By combining information from long monitoring campaigns by NASA’s Chandra X-ray Observatory and ESA’s XMM-Newton, with observations by the Swift satellite, astronomers were able to carefully trace the activity of the Milky Way’s supermassive black hole over the last 15 years. The supermassive black hole — Sagittarius A* (Sgr A*) — weighs in at slightly more than 4 million times the mass of the Sun. X-rays are produced by hot gas flowing toward the black hole.