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Distances
First Aid Cabinet
Distances are measured in two ways in astronomy. One is astronomical units (AU), which is mainly used when talking about distances within a solar system. The Earth is 1 AU away. Mars is about 1.5 AU's away, Jupiter is about 5 AU's away, and it starts getting farther back from there.
The other term used for measuring distance is light years. Light years are much longer than AU's and are used for measuring just about anything else. The nearest star, Proxima Centauri, is 4.35 light years away. We sit near the edge of the galaxy, around 75000 light years from the center.
Our galaxy is about 100,000 light years wide.
The nearest spiral galaxy, Andromeda, is about 2 million light years away.
The edge of the visible universe is about 13-15 billion light years away.
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