Chapter 19

 How…Telescopes:  What Scientists use to study objects in space.  Purpose of Telescope:  to gather & focus light from objects in space.

 Def: Range of RADIANT ENERGY (also called electromagnetic waves)  Arranged SHORT to LONG ex) gamma ex) Radio  Transfers (goes thru) matter & space  Examples:  Visible Light – kind we see.  Microwave – microwave oven; cell phone  Infrared – Remotes

 Stars emit all wave lengths!!  HOT stars = shorter waves ex) gamma  COOL stars = longer waves ex) radio or infrared  Sun = MED waves  ex) visible light  Planets & Moon – DO NOT emit light!!! *They reflect Sun’s light!!!!

 Waves travel at a constant speed Speed of Light = 300,000 km/s  Stars light takes billions / millions years to reach us ….  Sun’s light takes 8 minutes to reach us.  HOW scientists study the PAST by studying the stars

 A) OPTICAL – use visible light.  1) Refracting Telescope  Convex LENS  (Look thru the end. Use at night when clear skies.)  2) Reflecting Telescope  Concave MIRROR  (Look thru the side. Use at night when clear skies)  Advantage – Can make the mirror a lot bigger than a glass lens ( w/ out a flaw)

 B) RADIO Telescopes  Collect radio & microwaves (not a picture like a visible light)  Arranged in arrays – many together (These types of waves a LLLOOOOONNNNNNNGGG so need to be bigger.  Advantage over OPTICAL?  Can be used ANY time … day or night; weather doesn’t matter. *DISADVANTAGES – need a large empty area to put them - moisture harms them (why they are usually in dry areas)

 C) Problems w/ Telescopes on Earth  Weather issues  Atmosphere distorts what we see  Try to fix that w/ ADAPTIVE OPTICS (technology that adjusts the picture based on atmospheric conditions)

 D) Space Telescopes – this avoids the problems with …  Weather  Atmosphere  Light pollution  Advantages: darker; collect energy in diff. wave lengths  Ex) Hubble – visible light  Ex) Spitzer - Infrared