn on its axis (AK•sis). An axis is a line through the center of a spinning object. One complete turn is one day. We think of a day as daytime hours. However, a day is made up of daytime and nighttime. Model Earth’s Rotation Make a Model Carefully push a pencil through a foam ball. The ball represents Earth. The pencil represents Earth’s axis. Press a paper clip into the side of the ball. The paper clip represents you. Observe Shine a light on the paper clip. The light represents the Sun. On the model, where is it day? Observe Rotate the pencil so the paper clip faces away from the light. Where is it night? Interpret Data What does this model help to show? Quick Check Sequence How does the Sun appear to move across the sky? Critical Thinking What might happen if Earth did not rotate? 319 EXPLAIN Why are there seasons? Earth rotates on its axis. It also revolves (ri•VOLVZ) around the Sun. To revolve means to move around another object. Earth revolves around the Sun in a regular path called an orbit (AWR•bit). It takes Earth about 365 days to make one trip around the Sun. We call this one year. Seasons change as Earth revolves because of Earth’s tilted axis. Earth’s axis is not straight up and down compared with its orbit. For part of Earth’s orbit, the Northern Hemisphere, or upper half of Earth, is tilted toward the Sun. The Northern Hemisphere has summer. At the same time, the Southern Hemisphere, or lower half of Earth, is tilted away from the Sun. The Southern Hemisphere has winter. Seasons in the Northern Hemisphere spring Northern Hemisphere summer Southern Hemisphere 320 EXPLAIN winter fall At other times, the Northern Hemisphere is tilted away from the Sun and has winter. At the same time, the Southern Hemisphere is tilted toward the Sun and has summer. The diagram can help you see this. The Northern Hemisphere gets the most light and heat from the Sun in summer. Days are longer. Temperatures are warmer than in any other season. As Earth continues its orbit, the days get shorter and cooler. Fall begins. summer fall The Northern Hemisphere gets the least light and heat from the Sun in winter. Days are shorter. Temperatures are cooler than in any other season. As Earth continues its orbit, the days get longer and warmer. Spring begins. winter Read a Diagram What is the same about Earth’s axis as it moves around the Sun? Clue: Compare the drawings of Earth’s axis for each of the four seasons. spring Watch how seasons change at www.macmillanmh.com Quick Check Sequence Which season comes before fall? Critical Thinking How would seasons change if Earth moved more slowly around the Sun? Like many living things, this tree changes through the seasons. 321 EXPLAIN What is the Sun like? The Sun is a star. A star is a ball of hot, glowing gases. The temperature inside the Sun is about 59 million degrees Fahrenheit (15 million degrees Celsius). This is hot enough to melt Earth! The Sun is about 150 million kilometers (93 million miles) away from Earth. If you could travel there by car on a highway, it would take more than 160 years. Even though the Sun is that far away, it provides Earth with light and heat. Life on Earth could not exist without the Sun. Plants could not grow. Earth would freeze. The Sun sometimes has violent, fiery explosions that fly off into space. They are called solar flares. Quick Check Sequence What would happen to Earth if the Sun’s light were blocked for many years? Critical Thinking Do you think that people could travel to the Sun? Explain your answer. 322 EXPLAIN It would take 109 Earths to fit across the Sun. Visual Summary Earth rotates on its axis. This causes day and night. Think, Talk, and Write Main Idea What causes day and night? Vocabulary What is a star? Give an example. Seasons change because Earth revolves around the Sun and is tilted on its axis. Sequence How do seasons change in the Northern Hemisphere? The Sun is a star that supplies Earth with light and heat. Critical Thinking How would the seasons be different if Earth were not tilted on its axis? Make a Study Guide Test Prep Why are there seasons? Make a Trifold Book. Use it to summarize what you learned about the Sun and Earth. Math Link Use a Calendar Use a calendar to find out when the next season begins. What is the date? How many days from now is that? Choose the BEST answer. A Earth rotates on its axis and revolves around the Sun. B Earth has a tilted axis and revolves around the Sun. C The Sun revolves around Earth. D Earth’s distance from the Sun changes. Health Link Sun Safety Find out how sunlight can benefit human health. How can it be harmful to human health? How can people avoid the harmful effects of sunlight? Write a report. -Review Summaries and quizzes online at www.macmillanmh.com 323 EVALUATE Seasons Where You Live You have learned about seasons. Now think about what the seasons are like in your state. Do seasons have different kinds of weather? Does it snow in the winter? How hot is it in the summer? Think about the things you do during different seasons. Personal Narrative A good personal narrative tells a story from the writer’s personal experience expresses the writer’s feelings tells events in an order that makes sense Write About It Personal Narrative Choose a season. Tell a true story about something you did during that season. Explain why you still remember the event. How did it make you feel? Describe what the weather was like. -Journal Write about it online at www.macmillanmh.com 324 EXTEND Converting Hours to Minutes Daytime is longer in summer than it is in winter. Look at the table below. It shows the number of daylight hours for summer and winter in Boston, Massachusetts. Longest and Shortest Day in Boston Date Approximate Hours of Daylight June 21 15 December 21 10 Convert Hours Multiply the number of hours by the number of minutes there are in one hour. There are 60 minutes (min) in one hour (h). Example: 5 h x 60 min/h = 300 min Solve It How long is Boston’s longest day in minutes? How long is the shortest day in minutes? What is the difference in minutes between the longest day and the shortest day? 325 EXTEND Lesson 2 The Moon and Earth St. Louis, Missouri The Moon does not look the same today as it did yesterday. How will it look in one week? Does the Moon’s shape really change? 326 ENGAGE How does the Moon’s shape seem to change? Make a Prediction Step How will the Moon seem to change during one school week? Write a prediction. Test Your Prediction Observe Work with an adult. Look at the Moon each night for one school week. You can also use the Internet to find out what the Moon looks like each night. Communicate Record what the Moon looks like each night. Also record where the Moon is in the sky and the time that you observed it. Draw Conclusions Interpret Data How did the Moon’s shape seem to change each night? How does its location seem to change? Predict What will the Moon’s shape look like for the next few nights? Step Day Monday Explore More Tuesday Experiment How does the Moon’s shape Wednesday and position in the sky seem to change over several months? Make a plan to find out. Observation Thursday Friday 327 EXPLORE What are the phases of the Moon? Main Idea On many nights you can see the Moon. The Moon is a sphere, or ball, of rock. It is Earth’s closest neighbor in space. The Moon is a satellite of Earth. A satellite is anything that revolves around another larger object in space. The Moon revolves around Earth, much like Earth revolves around the Sun. The Moon’s shape and position in the sky seem to change. Vocabulary phase, p. 328 crater, p. 332 -Glossary at www.macmillanmh.com Reading Skill Cause and Effect Technology Each day the Moon seems to change shape. Sometimes you can only see a small part of the Moon. At other times the Moon is a big, bright circle. Still other times you cannot see the Moon at all. Each shape of the Moon we see is called a phase (FAYZ). The photos below show the eight main phases of the Moon. Have you seen the Moon in each of these phases? Moon Phases Explore Planet Earth with the Secret Agents. new Moon 328 EXPLAIN crescent Moon first-quarter Moon gibbous Moon Like the Sun, the Moon seems to rise, move across the sky, and set each day. This happens because of Earth’s rotation. As Earth rotates on its axis, the Moon’s position in the sky moves from east to west. The Moon seems to glow in the night sky. However, the Moon does not make its own light. The Moon appears to shine because sunlight reflects, or bounces, off the Moon. Quick Check Cause and Effect Why does the Moon seem to rise and set each day? Critical Thinking How could Sometimes we can see the Moon during the daytime. you predict what the shape of the Moon will be next week? full Moon gibbous Moon last-quarter Moon crescent Moon 329 EXPLAIN The Moon’s Orbit sunlight You see the last-quarter Moon about 21 days after the new Moon. A new Moon occurs about every 29_21 days. You see the first-quarter Moon about 7 days after the new Moon. You see the full Moon about 14 days after the new Moon. Read a Diagram When can you see a full Moon? The photos show what the first-quarter Moon, full Moon, and last-quarter Moon look like from Earth. 330 EXPLAIN Clue: Look at the diagram and read the captions. Why does the Moon’s shape seem to change? The Moon may seem to change shape, but it is always a sphere. It only appears to change shape because you see different amounts of its lighted side. The Sun shines on and lights half of the Moon’s surface. The other half faces away from the Sun. It is in darkness. As the Moon revolves around Earth, different amounts of the Moon’s lighted half face Earth. The lighted parts are the phases you see. When the Moon is between Earth and the Sun, there is a new Moon. You cannot see the Moon at all. The Moon’s lighted side faces away from Earth. As the Moon continues to revolve, you see more and more of the Moon’s lighted side. When you see the entire lighted half, there is a full Moon. As the Moon continues to revolve, you begin to see less and less of the lighted side. This cycle happens about every 291_2 days. Make a Flip Book Draw what a Moon phase looks like on the right side of an index card. Label the phase. Do this for each of the eight phases. Put the cards in order. Staple them together on the left side. Flip the pages with your thumb. How does the Moon’s shape seem to change? Quick Check Cause and Effect What causes the Moon’s phases to change? Critical Thinking What would the Moon look like if it did not revolve around Earth? 331 EXPLAIN What is it like on the Moon? Both the Moon and Earth are spheres. They both rotate. They both revolve. They both get light from the Sun. They are both made of rock. In other ways, though, they are very different. Earth is about four times larger than the Moon. Unlike Earth, the Moon has no atmosphere. It has no liquid water. There are no living things on the Moon. Craters of all sizes are found on the Moon’s surface. The Moon’s surface is also different from Earth’s. Most of its surface is covered with craters (KRAY•tuhrz). A crater is a hollow area, or pit, in the ground. Craters formed on the Moon when chunks of rock from space crashed into the Moon. Quick Check Cause and Effect What caused craters to form on the Moon? Critical Thinking Why are there This is what Earth looks like from the Moon. 332 EXPLAIN no living things on the Moon? The Moon’s temperatures are colder and warmer than Earth’s. Visual Summary Think, Talk, and Write The Moon seems to change shape each night. These shapes are called phases. Main Idea Why does the Moon The Moon revolves around Earth. This causes the different phases of the Moon. Cause and Effect What causes seem to change shape? Vocabulary What is a crater? the Moon to rise and set? In many ways, the Moon and Earth are different. Critical Thinking Why can you not see the new Moon phase? Test Prep How are Earth and the Make a Study Guide Moon similar? A Both have an atmosphere. B Both make their own light. C Both have living things. D Both are spheres. Make a Trifold Book. Use it to summarize what you learned about the Moon and Earth. Math Link Solve a Problem Objects weigh about six times more on Earth than they would on the Moon. If a Moon rock weighs 9 pounds on the Moon, about what would it weigh on Earth? Social Studies Link Do Research Some astronauts have actually walked on the Moon. Do research to find out about one of these astronauts. Share your findings with the class. -Review Summaries and quizzes online at www.macmillanmh.com 333 EVALUATE Materials Structured Inquiry Why does the Moon’s shape appear to change? Form a Hypothesis lamp The Moon completes one orbit around Earth about every 29 _21 days. How does the Moon’s position in space affect how we see the Moon? When do we see a full Moon? When do we see a last-quarter Moon? Write a hypothesis. ball Step Test Your Hypothesis Make a Model Hold the ball and stretch out your arm in front of you. Position your arm so that the ball is a little higher than your head. The ball is the Moon, and your head is Earth. Observe Your teacher will turn on a lamp. The lamp represents the Sun. Turn your back to the light so that the light shines on the ball. What part is lit up? Experiment Turn in place while holding the ball. Keep the ball in front of you. Notice the change in light and shadow on the ball. Communicate Record your observations by drawing or describing what you saw as you turned. Repeat the experiment several times. Are your observations the same with each trial? 334 EXTEND Draw Conclusions Observe Where is the ball when it is lit up like a full Moon? Where is the ball when it looks like a last-quarter Moon? Infer Why does the Moon’s shape appear to change? How do you know? Guided Inquiry How does the Moon’s position change? Form a Hypothesis Open Inquiry What other questions do you have about the Moon? Talk with your classmates about questions you have. How might you find the answers to your questions? How does the Moon’s position change in the night sky over the course of one month? Write a hypothesis. Test Your Hypothesis Design a plan to test your hypothesis. Remember your plan should test only one variable—the Moon’s position in the sky. Decide on the materials you will need. Then write the steps you plan to follow. Remember to follow the steps of the scientific process. Ask a Question Form a Hypothesis Draw Conclusions Did your results support your hypothesis? Why or why not? Share your results with your classmates. Test Your Hypothesis Draw Conclusions 335 EXTEND Lesson 3 The Planets What is that bright point of light near the Moon in this photo? It is not a star. It is the planet Venus! What are planets? How do they move through space? 336 ENGAGE How do the planets move through space? Materials Purpose Model how the positions of the planets change. masking tape Procedure Work in a large room or other area. Put a chair in the center of the room. Tape the card labeled Sun to the chair. Tape a line from the chair to a wall. Form two groups. Each student in the first group will take a card and line up along the tape in order: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune. 8 planet cards and 1 Sun card Step Make a Model Students in the first group model how the planets move by walking in a circle around the Sun. Take steps of the same size. Count steps together. Stop counting when you reach the tape again. Students in the second group repeat steps 2–3. Use Numbers Do all the “planets” complete one trip around the Sun in the same number of steps? Step Draw Conclusions What was different about the orbits? Infer How do planets move through space? Explore More Predict What planets can you see in the night sky where you live? Make a plan to find out. 337 EXPLORE What is our solar system? Main Idea Earth is one of eight planets that revolve around the Sun. Vocabulary solar system, p. 338 planet, p. 338 telescope, p. 342 space probe, p. 342 -Glossary at www.macmillanmh.com The Sun, Earth, and the Moon are part of a larger system called a solar system (SOH•luhr SIS•tuhm). A solar system is made up of a star and the objects that move around it. Earth is one of eight planets (PLAN•its) that move around the Sun in our solar system. A planet is a large body of rock or gas with a nearly round shape that revolves around a star. Some planets in our solar system are smaller than Earth. Some are larger. Many have one or more moons. All rotate. All revolve in a nearly circular orbit. It takes Earth about 365 days to complete one orbit. It takes Mercury only 88 Earth days to travel its orbit. Neptune takes 165 Earth years. The farther away a planet is from the Sun, the longer it takes to complete one orbit. Reading Skill Classify Technology Explore Planet Earth with the Secret Agents. Our Solar System Venus Sun Mercury Mars Earth 338 EXPLAIN Scientists have found over 100 planets that revolve around other stars. You can sometimes see Mercury, Venus, Mars, Jupiter, or Saturn in the night sky. These planets look like stars from Earth. However, like the Moon, planets do not make their own light. Planets appear to shine because sunlight reflects, or bounces, off them. Although these planets are larger than the Moon, they look tiny. The Moon seems large because it is close to Earth. The planets are farther away, so they look much smaller than the Moon. Sizing Up Planets Measure Work with a partner. Hold a marble about 30 centimeters away from you. Measure Have a partner hold a tennis ball about 5 meters away from you. Observe Which object seems larger? Why? Which object really is larger? Infer How can larger planets look smaller to us than smaller planets? Quick Check Classify Name an object in our solar system that is not a planet. Critical Thinking How would the Sun look from Mercury? Read a Diagram Where is Earth in our solar system? Clue: Diagrams can show the positions of things. Watch the planets at www.macmillanmh.com Jupiter Neptune Uranus Saturn 339 EXPLAIN What are the inner and outer planets? The four planets closest to the Sun are Mercury, Venus, Earth, and Mars. They are called the inner planets. The inner planets are among the smallest planets in our solar system. They are solid and made up of rocky material. They are warmer than the other planets because they are closer to the Sun. Inner Planets Mercury is the planet closest to the Sun. It is rocky and full of craters. Outer Planets Saturn is known for its beautiful rings made up of bits of ice and rock that revolve around the planet. Jupiter is the largest planet. It now has two red spots. The larger spot, shown here, is known as the Great Red Spot. 340 EXPLAIN The surface of Venus is covered with thick clouds that trap heat. This makes it the hottest planet. The planets farthest from the Sun are Jupiter, Saturn, Uranus, and Neptune. These are the outer planets. They are called “gas giants,” since they are largely made up of gases. They may have solid cores, but scientists do not know yet. Quick Check Classify Is Saturn an inner planet or an outer planet? Critical Thinking If Mercury is closer to the Sun than Venus, why is Venus hotter than Mercury? Earth is the only planet known to produce oxygen and to have liquid water and living things. Mars, the Red Planet, has reddish-brown soil and polar ice caps that contain frozen water. Uranus is called the “sideways planet” because it rotates on its side. Neptune is more than 2 billion miles from Earth. It has a Great Dark Spot similar to Jupiter’s Great Red Spot. 341 EXPLAIN How can we view the planets? Are there other planets? What is Neptune like? We cannot use just our eyes to find out. Special tools are needed. A telescope (TEL•uh•skohp) is a tool used to make objects far away appear closer and larger. A telescope works by gathering light with mirrors and lenses (LENZ•uhz). A lens is a clear material that helps us see objects in more detail. Another tool used is a space probe. A space probe is a machine that leaves Earth and travels through space. Some space probes land on planets. Others take pictures as they fly by planets and other objects in space. In 2006 the space probe New Horizon was launched. It will travel far beyond Neptune to find out about other space objects. Telescopes help us see planets and other objects in space. Quick Check Classify What kind of tool is the New Horizon spacecraft? Critical Thinking How could you see the Moon’s craters better? 342 EXPLAIN In 2004, two space probes landed rovers on Mars. The rovers explored its surface and sent pictures back to Earth. Visual Summary Our solar system is made up of the Sun, the planets, and other objects that revolve around the Sun. Our solar system has four inner planets and four outer planets. Telescopes and space probes are used to observe the planets and other objects in space. Think, Talk, and Write Main Idea What makes up our solar system? Vocabulary What is a planet? Name five planets. Classify Is Venus a planet or a star? Explain your answer. Critical Thinking What is the same about all of the planets in our solar system? Make a Study Guide Test Prep Which tool would BEST show details of Saturn? A binoculars B a microscope C a hand lens D a telescope Make a Trifold Book. Use it to summarize what you learned about Earth’s solar system. Math Link Solve a Problem In 2006 Saturn had 28 times as many known moons as Mars. Mars had two moons. How many moons did Saturn have? Art Link Planet Picture Suppose you could visit another planet. If you could stand on its surface, what would you see? Draw or paint a picture. Write the name of the planet on your picture. -Review Summaries and quizzes online at www.macmillanmh.com 343 EVALUATE Inquiry Skill: Observe You know that Earth is only one of the planets in our solar system. How do scientists learn about other planets? How do they learn about other objects, such as comets, that orbit the Sun? They observe the Sun, planets, moons, and other objects in our solar system to learn more about them. Learn It When you observe, you use one or more of your senses to learn about an object or event. Remember, your senses are sight, hearing, smell, taste, and touch. Scientists often use tools, such as binoculars, microscopes, and telescopes, to make their observations. They use their observations to draw conclusions about objects and events. Be Careful. It can be dangerous to observe things by tasting. You should not taste things in school unless your teacher tells you it is safe. Try It You can observe things, too. Look at the detail of this comet. Observe its color and shape. Look for unique features that help you identify what it is. What detail helps you know this is a comet and not a planet? 344 EXTEND Comets are mostly ice mixed with bits of rock and dust. Apply It The photos below show details of planets and other objects in our solar system. Observe each photo carefully. Use your observations to identify what each object is. Which details helped you to identify the objects? 345 EXTEND Lesson 4 The Stars The Sun is a star that is close to Earth. Other stars are in the sky. Why can’t we see them during the day? 346 ENGAGE Why do we see stars at night? Materials Purpose Understand why we do not see stars in the daytime sky. white chalk or white crayon black paper white paper measuring tape Procedure Draw a 3 cm dot with white chalk or crayon on black paper. Draw a 3 cm dot with white chalk or crayon on white paper. Measure Have your partner hold both papers 2 m away from you. Observe Which dot is easier to see? Step Draw Conclusions Infer Why do you think one dot was easier to see than the other? Infer Suppose the dots on the papers were stars. Why do you think you see stars only at night? Explore More Step Experiment Design an experiment to show how we sometimes see the Moon during the day. 347 EXPLORE What are stars? Main Idea Stars differ in several ways. Different stars are seen during different seasons. Vocabulary constellation, p. 349 -Glossary at www.macmillanmh.com Reading Skill Summarize Stars are glowing balls of hot gases that give off light and heat. The Sun is the only star in our solar system. It is the closest star to Earth. There are more stars in the sky than anyone can easily count. Stars are always in the sky. We cannot see stars in daytime because the Sun’s light prevents us from seeing them. The Sun seems bigger and brighter than other stars because it is closer to Earth. The Sun is only a medium-size star, however. It is much smaller and younger than many other stars. Other stars seem tiny and faint because they are so far away. Size is only one way stars differ. Some stars are brighter than others. Some are hotter. Blue stars are hottest. Red stars are coolest. Sizing Up Stars medium star small star 348 EXPLAIN large star giant star Stars are classified by size, color, and brightness. Constellations Long ago, people gazed at the stars. They thought groups of stars formed pictures in the night sky. We can still see those star groups today. A constellation (kon•stuh•LAY•shuhn) is a group of stars that seem to form a picture. Quick Check Summarize What are some ways that stars differ? Make a Constellation Find out about a constellation. Use chalk to draw it on a piece of black paper. Use a pencil point to poke holes in the pattern. Be Careful. Observe Trade papers with a partner. In a darkened room, hold your partner’s paper out at arm’s length toward a lamp or flashlight. What does the star pattern look like? Critical Thinking How is the Sun different from all other stars? The Big Dipper is shown by the bright yellow lines. It is part of the constellation Ursa Major, or the Great Bear. Communicate Tell your partner the name of your constellation. The Big Dipper is not a constellation. 349 EXPLAIN Why do we see different stars during different seasons? Each season, you can see different stars. As Earth revolves around the Sun, the dark part of Earth faces different directions. This movement gives us a different view of the nighttime sky. Find the constellation Orion below. In winter you can see Orion in the night sky. In summer Earth has moved to the other side of the Sun. When you look at the night sky in summer, you are facing away from Orion. Orion is in the daytime sky and cannot be seen. Stars and Seasons spring winter summer Orion fall Read a Diagram Why can Orion only be seen in winter? Quick Check Summarize Why do we see different stars from season to season? Critical Thinking Why might Orion have looked like a hunter to people long ago? 350 EXPLAIN Clue: Compare the direction that the dark part of Earth is facing in each season. Visual Summary Stars differ by size, brightness, and color. Think, Talk, and Write Main Idea What are stars? Vocabulary What is a constellation? Summarize Why do stars much Constellations are groups of stars that seem to form pictures in the night sky. larger than the Sun look much smaller than the Sun from Earth? Different constellations are seen during different seasons. Critical Thinking Do you think that you can see all the stars there are? Explain your answer. Make a Study Guide Make a Trifold Book. Use it to summarize what you learned about stars. Test Prep How would you describe the Sun? A a small star B a medium star C a giant star D a blue star Writing Link Write a Report Long ago, people thought the constellation Cassiopeia looked like a queen. Research this constellation or another one. Then write about it. Music Link Sing a Star Song Learn the words to the song “Twinkle, Twinkle, Little Star.” Write a verse of your own about stars to go with the tune. Read or sing the new words to the class. -Review Summaries and quizzes online at www.macmillanmh.com 351 EVALUATE Meet Orsola De Marco Do you ever wonder about the stars? Orsola De Marco does. She is an astrophysicist at the American Museum of Natural History in New York. An astrophysicist is a scientist who studies stars. Orsola studies stars that are found together in pairs. As far as we know, our Sun is a star that stands alone. Most stars in the universe have a partner. They are called binary stars. 352 EXTEND Meet a Scientist These binary stars orbit each other at a very close distance. Scientists think that one star is being absorbed by the other. The butterfly-shaped “wings” are probably caused by gases from the surface of the central star. Summarize A good summary states the main idea gives the most important details is brief Of course, Orsola cannot go is told in your own words to the stars to learn about them. Instead, she travels to Arizona, Hawaii, and Chile to use large telescopes. She gazes billions of miles into space to get a good look at binary stars. She watches how the stars affect each other. When a star gets old it becomes larger. If there is another star nearby, it might get eaten up, or absorbed, by the old star. No one is sure what will happen after that. Orsola is working to find out. Write About It Summarize Read the article with a partner. List the most important information in a chart. Then use the chart to summarize the article. Remember to start with a main-idea sentence and to keep your summary brief. -Journal Write about it online at www.macmillanmh.com 353 EXTEND CHAPTER 8 Review Visual Summary Lesson 1 Earth rotates and revolves around the Sun. Earth’s movement causes day and night and the seasons. axis, p. 319 Lesson 2 The Moon’s shape and position in the sky seem to change. Lesson 3 Earth is one of eight planets that revolve around the Sun. Lesson 4 Stars differ in several ways. Different stars are seen during different seasons. rotates, p. 318 constellation, p. 349 solar system, p. 338 craters, p. 332 space probe, p. 342 orbit, p. 320 star, p. 322 phase, p. 328 telescope, p. 342 1. Earth revolves around the Sun in a regular path called an . 2. A line through the center of a spinning object is an . 3. A group of stars that seems to form a picture is called a . 4. Faraway objects look closer when seen through a . 5. A star and the objects that orbit it make up a . 6. Every 24 hours Earth . 7. A machine that travels through space from Earth is a . Make a Study Guide Glue your lesson study guides to a piece of paper as shown. Use your study guide to review what you have learned in this chapter. 354 Fill each blank with the best term from the list. 8. Each shape of the Moon seen from Earth is known as a . 9. The Sun is a _____. 10. The hollow areas and pits on the Moon’s surface are _____. -Review Summaries and quizzes online at www.macmillanmh.com Answer each of the following in complete sentences. 11. Summarize What do the planets in our solar system have in common? How do they differ? Write several sentences to summarize this information. Space Exploration This photo shows a major event in space exploration. Make a time line of what you think were important events in space exploration. 12. Personal Narrative Look at the night sky. Write a journal entry about what you observe in the night sky. How does what you observe make you feel? 13. Observe Long ago, we could only rely on our eyes to learn about the Moon. What can you observe about the Moon by just looking at it? What other details might you be able to observe using a telescope? 14. Critical Thinking How might life on Earth change if Earth were farther away from the Sun? What if Earth were much closer? 15. Observe the Moon’s shape below. How much time must pass before the New Moon phase occurs? 16. What objects move through space, and how do they move? Draw a line that is 12 inches long. Mark off each inch to represent five years. Label each mark with the year. Mark the very beginning of your time line with the year 1950. End with the year 2010. Research some important events in space exploration. Mark on your time line each event and the year that it occurred. Which event on your time line do you think was most important? Why? Write about it. 1. Why is it warmer in summer than in winter? A There is more cloud cover in winter to block the Sun’s rays. B The Sun’s rays strike Earth’s surface more directly in summer. C The Sun’s rays strike Earth’s surface more directly in winter. D Earth is much closer to the Sun in summer than in winter. 355 Meteorologist Not all meteorologists work on TV. Some work as aviation meteorologists. They predict weather for airlines. Airline pilots need to know what weather will be like so people can travel safely. Other meteorologists gather data at weather stations in rain forests or at the North Pole and South Pole. The information they gather helps other scientists learn more about Earth’s climate. Meteorologists use technology to collect data about weather. To be a meteorologist, you need to study weather in college. You need good computer skills. You will also need to learn to use special weather tools and how to read radar scans and satellite photos. Here are some other Earth Science careers: • weather observer • climatologist • astronaut • astronomer 356 This meteorologist checks rainfall in the Amazon rain forest of Brazil. -Careers at www.macmillanmh.com