Galaxy

The Milky Way galaxy has the shape of a flat disk, with a diameter of approximately 120,000 light-years. In the central region, the disk is a few thousand light-years thick, gradually thinning toward the edges, where it is about 1000 light-years thick. The Milky Way contains several hundred billion stars, numerous open and globular clusters, interstellar gas and dust, and perhaps even dark matter, a speculated form of matter. Our Solar System is located within this galaxy. At the center of the Milky Way lies a region known as the galactic bulge, which spans about 12,000 light-years in diameter. This is the galaxy's densest part and hides a supermassive black hole. Extending outward from the bulge are spiral arms, part of the structure known as the galactic bar, which give the galaxy its distinctive pinwheel-like appearance. Our Solar System, including the Sun and planets, is situated within one of these spiral arms, approximately 27,000 light-years from the galactic center. Surrounding the central disk is the galactic halo, a region with a diameter of about 200,000 light-years. This halo contains many ancient stars and numerous globular clusters.