Lesson 4 Galaxies and the Universe

Transcription

1 Lesson 4 Galaxies and the Universe Student Labs and Activities Page Launch Lab 66 Content Vocabulary 67 Lesson Outline 68 MiniLab 70 Content Practice A 71 Content Practice B 72 School to Home 73 Key Concept Builders 74 Enrichment 78 Challenge 79 Lab A 82 Lab B 85 Lab C 88 Chapter Key Concepts Builder 89 Stars and Galaxies 65

2 Launch Lab LESSON 4: 20 minutes Does the universe move? Scientists think the universe is expanding. What does that mean? Are stars and galaxies moving away from each other? Is the universe moving? Procedure 1. Read and complete a lab safety form. 2. Use a marker to make three dots 5 7 cm apart on one side of a large round balloon. Label the dots A, B, and C. The dots represent galaxies. 3. Blow up the balloon to a diameter of about 8 cm. Hold the balloon closed as your partner uses a measuring tape to measure the distance between each galaxy on the balloon s surface. Record the distances on the table in the Data and Observations section below. 4. Repeat step 3 two more times, blowing up the balloon a little more each time. Data and Observations Balloon Size A B (cm) B C (cm) A C (cm) Small Medium Large Think About This 1. What happened to the distances between galaxies as the balloon expanded? 2. If you were standing in one of the galaxies, what would you observe about the other galaxies? 3. Key Concept If the balloon were a model of the universe, what do you think might have caused galaxies to move in this way? 66 Stars and Galaxies

3 Content Vocabulary LESSON 4 Galaxies and the Universe Directions: Answer each question or respond to each statement on the lines provided. You must include the terms below in your answer or response. Big Bang theory dark matter Doppler shift galaxy 1. What do scientists know about dark matter? 2. According to the Big Bang theory, how old is the universe? Explain. 3. What are three types of galaxies? 4. According to the Big Bang theory, how has the universe changed since its beginning? 5. Explain how the Doppler shift occurs as an emergency vehicle passes with its sirens blaring. 6. In which galaxy do you live? Explain. Stars and Galaxies 67

4 Lesson Outline LESSON 4 Galaxies and the Universe A. Galaxies 1. Huge collections of stars are called, each of which can contain hundreds of billions of. 2. The force that holds stars and galaxies together is. a. Most matter in galaxies is matter, which emits no light at any wavelength. b. More than 90 percent of the universe s mass is thought to be matter, but scientists do not know what type of material it contains. 3. The three main kinds of galaxies are,, and galaxies. a. A(n) galaxy has a bulging central disk of stars with arms that radiate from the central disk. b. A(n) galaxy can have the shape of a basketball or a football but lack internal. c. A(n) galaxy does not have a clear shape or structure. 4. pulls galaxies together in groups called. a. Clusters clump into larger groups called. b. Regions of between the superclusters cause the to have a structure like a sponge. B. The Milky Way 1. Our planet, Earth, is part of a(n) system that is in the galaxy. 2. The Milky Way is a(n) galaxy that contains gas,, and almost 200 billion. 3. The Milky Way is part of a(n) of about 30 galaxies called the. 68 Stars and Galaxies

5 Lesson Outline continued 4. and the other planets of our solar system are located in a spiral arm of the Milky Way. C. The Big Bang Theory 1. By looking into, astronomers can look back in. 2. Based on the theory, the began from one point billions of years ago, and it has been since then. 3. Scientists think that the began 13 to 14 billion years ago as a dense, hot form that was too hot even for a. When the universe cooled, began to form and pulled the stars into galaxies. to exist. b. The universe is, and are moving away from one another. c. Scientists can measure the at which galaxies move away from of. by observing wavelengths 4. Sound waves and light waves when the source emitting those waves moves toward you. In contrast, sound waves and light waves from you. when the source emitting those waves moves away a. When a wavelength shifts to a different wavelength, the shift is called the. b. In our expanding universe, galaxies are moving away from us, and the coming from those galaxies is red-shifted. c. The farther a galaxy is from us, the the galaxy is moving away from us and the greater the shift is toward the end of the spectrum. 5. Scientists have observed that, over time, are moving away from at an increasingly faster pace. 6. Scientists are researching a force called that could be pushing galaxies apart. Stars and Galaxies 69

6 MiniLab LESSON 4: 20 minutes Can you identify a galaxy? The Hubble Space Telescope, shown in your textbook, is an orbiting telescope that gives astronomers clear pictures of the night sky. What kinds of galaxies can you see in pictures taken by the Hubble Telescope? Procedure 1. Study each image on the Hubble Space Telescope image sheet. For each image, identify at least two galaxies. Are they spiral, elliptical, or irregular? Write your observations in the Data and Observations section below, labeled with the letter of the image. Data and Observations Analyze and Conclude 1. Draw Conclusions Why are some galaxies easier to identify than others? 2. Infer What interactions do you see among some of the galaxies? 3. Key Concept Do you think the shapes of galaxies can change over time? Why or why not? 70 Stars and Galaxies

7 Content Practice A LESSON 4 Galaxies and the Universe Directions: On the line before each definition, write the letter of the term that matches it correctly. Each term is used only once. 1. includes a region called the central bulge 2. wavelength of light or sound depends on the position of the observer 3. can form from the gravitational pull of neighboring galaxies 4. spiral galaxy that contains our solar system 5. the light emitted from galaxies as the universe expands 6. cluster of galaxies that contains the Milky Way A. galaxy B. gravity C. dark matter D. spiral galaxy E. elliptical galaxy F. irregular galaxy G. cluster H. Milky Way I. Big Bang theory J. Doppler shift K. red-shifted L. dark energy M. Local Group 7. force that might explain the accelerating expansion of the universe percent of the universe s mass 9. explains the origin of the universe 10. huge collection of stars; the Milky Way, for example 11. shaped like a sphere or a football 12. group of galaxies 13. the force that holds galaxies together Stars and Galaxies 71

8 Content Practice B LESSON 4 Galaxies and the Universe Directions: Circle the term in parentheses that correctly completes each sentence. 1. A galaxy can contain hundreds of billions of (stars, universes). 2. Galaxies are held together by the force of (dark energy, gravity). 3. The three main types of galaxies are spiral, elliptical, and (irregular, clustered). 4. A spiral (solar system, galaxy) has a central bulge and two or more curved arms. 5. An elliptical galaxy is shaped like a (sphere, cube). 6. Irregular galaxies can form from the gravitational pull of nearby (black holes, galaxies). 7. (Gravity, Radiation) holds galaxies together in groups, clusters, or superclusters. 8. The Milky Way is (a spiral, an elliptical) galaxy that contains our solar system. 9. Two galaxies in the Local Group are the Milky Way and (Virgo, Andromeda). 10. The Big Bang theory is an explanation of the (origin, contraction) of the universe. 11. The Big Bang theory states that the universe started from one point and has been (rotating, expanding) ever since. 12. The Doppler shift is evidence that galaxies are getting (farther apart, closer together) and that the universe is expanding. 13. As galaxies travel outward from Earth, the (noise, light) they emit shifts toward the red end of the electromagnetic spectrum. 14. The more distant a galaxy is, the faster it is moving (away from, toward) Earth. 72 Stars and Galaxies

9 School to Home LESSON 4 Galaxies and the Universe Did you know? Astronomers estimate that there are about stars in the universe. When it is written, this number is 1,000,000,000,000,000,000,000! Yet, most of the matter in the universe is dark matter matter that can t be seen. To get a sense of the universe, you will make a simple model. For this activity, you will need a large, empty area on the floor, a black cloth or black construction paper to cover the area, and a teaspoon of salt. 1. Your model universe should be at least 3 m 3 m in size. Cover the area with the black cloth or construction paper. 2. Stand at one end of your universe with the spoonful of salt in your hand. Quickly flick your wrist so the salt scatters over the entire area. 3. Observe your model. 4. What does the black area of your model represent? 5. What do the grains of salt represent? 6. Use your model to describe a universe. Stars and Galaxies 73

10 Key Concept Builder LESSON 4 Galaxies and the Universe Key Concept What are the major types of galaxies? Directions: On the line before each statement, write SP if the statement describes spiral galaxies, EL if the statement describes elliptical galaxies, or IR if the statement describes irregular galaxies. 1. contain spiral arms that begin at a central disk 2. A spherical halo surrounds the disk. 3. might have formed by the gravitational merging of two or more spiral galaxies 4. The Milky Way is an example. 5. have a higher percentage of old, red stars than spiral galaxies have 6. contain little or no gas or dust 7. The halo consists of globular clusters and older, redder stars. 8. contain many young stars 9. form from the gravitational pull of neighboring galaxies 10. have areas of intense star formation 74 Stars and Galaxies

11 Key Concept Builder LESSON 4 Galaxies and the Universe Key Concept What are the major types of galaxies? Directions: On the line before each statement, write T if the statement is true or F if the statement is false. If the statement is false, change the underlined word(s) to make it true. Write your changes on the lines provided. 1. A huge collection of stars is called a supernova. 2. A galaxy contains stars, stellar remnants, gas, dust, and black holes. 3. Galaxies can change over time. They rotate, gravitationally interact, and can merge. 4. The universe contains hundreds of billions of galaxies, and each galaxy can contain hundreds of billions of stars. 5. Most of the matter in galaxies is elliptical and emits no light at any wavelength. 6. Galaxies are described by their apparent mass spiral, elliptical, and irregular. 7. Spiral galaxies are thicker near the center. This region is called the central bulge. 8. Elliptical galaxies may have been formed by the merging of two or more spiral galaxies. 9. Galaxies shaped like a sphere, or a football, are classified as spiral. 10. Irregular galaxies contain many young stars and have areas of intense star formation. 11. Irregular galaxies can result from the nuclear pull of neighboring galaxies. 12. Galaxies are held together by gravity in groups called spirals. Stars and Galaxies 75

12 Key Concept Builder LESSON 4 Galaxies and the Universe Key Concept What is the Milky Way, and how is it related to the solar system? Directions: Complete this concept map by writing the correct terms from the word bank in the spaces provided. Each term is used only once. Andromeda clusters Local Group Milky Way the Moon solar system the Sun superclusters Virgo Universe Earth 76 Stars and Galaxies

13 Key Concept Builder LESSON 4 Galaxies and the Universe Key Concept What is the Big Bang theory? Directions: On each line, write the term from the word bank that correctly completes each sentence. Some terms may be used more than once or not at all. atoms Big Bang theory closer together dark energy Doppler shift farther apart galaxy gravity shift universe 1. The Big Bang theory is an explanation of what has happened since the beginning of the. 2. As the expands, space stretches and galaxies move away from each other. 3. If the distance between galaxies is increasing, then everything must have been in the past. 4. At the beginning, the universe was so hot and dense that did not yet exist. 5. The universe cooled, atoms formed, and pulled the atoms into galaxies. 6. The fact that distant galaxies and clusters are moving away from Earth is one piece of evidence that supports the. 7. As stars move away from Earth, the electromagnetic radiation they emit appears to toward the red end of the spectrum. 8. A distance to a faraway is proportional to its red-shift. 9. The is the change in frequency of a wave for an observer moving toward or away from the wave source. 10. The expansion of the universe has been accelerating, which suggests that a force called might be involved in pushing galaxies apart. Stars and Galaxies 77

14 Enrichment LESSON 4 Hubble, Galaxies, and Expansion Edwin Hubble, who lived from 1889 to 1953, has been called the greatest astronomer since the times of Galileo, Kepler, and Newton. His name is attached to many things of everyday astronomical life. Among them are Hubble s Law, the Hubble Galaxy classification, the Hubble Sequence, the Hubble Constant, the Hubble Redshift Distance relation, and the Hubble Space Telescope. Edwin Hubble was born in a small town in Missouri and attended the University of Chicago. He received an undergraduate degree in astronomy and math, a graduate degree in law, and a doctorate in astronomy. After working as an attorney in Kentucky and serving in WWI, he decided that he was bored with law and went back to his studies in astronomy. Theory of Relativity In 1919, when Hubble began work at the Mount Wilson Observatory in California, he was researching nebulae, which are fuzzy patches of light in the sky. At this time many astronomers still thought that the Milky Way galaxy was the entire universe, and that it was static and unchanging. Albert Einstein had already introduced his general theory of relativity Applying Critical-Thinking Skills Directions: Respond to each statement. and produced a model of space based on that theory, claiming that space was curved by gravity, and therefore it must be able to expand or contract. He found this assumption so far fetched, however, that he revised his theory, stating that the universe was static and immobile. Hubble s Work By the 1920s, Hubble had developed a galaxy classification system and established that there were other galaxies beyond the Milky Way. In the 1930s, by observing redshifts in the light wavelengths emitted by the galaxies, he saw that galaxies were moving away from each other at a rate constant to the distance between them (Hubble s Law). The farther away they were, the faster they receded. This information led to the calculation of the point where the expansion began and provided the first evidence for the Big Bang theory, which describes the birth and evolution of the universe. Following these discoveries by Hubble, Einstein was quoted as having said that second-guessing his original findings about the nature of the universe was the biggest blunder of his life. 1. Explain why the discovery that the universe is expanding can be used as evidence that the Big Bang occurred, even though no one saw it. 2. Hypothesize why Einstein considered his revision of his theory about the nature of the universe to be the biggest blunder of his life. 78 Stars and Galaxies

15 Challenge LESSON 4 Be a Citizen-Scientist! You can be a citizen-astronomer by participating in Galaxy Zoo, which is a project of the Sloan Digital Sky Survey. Volunteer members of the project help classify galaxies in an online image bank, which contains a data set of a million galaxies. In part 1 of the project, users split images of galaxies into ellipticals or spirals and recorded the direction of the arms. Project directors found that the classifications from Galaxy Zoo members were as good as those completed by professional astronomers, and parents found that their children were better at it than they were. The project is continuing with classifications of galaxy shapes. Participate in and Research the Galaxy Zoo Project 1. Search the Sloan Digital Sky Survey for Galaxy Zoo. Then read How to Take Part, register, and complete the tutorial. 2. Participate in three classification sessions, and keep a journal of your activity and reactions. 3. Research and describe three discoveries that Galaxy Zoo members have made that have provided astronomers with important information. Stars and Galaxies 79

16 Lab A 3 class periods Describe a Trip Through Space Imagine you could travel through space at speeds even faster than light. Based on what you have learned in this chapter, where would you choose to go? What would you like to see? What would it be like to move through the Milky Way and out into distant galaxies? Would you travel with anyone or meet any characters? Write a book describing your trip through space. Question Where will your trip take you, and how will you describe it? How can you write a fictional, but scientifically accurate, story about your trip? Will you make a picture book? If so, will you sketch your own pictures, use diagrams or photographs, or both? Will your book be mostly words, or will it be like a graphic novel? How can you draw your readers into the story? Materials paper colored pencils astronomy magazines string glue scissors Safety Procedure 1. Write ideas about where your trip will take you, how you will travel, what will happen along the way, and who or what you might meet. Lab Tips Think about your audience as you plan your book. Are you writing it for young children or for students your own age? What kinds of books do you and your friends enjoy reading? What metaphors or other kinds of figurative language can you add to your writing that will draw readers into your story? 82 Stars and Galaxies

17 Lab A continued 2. Complete the graphic organizer below. Use it to help you organize your ideas. My Trip Through Space method of travel 3. Write an outline of your story. Use it to guide you as you write the story. 4. List things you will need to research, pictures you will need to find or draw, and any other materials you will need. How will you bind your book? Will you make more than one copy? 5. Write your book. Add pictures or illustrations. Bind the pages together into book form. Stars and Galaxies 83

18 Lab A continued 6. Have a friend read your book and tell you if you succeeded in telling your story in an engaging way. What suggestions does your friend have for improvement? 7. Revise and improve the book based on your friend s suggestions. Analyze and Conclude 8. Research Information What new information did you learn as you did research for your book? 9. Calculate how many light-years you traveled from Earth. 10. Draw Conclusions How would your story be limited if you could only travel at the speed of light? 11. The Big Idea How does your story help people understand the size of the universe, what it contains, and how gravity affects it? Communicate Your Results You may wish to make a copy of your book and give it to the school library or add it to a library of books in your classroom. Remember to use scientific methods. Make Observations Ask a Question Form a Hypothesis Test your Hypothesis Analyze and Conclude Communicate Results 84 Stars and Galaxies

19 Lab B 3 class periods Describe a Trip Through Space Imagine you could travel through space at speeds even faster than light. Based on what you have learned in this chapter, where would you choose to go? What would you like to see? What would it be like to move through the Milky Way and out into distant galaxies? Would you travel with anyone or meet any characters? Write a book describing your trip through space. Question Where will your trip take you, and how will you describe it? How can you write a fictional, but scientifically accurate, story about your trip? Will you make a picture book? If so, will you sketch your own pictures, use diagrams or photographs, or both? Will your book be mostly words, or will it be like a graphic novel? How can you draw your readers into the story? Materials paper colored pencils astronomy magazines string glue scissors Safety Procedure 1. Write ideas about where your trip will take you, how you will travel, what will happen along the way, and who or what you might meet. Lab Tips Think about your audience as you plan your book. Are you writing it for young children or for students your own age? What kinds of books do you and your friends enjoy reading? What metaphors or other kinds of figurative language can you add to your writing that will draw readers into your story? Stars and Galaxies 85

20 Lab B continued 2. Draw a graphic organizer such as the one in your textbook. Use it to help you organize your ideas. 3. Write an outline of your story. Use it to guide you as you write the story. 4. List things you will need to research, pictures you will need to find or draw, and any other materials you will need. How will you bind your book? Will you make more than one copy? 5. Write your book. Add pictures or illustrations. Bind the pages together into book form. 6. Have a friend read your book and tell you if you succeeded in telling your story in an engaging way. What suggestions does your friend have for improvement? 7. Revise and improve the book based on your friend s suggestions. 86 Stars and Galaxies

21 Lab B continued Analyze and Conclude 8. Research Information What new information did you learn as you did research for your book? 9. Calculate how many light-years you traveled from Earth. 10. Draw Conclusions How would your story be limited if you could only travel at the speed of light? 11. The Big Idea How does your story help people understand the size of the universe, what it contains, and how gravity affects it? Communicate Your Results You may wish to make a copy of your book and give it to the school library or add it to a library of books in your classroom. Extension Remember to use scientific methods. Make Observations Ask a Question Form a Hypothesis Test your Hypothesis Analyze and Conclude Communicate Results Combine your book with books written by other students in your class to make an almanac of the universe. Add pages that give statistics and other interesting facts about the universe. Stars and Galaxies 87

22 Lab C A Space Science Book Fair Directions: Use the information and data from the Lab Describe a Trip Through Space to perform this lab. You have written a book that combines facts about the universe with an interesting story line. Reach a greater audience by summarizing your book in poster form for a book fair. For your poster, consider which images from your book or elsewhere would best communicate your story. Next, write a synopsis, or summary, of your story that would make people want to buy your book. Then, create a poster that you can present to your classmates or to younger classes. Remember to make your poster at a scale that can be seen by your entire audience. Please note that you must complete Lab B before beginning Lab C. Also, have your teacher approve your design and safety procedures before beginning your experiment. 88 Stars and Galaxies

23 Chapter Key Concepts Builder Stars and Galaxies End-of-Chapter Practice Directions: Work with a small group to create a model of some aspect of the universe. Brainstorm ideas with your group. To get started, make a list of questions about stars and galaxies. Your questions might already have answers (or at least theories), or they might be unanswered questions that scientists could investigate in the future. Questions with Answers or Theories: Questions Without Answers or Theories: With your group, choose a question from each list. Then decide how you would answer the question. My Answer: My Answer: Plan your model with your group. Model Design: Materials Needed: Responsibilities: Finally, create a model that will help answer your questions. Share your model with the class and explain how it answers your questions. Display Requirements: clear and detailed answers to questions organized plan imaginative model that supports answers 100 percent participation Stars and Galaxies 89