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 speedSpeed 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

http://hubblesite.org/

http://www.spitzer.caltech.edu/