The Milky Way Galaxy contains over 200 billion stars and its largest neighboring galaxy is the Andromeda Galaxy. The oldest star in the Milky Way is nearly as old as the universe itself at 13.2 billion years. Gas and stars orbit the galactic center at around 220 kilometers per second, meaning the Solar System takes about 225 million years to complete one orbit of the Milky Way Galaxy. Gravitational forces exist between all masses in the universe.