I. Chapter 24: Stars, Galaxies and the Universe
A. Tools of Modern Astronomy
1. ElectroMagnetic Radiation
a. Electromagnetic Radiation is energy that can travel directly through space
in the form of waves.
b. Parts of a wave:
wavelength
Crest
trough
c. EMR spectrum includes (in order from longest wavelength to shortest
wavelength) radio waves, infrared, visible light, ultraviolet, X-rays and gamma
rays.
d. Visible light waves in order from longest wavelength to shortest wavelength:
Red, Orange, Yellow, Green, Blue and Violet
2. Telescopes: collect and focus EMR
a. Visible Light Telescopes
i. Refracting Telescope: collects and focuses light using convex lenses
ii. Reflecting Telescope: uses a curved mirror to bounce the light onto a
small area
b. Radio Telescope: Uses a large parabolic dish to collect and focus radio waves
3. Spectrographs: break light into its visible components
a. Astronomers use spectrograths to determine temperatures and chemical
composition of the stars they are looking at.
B. Characteristics of Stars
1. Constellation: a group or pattern of stars in the night sky that appeared as symbols or
figures to ancient star gazers
a. Big Dipper, Orion, Gemini, Little Dipper, etc.
2. Distance units
a. AU – astronomical unit – distance from the Earth to our Sun, about 93 million
miles or 150 million kilometers
b. Light Year- distance light would travel in one year- a distance measurement,
not a time measurement!!- 9.5 million million kilometers!
3. Classifying stars: three characteristics used to classify stars: size, temperature
and brightness
a. Size:
i. Neutron star – about 20 kilometers in diameter
ii. White dwarf- about the diameter of the Earth
iii. Medium Size- about the size of our sun
iv. Red Giant- several times the diameter of our Sun
v. Super Red Giant – can be the diameter of our entire solar system
b. Surface Temperature: revealed by the star’s
color
i. Red - about 3,000 degrees Centigrade
ii. Yellow- about 6,000 degrees Centigrade
iii. White – about 10,000 degrees Centigrade
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, iv. Blue – about 50,000 degrees Centigrade
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