Our solar system has been orbiting in our Milky Way since its formation about 4.5 billion years ago. How is this Milky Way structured, what holds it together and where is our solar system in it?

This lecture describes how astronomers study the structure and evolution of the Milky Way. The Milky Way is made up of stars, gas and elementary particles, and these components are in a very dynamic equilibrium. Since the formation of the universe, the Milky Way has grown and its structure and composition has evolved greatly. It will continue to change, and the distant future of our solar system may depend on it.