Galaxy

A galaxy is a group of stars, gas, and dust that move together in outer space. A galaxy is made up of billions of stars, just like our own Milky Way galaxy. In a galaxy, the stars are held together by their own gravity, which means they don't move away from each other. As far as we know, all galaxies contain a supermassive black hole at the center. This is a very large black hole that is so massive it bends space and time around it. In the night sky, we can usually only see one kind of galaxy -- our own Milky Way galaxy -- because it is so far away from other galaxies. Each galaxy is different in its size, shape, and the amount of stars and dust it holds.