Īlthough SMBHs are currently theorized to exist in almost all massive galaxies, more massive black holes are rare with only fewer than several dozen having been discovered to date.

This correlation, although based on just a handful of galaxies, suggests to many astronomers a strong connection between the formation of the black hole and the galaxy itself. The reason for this assumption is the M–sigma relation, a tight (low scatter) relation between the mass of the hole in the ~10 galaxies with secure detections, and the velocity dispersion of the stars in the bulges of those galaxies. Nevertheless, it is commonly accepted that the center of nearly every galaxy contains a supermassive black hole. In all other galaxies observed to date, the rms velocities are flat, or even falling, toward the center, making it impossible to state with certainty that a supermassive black hole is present. In these galaxies, the mean square (or root mean square) velocities of the stars or gas rises as ~1/r near the center, indicating a central point mass. Unambiguous dynamical evidence for SMBHs exists only in a handful of galaxies these include the Milky Way, the Local Group galaxies M31 and M32, and a few galaxies beyond the Local Group, e.g.

In some galaxies, there are even binary systems of supermassive black holes, see the OJ 287 system. Comparisons of large and small black holes in galaxy OJ 287 to the Solar System.Ī supermassive black hole (SMBH) is an extremely large black hole, on the order of hundreds of thousands to billions of solar masses ( M ☉), and is theorized to exist in the center of almost all massive galaxies.

Massive blackhole