1. Telescopes

2. Telescope An instrument that collects electromagnetic radiation from objects in space Concentrates the electromagnetic radiation for better observation

3. Optical Telescopes  Most common type of telescope  Used to study visible light from objects in universe  Enables you to see millions of stars

4. Refracting Telescopes  Use lenses to gather and focus light

5. Two Disadvantages of Refracting Telescopes 1. Images cannot be perfectly focused 2. Size of objective lens limits the size of the telescope

6. Reflecting Telescopes  Use a curved mirror & a flat mirror to gather & focus light

7. Three Advantages of Reflecting Telescopes 1. Large mirrors can gather more light. 2. Flaws in the mirror’s glass do not affect the light. 3. Mirrors can focus all colors of light at the same time.

8. Optical Telescopes & Atmosphere  Air above telescope makes starlight shimmer & blur.  Light pollution affects ability to see dim objects.

9. Placement of Telescopes  Dry environments  Mountaintops  Less light pollution  Less air pollution  Air is thinner  Space

10. Electromagnetic Spectrum

11. Detecting Electromagnetic Radiation  EM spectrum = all of the wavelengths of electromagnetic radiation  Each color of light is a different wave- length.  Humans can see radiation from red light (long wave) to blue light (shorter wave).

12. Nonoptical Telescopes  Used to study invisible radiation  Each type of EM radiation gives different clues about objects

13. Detecting Electromagnetic Radiation  Visible light is small part of EM spectrum.  Most of EM spectrum is invisible  Radio waves (longest waves)  Microwaves  Infrared waves  Ultraviolet wav es  X-rays  Gamma waves (shortest waves)

14. Radio Telescopes  Detect radio waves  Can be linked with other radio telescopes  Surface does not have to be solid  Must be much larger than optical telescopes  Radio waves can be as large as a building

15. Radio Telescope & VLA

16. Nonoptical Telescopes in Space  Placed in space because most EM radiation is blocked by Earth’s atmosphere