Galaxies
Galaxies are like island Universes. Their gravity holds in the stars that we see in the night sky. Our galaxy is called the Milky Way. One of the closest spiral galaxies to the Milky Way is Andromeda. The Milky Way is a spiral galaxy.
There are three different kinds of galaxies spiral, eliptical, and irregular.
Two large galaxies orbit the Milky Way called the Magellanic Clouds. It takes 1.5 billion years for them to complete an orbit. The closest one is the Large Magellanic Cloud wich is 160,000 light years away, and is less than one twentieth the size so it is to small to grow spiral arms. The Small Magellanic Cloud is slowly being ripped apart by our galaxy and is 190,000 light years away.
A small amount of known galaxies stand out from the rest. Explosions in their cores shoot out huge streams of gas called quasars. They are called active galaxies. Their energy comes not from the light of the stars but from the heat generated by large black holes near their center.
