Sagittarius A* is the compact radio source and supermassive black hole at the center of the Milky Way. The Event Horizon Telescope resolved a bright 230 GHz ring around its shadow, while nearby S-stars reveal a mass of roughly 4.3 million Suns.
The Milky Way is a barred spiral galaxy containing 100–400 billion stars. Its central region contains the Galactic Center Group of fast-moving S-stars orbiting Sagittarius A*, the galaxy's supermassive black hole.
