Milky Way

Our home galaxy: a barred spiral of several hundred billion stars about 100,000 light-years across, its disk seen from inside as the band of light crossing the night sky. The Solar System lies in the Orion Arm, about 27,000 light-years from the central supermassive black hole, Sagittarius A*, which it orbits roughly every 230 million years. A halo of globular clusters, dwarf satellite galaxies and dark matter surrounds the disk.