A planet is a part of a star system like 8 planets are part of the solar system. The solar system has one star - sun. A galaxy contains billions of stars. The solar system is part of Milky Way galaxy. There are billions of galaxies in the universe. Galaxies in a neighborhood form a group. Milky Way galaxy is a part of the Local group. Similar groups of galaxies form a cluster known as supercluster. The local group is part of Virgo supercluster.
