Galaxies are large collections of stars, planets, asteroids, comets, and other space material like gases and dust. Stars are giant balls of gas in space. The stars are very hot! They can be up to 800,000°F! Our own Sun is also a star. It supplies us with light and heat. Stars take millions of years to form. Planets are rocky and gaseous objects. Galaxies are made up of millions of Solar Systems, just like ours! Galaxies are just a big soup of material that is clumped together. There are billions of galaxies in the universe. Galaxies are the key to forming planets and stars. The material in the galaxies creates the stars and planets. In the center of some galaxies, there are black holes. Black holes are depressions that suck everything around it’s event horizon, or edge inside. Black holes’ gravity keeps the galaxy’s structure and makes it spin. This is what a galaxy is!