人馬座A
The Galactic Center is marked by an intense radio source named (pronounced "Sagittarius A-star"). The motion of material around the center indicates that Sagittarius A* harbors a massive, compact object. This concentration of mass is best explained as a supermassive black hole (SMBH) with an estimated mass of 4.1–4.5 million times the mass of the Sun. The rate of accretion of the SMBH is consistent with an inactive galactic nucleus, being estimated at around   per year. Observations indicate that there are SMBHs located near the center of most normal galaxies.