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Facts on Galaxies

A galaxy is made up of an enormous number of stars, along with gases, dust particles, planets, moons and other assorted heavenly bodies held in place together by gravity. The Earth's solar system is part of the Milky Way galaxy.

Estimate
- According to the National Aeronautics and Space Administration website, researchers estimate that there are some 100 billion galaxies in the universe.
Size
- Galaxies considered as small have less than a billion stars while the larger galaxies contain over a trillion.
Visibility
- Three galaxies exist that an individual can see with the unaided eye, not counting the Milky Way. These are the Andromeda Galaxy, visible from the northern hemisphere, and the Large and Small Magellanic Clouds, visible from southern latitudes.
Types
- A spiral galaxy has arms like a pinwheel
  
  Astronomers classify galaxies by their shape, which results from the entire galaxy slowly rotating. A spiral galaxy appears to possess "arms" such as that of a pinwheel, an elliptical one is simply oval and an irregular galaxy has no discernable rotation and no special shape.
Distance
- In space, scientists measure the vast distances by light years---the distance light travels in a vacuum in one year's time, or 5.88 trillion miles. The closest galaxy to the Milky Way lies in the constellation Sagittarius and is 80,000 light years distant.

Astronomy