Evolution of spiral galaxies. Our solar system is in a galaxy called the Milky Way. Scientists estimate that there are more than 100 billion galaxies scattered throughout the visible universe. Astronomers have photographed millions of them through telescopes. The most distant galaxies ever photographed are as far as 10 billion to 13 billion light-years away.
Small galaxies have fewer than a billion stars.
Large galaxies have more than a trillion. The Milky Way has a diameter of about 100,000 light-years. The solar system lies about 25,000 light-years from the center of the galaxy. There are about 100 billion stars in the Milky Way. Only three galaxies outside the Milky Way are visible with the unaided eye.