1. Astronomers use two main types of telescopes - refracting and reflecting telescopes - to observe visible light from space objects. 2. Refracting telescopes use lenses to gather and focus light, while reflecting telescopes use mirrors; the largest reflecting telescope has a main mirror 10 meters wide. 3. Telescopes face obstacles from Earth's atmosphere, so some are placed in space like the Hubble Space Telescope to overcome issues and allow clearer observation of faint objects in the universe.

1. 8 th Grade: Chapter 2 Lesson 2 Pgs. 68-74 For Student Use Only

2. Visible Light Light: Astronomers use the telescope to look at the world. There are 2 types of visible light telescopes: Refracting Telescope: Uses lenses to gather light and form an image Reflecting Telescope: uses lenses and mirrors to produce an image

3. Visible Light Refracting Telescope: It is made from a closed tube with an objective lens (large convex lens) at the top and an eyepiece (small convex lens) at the bottom. Objective lens- collects light, bends (refracts) rays of light Focal point- the point where light rays converge (meet) Eyepiece: magnifies the image and enlarges the picture

4. Visible Light Reflecting Telescope: Uses a large curved mirror in place of an objective lens Lenses refract different colors of light at different angles and makes it hard to keep images sharp; BUT, mirrors reflect colors at the same angle and produce a sharper image When parallel beam of light falls onto parabolic mirror, they reflect and are brought to focus at a point in front of the mirror.

5. Visible Light Reflection Telescopes: Largest Reflecting Telescope: 394 inch (10 meter) main mirror Located in Hawaii W. M. Keck Observatory

6. Visible Light Telescopes: Astronomers use telescopes and cameras. Use of camera help astronomers study the composition of stars. Certain gases allow certain colored light to pass through due to the make up of gas. Absorption Lines: dark lines that show which light has been absorbed.

7. Visible Light Light Spectrum: Spectroscope: a device that splits light into a spectrum for analysis Spectrograph: device used to study the spectra produced by the spectrascope These devices help scientists know what elements are in each stars

8. Visible Light Radio Astronomy: The weather often causes problems for optical telescopes. Clouds, smog, and haze can hinder view of the stars. Scientists use radio waves to also study stars. These can be studied rain or shine and can see things the eye cannot. Radio Telescope- instrument that collects radio waves from space.

9. Visible Light Radio Astronomy: The largest fully maneuverable radio telescope is in Germany Effelsberg telescope is 328 foot long Largest Stationary Radio Telescope: Built in a natural depression in the mountains of Puerto Rico. It is 1000 ft. across

10. Visible Light Singing Stars: Radio Telescopes let astronomers listen to stars (and the radio waves that it produces) Pulsars- are stars that produce rapid bursts of radio waves Revelations: Computer technology has helped astronomers study even more with Radio Astromomy.

11. Visible Light Radio Telescopes: Scientists have used radio telescopes to take pictures of Venus Radio telescopes have also helped to discover BLACK HOLES Black Hole: an object that is so massive and dense that that not even light is fast enough to escape from its surface.

12. Visible Light Overcoming Obstacles: Astronomers probing the heavens with visible light have always contended with several obstacles to their observations. Extreme Faintness of the light Earth’s atmosphere: Air currents make the stars twinkle, but ruin pictures.

13. Visible Light Overcoming Obstacles: NASA put a telescope above the thickest part of the atmosphere This was to overcome the shimmering of the stars Telescopes are put in space to help overcome obstacles. Hubble Space Telescope helps astronomers see into space