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The Question
(Submitted March 17, 1998)
How large is the Milky Way?
The Answer
The disk of the Milky Way galaxy is about 100,000 light years in
diameter (one light year is about 9.5 x 1015 meters), but only
about 1000 light years thick.
Our Galaxy contains about 200 billion stars. Most of the stars are located
in the disk of our galaxy, which is the site of most of the star formation
because it contains lots of gas and dust.
The halo, which is a spherical cloud surrounding the disk, contains only
about 2% as many stars as the disk. It contains old and cool stars, since
it has little gas and dust.
Eric Christian and Samar Safi-Harb
for Ask a High-Energy Astronomer
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