Talk:List of most massive black holes/workpage



This is a list of the most massive black holes so far discovered (and probable candidates), ordered by mass. The unit of measurement used is the mass of the Sun (approximately $1.99 kilograms$).

Overview
A supermassive black hole (SMBH) is an extremely large black hole, on the order of 100,000 to 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. 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. Supermassive boson star

There is extreme difficulty in determining the mass of a particular SMBH, and so they still remain in the field of open research. SMBHs with accurate masses are limited only to galaxies within the Laniakea Supercluster and to active galactic nuclei. Another problem for this list is the method used in determining the mass. Such methods, such as broad emission-line reverberation mapping (BLRM), Doppler measurements, velocity dispersion, and the aforementioned M–sigma relation have not yet been well established. Most of the time, the masses derived from the given methods contradict each other's values.

Although SMBHs are currently theorized to exist in almost all massive galaxies, more massive black holes above, dubbed as 'ultramassive' ('UMBHs'), are rare; with only a handful of these black holes having been discovered to date.

This is the maximum mass of a black hole that models predict, at least for luminous accreting SMBH's. Given the age of the universe and the composition of available matter, there is simply not enough time to grow black holes larger than this mass. At around $1$, both effects of intense radiation and star formation in the accretion disc slows down black hole growth. New discoveries suggest that many black holes, dubbed 'stupendously large' ('SLABs'), may exceed or even, and would have been seeded by primordial black holes.



Radius
Per the no-hair theorem, the radius of a black hole depends directly on three quantities: the mass, angular momentum, and electric charge. The Schwarzschild radius is a characteristic radius proportional to the mass of an object that corresponds to the radius defining the surface for a Schwarzschild black hole (static, non-rotating and uncharged), in which any object whose radius is smaller than its Schwarzschild radius become a black hole. The surface at the radius acts as the event horizon of the black hole. Rotating or charged black holes (Kerr, Reissner–Nordström, Kerr–Newman) have two event horizons; the outer horizon is referred to the event horizon and the inner horizon is referred to the cauchy horizon. The more the black hole spins and/or has a higher electric charge, the smaller the event horizon is until close to twice smaller than the Schwarszchild radius. Surpassing the upper limit given for the spin parameter or the electric charge would cause two merged event horizons to shrink toward the singularity, resulting a naked singularity obeservable from the outside universe. This is expected theoretically they are unlikely to exist; however, there are potential exceptions such as B3 1715+425, which is believed to be a nearly naked rotating black hole.

Due to their extreme amount of gravity, light rays passing near extremely compact objects likes black holes or "ultracompact" neutron stars are deflected by their strong gravitational field that they can bend their path and magnify background images. This would leave a shadow (often encircled by a bright light ring), which is a boundary 1.5 times the Schwarzschild radius of the object where light can no longer orbit the object multiple times without being eventually captured. As such, the object would appear larger than its surface radius.

For more context regarding radii of black holes depending on their masses, spin parameters, and presence of electric charges, see section Black hole.

List
This list contains supermassive black holes with masses ($5$) or above, determined at least to the order of magnitude. Note that this list is very far from complete, as the Sloan Digital Sky Survey (SDSS) alone detected $200,000$ quasars, which likely may be the homes of billion-solar-mass black holes. Due to the very large numbers involved, listed black holes here have their mass values in scientific notation (numbers multiplied to powers of 10). Values with uncertainties are written in parentheses when possible. Note that different entries in this list have different methods and systematics in obtaining their mass values, and hence different levels of confidence in their masses. These methods are specified in their notes.

The radii of the event horzion of all black holes included within the list are based on both the mass and dimensionless spin parameter. Electric charge parameters are excluded from the list as it has been expected that the universe appear to be electrically balanced (or nearly so), thus it is likely that no black hole with a significant electric charge can naturally exist. Any black hole that does not have any measured spin paramater in the list is assumed as non-rotating, hence listed with the Schwarzschild radius based on its measured mass.

Listed below are some notable black holes under five billion solar masses, for the purpose of comparison.