to the
Solar System A
supermassive black hole (SMBH) is an extremely large
black hole, on the order of hundreds of thousands to tens of billions of
solar masses (), and is theorized to exist in the center of almost all massive
galaxies. In some galaxies, there are even binary systems of supermassive black holes (see the
OJ 287 system.) 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.
NGC 4395. 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. 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. 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. 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. and the other from Charles Nelson using [OIII]λ5007 value and velocity dispersion. Note that this list is very far from complete, as the
Sloan Digital Sky Survey (SDSS) alone detected
quasars, which likely may be the homes of billion-solar-mass black holes. In addition, there are several hundred citations for black hole measurements not yet included on this list. Despite this, the majority of well-known black holes above 1 billion are shown.
Messier galaxies with precisely known black holes are all included. New discoveries suggest that many black holes, dubbed 'stupendously large', may exceed . == List ==