1. Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 1 Section 2 Telescopes Compare refracting telescopes with reflecting telescopes. Explain how the atmosphere limits astronomical observations, and explain how astronomers overcome these limitations. List the types of electromagnetic radiation that astronomers use to study objects in space. Objectives Chapter 1

2. Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 1 Section 2 Telescopes Telescopes A Telescope is an instrument that gathers electromagnetic radiation from objects in space and concentrates it for better observation. There are many different types of telescopes. Chapter 1

3. Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 1 Section 2 Telescopes Optical Telescopes Refracting Telescopes Telescopes that use lenses to gather and focus light are called refracting telescopes. A refracting telescope is shown on the next slide. Reflecting Telescope A telescope that uses a curved mirror to gather and focus light is called a reflecting telescope. A reflecting telescope is shown on the next slide. Chapter 1

4. Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 1 Section 2 Telescopes Optical Telescopes Refracting Telescopes Telescopes that use lenses to gather and focus light are called refracting telescopes. A refracting telescope is shown on the next slide. Reflecting Telescope A telescope that uses a curved mirror to gather and focus light is called a reflecting telescope. A reflecting telescope is shown on the next slide. Chapter 1

5. Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 1 Section 2 Telescopes Refracting and Reflecting Telescopes Chapter 1

6. Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 1 Section 2 Telescopes Optical Telescopes, continued Very Large Reflecting Telescopes In some very large reflecting telescopes, several mirrors work together to collect light and focus it in the same area. Chapter 1

7. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Most optical telescopes used by professional astronomers are housed in buildings called observatories. Using Optical Telescopes Observatories often have dome-shaped roofs that can be opened up for viewing.

8. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu The twin Keck reflecting telescopes have segmented mirrors 10 m wide. Large Reflecting Telescopes Until 2000, these mirrors were the largest reflectors ever used.

9. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Large Reflecting Telescopes In 2000, the European Southern Observatory’s telescope, in Chile, consisted of four 8.2-m reflectors, making it the largest optical telescope in use.

10. Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 1 Section 2 Telescopes Optical Telescopes, continued Optical Telescopes and the Atmosphere The light gathered by telescopes on the Earth is affected by the atmosphere. Optical Telescopes in Space To avoid interference by the atmosphere, scientists have put telescopes in space

11. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu The Hubble Space Telescope was launched in 1990 by the space shuttle Discovery. Hubble Space Telescope In December 1993, a team of astronauts repaired the Hubble Space Telescope by installing a set of small mirrors designed to correct images obtained by the faulty mirror.

12. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Two more missions to service Hubble were carried out in 1997 and 1999. Hubble Space Telescope Among the objects viewed by Hubble after it was repaired in 1999 was a large cluster of galaxies known as Abell 2218.

13. Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 1 Section 2 Telescopes Nonoptical Telescopes Radio Telescopes Radio telescopes detect radio waves. Because radio wavelengths are much larger than optical wavelengths, radio telescopes much be very large. Linking Radio Telescopes Astronomers can get more detailed images of the universe by linking radio telescopes together. Working together, the telescopes function as a single giant telescope.

14. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Radio Telescopes Unlike visible light, radio waves pass freely through Earth’s atmosphere. Because of this, radio telescopes are useful 24 hours per day under most weather conditions. Radio waves reaching Earth’s surface strike the large, concave dish of a radio telescope. This dish reflects the waves to a focal point where a receiver is located.

15. Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 1 Section 2 Telescopes Nonoptical Telescopes, continued Nonoptical Telescopes in Space Because most electromagnetic waves are blocked by the Earth’s atmosphere, scientists have placed ultraviolet telescopes, infrared telescopes, gamma-ray telescopes, and X-ray telescopes in space.

16. Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 1 Electromagnetic Radiation The electromagnetic spectrum includes the entire range of radio waves, infrared radiation, visible light, ultraviolet radiation, X-rays, and gamma rays.

17. Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 1 Four Views of the Crab Nebula Different type of telescopes collect electromagnetic radiation at different wavelengths. Astronomers are able to learn a great deal about the Crab Nebula by examining these different images. The images are shown at different scales.

18. Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 1 Section 2 Telescopes The Electromagnetic Spectrum What Is the Electromagnetic Spectrum? The electromagnetic spectrum is made up of all of the wavelengths of electromagnetic radiation. Detecting Electromagnetic Radiation Visible light is only a small band of the electromagnetic spectrum. Radio waves, microwaves, infrared light, ultraviolet light, X rays, and gamma rays— are invisible to the human eye.

19. Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 1 Section 2 Telescopes The Electromagnetic Spectrum

20. Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 1 “Gamma Rays” 1x10 -12 m

21. Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 1 Individual Atoms! (Xe on Ni) 5x10 -11 m

22. Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 1 “X-Rays” 1x10 -10 m

23. Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 1 Width of DNA Helix 2x10 -9 m

24. Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 1 “Average Virus” 7.5x10 -8 m

25. Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 1 “Ultraviolet” 5x10 -8 m

26. Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 1 “Average Bacterium” 0.2 – 2.0x10 -6 m Staphylococcus Credit: E. Coli; Rocky Mountain Laboratories, NIAID, NIH

27. Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 1 “Visible” light 5x10 -7 m

28. Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 1 “Infared” 1x10 -5 m

29. Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 1 “High Microwave” 1x10 -2 m

30. Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 1 Height of “Average” Human 1.7x10 0 m

31. Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 1 “Radio/Low Microwave” 1x10 -2 – 1x10 3 m