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is an observed change in the frequency of a wave when the source or observer is moving
If a galaxy is moving toward Earth, the light we receive will seem compressed to shorter wavelengths. This change is called a _______.
If a galaxy is moving away from Earth, the light we receive will seem stretched to longer wavelengths. This change is called a _______.
Types of Galaxies
Spiral, Elliptical,and Irregular.
a galaxy having a spiral structure and arms that spiral out contain young bright stars
a galaxy shaped like a round or flattened ball, generally containing only old stars.
has an undefined shape and contains lots of young stars, dust, and gas.
Super-massive Black Hole
largest type in a galaxy; most if not all galaxies are thought to contain one at its center
An unusually bright object found in the remote areas of the universe. Quasars release incredible amounts of energy and are among the oldest and farthest objects in the known universe. They may be the nuclei of ancient, active galaxies.