1. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 3 Mapping the Stars Explain how constellations are used to organize the night sky. Describe how the altitude of a star is measured. Explain how the celestial sphere is used to describe the location of objects in the sky. Compare size and scale in the universe, and explain how red shift indicates that the universe is expanding. Objectives Chapter J1

2. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 3 Mapping the Stars Patterns in the Sky Constellations Help Organize the Sky A constellation is a region of the sky. Each constellation shares a border with neighboring constellations. Seasonal Changes As Earth revolves around the sun, the apparent locations of the constellations change from season to season. Chapter J1

3. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Spring Constellations in the Northern Hemisphere Section 3 Mapping the Stars Chapter J1

4. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 3 Mapping the Stars Finding Stars in the Night Sky You can describe the location of a star or planet by using an instrument called an astrolabe and the following points of reference: The zenith is the point in the sky directly above on observer on Earth. The altitude is the angle between an object in the sky and the horizon. The horizon is the line where the sky and the Earth appear to meet. Chapter J1

5. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Zenith, Altitude, and Horizon Section 3 Mapping the Stars Chapter J1

6. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 3 Mapping the Stars Finding Stars in the Night Sky, continued Using an astrolabe allows you to describe where a star or planet is relative to you. Scientists need a different method that describes location independently of the observer’s location. Astronomers describe the location of a star or planet in terms of the celestial sphere. Chapter J1

7. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu The Celestial Sphere Section 3 Mapping the Stars Chapter J1

8. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 3 Mapping the Stars Describing a Star’s Position Click below to watch the Visual Concept. You may stop the video at any time by pressing the Esc key. Visual Concept Chapter J1

9. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 3 Mapping the Stars The Size and Scale of the Universe In the 1600s, Nicolaus Copernicus noticed that the planets appeared to move relative to each other but that the stars did not. Thus, he thought that the stars must be much farther away than the planets. Measuring Distance in Space A light-year is a unit of length equal to the distance that light travels in 1 year. Chapter J1

10. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 3 Mapping the Stars The Size and Scale of the Universe, continued It is important to consider scale when thinking about the universe. Although stars looks tiny in the night sky, remember that they are actually a lot larger than Earth. Chapter J1

11. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 3 Mapping the Stars The Doppler Effect What Is the Doppler Effect? Have you ever noticed that when a driver in an approaching car blows the horn, the horn sounds higher pitched as the car approaches and lower pitched after the car passes? This effect is called the Doppler effect. An Expanding Universe The Doppler effect has been used to discover that galaxies are rapidly moving apart from each other. Chapter J1

12. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 3 Mapping the Stars Red Shift Click below to watch the Visual Concept. You may stop the video at any time by pressing the Esc key. Visual Concept Chapter J1

13. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Reading Read each of the passages. Then, answer the questions that follow each passage. Standardized Test Preparation Chapter J1

14. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Standardized Test Preparation 2. Why don’t upright objects cast a shadow when the sun is at its zenith? F because the sun is directly overhead G because the summer solstice is occurring H because the sun is below the horizon I because the sun is at its zenith on the longest day of the year Chapter J1

15. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Standardized Test Preparation INTERPRETING GRAPHICS The diagram on the following slide shows a galaxy moving in relation to four observers. The concentric circles illustrate the Doppler effect at each location. Use the diagram to answer the questions that follow. Chapter J1

16. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Standardized Test Preparation Chapter J1

17. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Standardized Test Preparation 1. Which of the following observers would see the light from the galaxy affected by redshift? A observers 1 and 2 B observer 3 C observers 3 and 4 D observers 1 and 4 Chapter J1

18. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Standardized Test Preparation 1. Which of the following observers would see the light from the galaxy affected by redshift? A observers 1 and 2 B observer 3 C observers 3 and 4 D observers 1 and 4 Chapter J1

19. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Standardized Test Preparation 2. Which of the following observers would see the light from the galaxy affected by blueshift? F observer 1 G observers 2 and 4 H observers 3 and 4 I observer 2 Chapter J1

20. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Standardized Test Preparation 2. Which of the following observers would see the light from the galaxy affected by blueshift? F observer 1 G observers 2 and 4 H observers 3 and 4 I observer 2 Chapter J1

21. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Standardized Test Preparation 3. How would the wavelengths of light detected by observer 4 appear? A The wavelengths would appear shorter than they really are. B The wavelengths would appear longer than they really are. C The wavelengths would appear unchanged. D The wavelengths would alternate between blue and red. Chapter J1

22. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Standardized Test Preparation 3. How would the wavelengths of light detected by observer 4 appear? A The wavelengths would appear shorter than they really are. B The wavelengths would appear longer than they really are. C The wavelengths would appear unchanged. D The wavelengths would alternate between blue and red. Chapter J1

23. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Standardized Test Preparation MATH Read each of the following questions, and choose the best answer. Chapter J1

24. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Standardized Test Preparation 1. If light travels 300,000 km/s, how long does light reflected from Mars take to reach Earth when Mars is 65,000,000 km away? A 22 s B 217 s C 2,170 s D 2,200 s Chapter J1

25. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Standardized Test Preparation 1. If light travels 300,000 km/s, how long does light reflected from Mars take to reach Earth when Mars is 65,000,000 km away? A 22 s B 217 s C 2,170 s D 2,200 s Chapter J1

26. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Standardized Test Preparation 4. If the altitude of a star is 37°, what is the angle between the star and the zenith? F 143° G 90° H 53° I 37° Chapter J1

27. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Standardized Test Preparation 4. If the altitude of a star is 37°, what is the angle between the star and the zenith? F 143° G 90° H 53° I 37° Chapter J1

28. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Standardized Test Preparation 5. You are studying an image made by the Hubble Space Telescope. If you observe 90 stars in an area that is 1 cm 2, which of the following estimates is the best estimate for the number of stars in 15 cm 2 ? A 700 B 900 C 1,200 D 1,350 Chapter J1

29. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Standardized Test Preparation 5. You are studying an image made by the Hubble Space Telescope. If you observe 90 stars in an area that is 1 cm 2, which of the following estimates is the best estimate for the number of stars in 15 cm 2 ? A 700 B 900 C 1,200 D 1,350 Chapter J1