Chapter 21 Stars, Galaxies, and the Universe
Introduction


How do we study other stars in our
galaxy if they are so far away?
We study the radiation that stars
emit to find out more about them.
 Energy that can travel through space
Electrois called electromagnetic radiation.
magnetic
Spectrum  Electromagnetic radiation can travel

through empty space and travels in
waves.
Electromagnetic radiation travels the
speed of light.
Electromagnetic
Spectrum
Picture From: http://www.astronomynotes.com/light/s3.htm
 The electromagnetic spectrum is
Electrothe full range of wavelengths of
magnetic
Spectrum
electromagnetic radiation.
Diagram From: saturn.jpl.nasa.gov/mission/nav-uplink.cfm
Diagram From: http://zebu.uoregon.edu/~imamura/122/images/electromagnetic-spectrum.jpg
RADIO WAVES
Electromagnetic  Longest waves and less frequent
Spectrum
than other waves.



Used for communication.
Radio telescopes used to collect
radio waves.
Size of wave ranges from the size of
a football field to the size of a
football.
MICROWAVES
Electromagnetic  Used in communication, weather
Spectrum
maps, and as a heat source.

Size of wave ranges from 1 foot to 1
centimeter.
INFRARED WAVES
Electromagnetic  Used as a source of heat.
Spectrum  Infrared telescopes used to detect

infrared waves.
Size of wave ranges from a few
centimeters to a few millimeters.
VISIBLE LIGHT
Electromagnetic  Only energy we can see with the
Spectrum
naked eye.


Refracting and reflecting telescopes
use visible light.
Size of wave is microscopic.
VISIBLE LIGHT
Electromagnetic  White light can be separated into the
Spectrum
7 different colors of light.
 ROYGBIV
 Red, Orange, Yellow, Green, Blue,
Indigo, Violet

Spectroscopes used to break white
light down into different colors.
ULTRAVIOLET WAVES
Electromagnetic  Energy that is partially blocked by
Spectrum
our atmosphere.




Common uses are tanning beds,
disinfection, and black lights.
A large amount of UV light is harmful
for living things.
UV cameras and telescopes use UV
rays.
Size of wave is a few molecules.
X-RAYS
Electromagnetic  Atmosphere reflects all X-rays back
into space.
Spectrum




Commonly used to take pictures of
bones.
Very harmful to living things.
X-ray telescopes use X-rays.
Size of wave is one molecule.
GAMMA WAVES
Electromagnetic  Shortest wave with the most energy.
Spectrum  Atmosphere blocks all gamma rays




from entering.
Deadly to living things.
Used for medical treatment.
Gamma telescopes study deep
space, black holes, stars, etc.
Size of wave is smaller than an atom.
Telescopes


Most telescopes collect and focus
different types of electromagnetic
radiation.
Two main types of telescopes:
reflecting and refracting telescopes.
 Refracting telescopes use lenses that
bend light to focus onto a small area.
 Reflecting telescopes use mirrors
instead of lenses but still focuses light
onto a small area.
The Keck Telescopes: Located in Mauna Kea, Hawaii
Hale 200-inch Reflector: Located in Mt. Palomar, California
Observat-  A building that contains one or more
telescopes is an observatory.
ories

Most observatories are on
mountaintops where images are less
blurred because of the Earth’s
atmosphere.
A giant telescope relies on multiple dishes - Located in
Socorro, New Mexico
Satellites



The shorter electromagnetic
radiation is blocked by the Earth’s
atmosphere.
Telescopes are placed on satellites to
detect these short, high energy
waves.
Hubble Space Telescope – reflecting
telescope that detects visible light,
infrared, and UV radiation.
Hubble Space Telescope
Compton Gamma Ray Observatory
Chandra X-ray Observatory
A telescope penetrates space with X-ray vision
Spitzer Space Telescope
It will spend 2 ½ to 5 years studying infrared light.
Spectrographs



Most large telescopes have
spectrographs.
A spectrograph breaks the light up
into colors.
Spectrographs reveal information
about stars like their composition
and temperatures.
Electromagnetic Spectrum Video Clip:
http://lgfl.skoool.co.uk/keystage4.aspx?id=318
Electromagnetic Spectrum Video Clip