Telescopes: Types, Limitations, and Observations

1. Chapter 1 Section 2Telescopes Objectives • Compare refracting telescopes with reflecting telescopes. • Explain how the atmosphere limits astronomical observations, and explain how astronomers overcome these limitations. • Listthe types of electromagnetic radiation that astronomers use to study objects in space.

2. Chapter 1 Section 2Telescopes 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.

3. Chapter 1 Section 2Telescopes 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 TelescopeA 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.

4. Chapter 1 Section 2Telescopes 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 TelescopeA 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.

5. Chapter 1 Section 2Telescopes Refracting and Reflecting Telescopes

6. Chapter 1 Section 2Telescopes Optical Telescopes, continued • Very Large Reflecting TelescopesIn some very large reflecting telescopes, several mirrors work together to collect light and focus it in the same area.

7. Using Optical Telescopes • Most optical telescopes used by professional astronomers are housed in buildings called observatories. • Observatories often have dome-shaped roofs that can be opened up for viewing.

8. Large Reflecting Telescopes • The twin Keck reflecting telescopes have segmented mirrors 10 m wide. • Until 2000, these mirrors were the largest reflectors ever used.

9. 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. Large Reflecting Telescopes

10. Section 2Telescopes Optical Telescopes, continued • Optical Telescopes and the Atmosphere The light gathered by telescopes on the Earth is affected by the atmosphere. • Optical Telescopes in SpaceTo avoid interference by the atmosphere, scientists have put telescopes in space

11. Hubble Space Telescope • The Hubble Space Telescope was launched in 1990 by the space shuttle Discovery. • 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. Hubble Space Telescope • Two more missions to service Hubble were carried out in 1997 and 1999. • Among the objects viewed by Hubble after it was repaired in 1999 was a large cluster of galaxies known as Abell 2218.

13. Section 2Telescopes 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 TelescopesAstronomers can get more detailed images of the universe by linking radio telescopes together. Working together, the telescopes function as a single giant telescope.

14. RadioTelescopes • 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. Section 2Telescopes Nonoptical Telescopes, continued • Nonoptical Telescopes in SpaceBecause 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. The electromagnetic spectrum includes the entire range of radio waves, infrared radiation, visible light, ultraviolet radiation, X-rays, and gamma rays. Electromagnetic Radiation

17. 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. Four Views of the Crab Nebula

18. Section 2Telescopes The Electromagnetic Spectrum • What Is the Electromagnetic Spectrum? The electromagnetic spectrum is made up of all of the wavelengths of electromagnetic radiation. • Detecting Electromagnetic RadiationVisible 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. Section 2Telescopes The Electromagnetic Spectrum

20. “Gamma Rays” 1x10-12 m

21. Individual Atoms! (Xe on Ni) 5x10-11 m

22. “X-Rays” 1x10-10 m

23. Width of DNA Helix 2x10-9 m

24. “Average Virus” 7.5x10-8 m

25. “Ultraviolet” 5x10-8 m

26. “Average Bacterium” 0.2 – 2.0x10-6 m Staphylococcus Credit: E. Coli; Rocky Mountain Laboratories, NIAID, NIH

27. “Visible” light 5x10-7 m

28. “Infared” 1x10-5 m

29. “High Microwave” 1x10-2 m

30. Height of “Average” Human 1.7x100 m

31. “Radio/Low Microwave” 1x10-2 – 1x103 m