List of most massive black holes

This is an ordered list of the most massive black holes so far discovered (and probable candidates), measured in units of solar masses (M☉), about 2×1030 kilograms.

Introduction

A supermassive black hole (SMBH) is an extremely large black hole, on the order of at least hundreds of thousands of solar masses (M☉), and is theorized to exist in the center of almost all massive galaxies. In some galaxies, there are even binary systems of SMBHs (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) speed 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 speed is flat, or even falling, toward the center, making it impossible to state with certainty that an SMBH is there. Nevertheless, it is commonly accepted that the center of nearly every galaxy contains a supermassive black hole. 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.

Though SMBHs are currently theorized to exist in almost all massive galaxies, more massive black holes are rare; only fewer than several dozen are known to date.