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Are
a collection of gas, dust and stars.
The distance across them is usually very
great and can be many light-years. For example, our Galaxy is made up of over
100 billion stars. The Sun is just one of them. Our Galaxy is over 100,000
light-years across and 3,000 light-years deep. Our Sun is about 30,000
light-years from the center of our Galaxy.
It is estimated that there are billions
of other galaxies in the universe.
The Milky Way is the band of light that
is produced by the thousands of stars that lie in the main section of our
Galaxy.
Are divided into types. Spiral,
ellipitical, lenticular, and irregular are the major types. We are part of a
spiral galaxy.
The photograph at the top is an example
of a distant spiral galaxy named M100.