Chapter 21: Stars, Galaxies, Universe Section 1: telescopes

1. Chapter 21: Stars, Galaxies, UniverseSection 1: telescopes • Key concepts: What are the regions of the electromagnetic spectrum? What are telescopes and how do they work? Where are most large telescopes located? • Key terms: Telescope, electromagnetic radiation, visible light, wavelength, spectrum, optical telescope, refracting telescope, convex lens, reflecting telescope, radio telescope, observatory

2. Telescopes • A telescope is a device that makes distance objects appear closer. • Galileo was not the first to use a telescope, but he helped make it famous.

3. Electromagnetic radiation • Electromagnetic radiation is a form of energy that can travel through space in the form of waves. Visible light is an example of electromagnetic radiation. • Other forms: radio, infrared, ultraviolet, x-rays, gamma (listed from long wavelength to short wavelength) • Wait, what’s a wavelength???

4. http://www.youtube.com/watch?v=snNwE6txxP0

5. Electromagnetic spectrum • Wavelength – distance between the crest (high point) of a wave and the crest of the next wave • Spectrum – range of light colors with different wavelengths • Radio, infrared, visible light, ultraviolet, x-rays, gamma • ROYGBIV • What kinds of radiation do you experience every day?

6. Types of telescopes • Telescopes are instruments that collect and focus light and other forms of electromagnetic radiation. • Optical telescopes – telescope that uses lenses or mirrors to collect and focus visible light • Two major kinds: refracting and reflecting

7. Refracting telescopes • Uses convex lens to gather and focus light • Convex lens is a piece of transparent glass, curved so that the middle is thicker than the edges • Light enters the telescope through a large objective lens at the top. It focuses the light at a certain distance (focal length). The larger the lens, the more light collected. • The smaller lens at the lower end of the telescope is the eyepiece lens. It magnifies the image produced by the objective lens.

8. Reflecting telescope • Uses a curved mirror to collect and focus light. The curved mirror in a reflecting telescope focuses a large amount of light into a small area (just like the refracting telescope). • The largest telescopes are all reflecting telescopes.

9. Radio telescope • Used to detect radio waves from objects in space. Most have curved, reflecting surfaces. They focus radio waves the same way a mirror focuses light waves. The larger it is, the more waves it can collect.

10. Other telescopes • Can detect infrared, uv, x rays, gamma rays • Many large optical telescopes are equipped with systems that improve the quality of the images. They use computers and lasers.

11. Observatories • Observatories are buildings that contain one or more telescopes. • Many are located on mountains or in space. • Earth’s atmosphere makes stuff in space look blurry, so putting an optical telescope on a mountaintop eliminates some light from the cities and the sky is clearer. • Radio telescopes do not need to be put on mountaintops.

12. Telescopes in space • Hubble Space Telescope is a reflecting telescope with a mirror 2.4 meters in diameter (big big big). It orbits Earth above the atmosphere, so it can produce very detailed images. • Hottest objects in space give off x rays. Some telescopes pick these up, like the Chandra X ray observatory. • 2003 – NASA launched Spitzer Space Telescope – measures infrared.