A galaxy is made up of stars, dust, and gas in space. Galaxies are so big that they seem endless. They are held together by gravity--the force that pulls things together. Billions of galaxies are scattered throughout the universe.

Image to left: Spiral galaxies are shaped like pinwheels, with bright arms that curl out from a bulge in the center. Credit: D. Hunter (Lowell Observatory) and Z. Levay (Space Telescope Science Institute)/NASA

The sun and all the planets that move around the sun, including Earth, are in a galaxy called the Milky Way. The Milky Way is called a spiral galaxy because it is spiral-shaped, like a pinwheel.

Only three galaxies outside the Milky Way can be seen from Earth without a telescope. These galaxies look like small, hazy patches of light. People north of the equator can see the Andromeda Galaxy. People south of the equator can see the galaxies called the Large Magellanic Cloud and the Small Magellanic Cloud.