Information about black holes
| Black Hole Type | Description | Examples | Density | Average Solar Mass | Location | Detection |
|---|---|---|---|---|---|---|
| Stellar-mass Black Holes | a compact object formed from the gravitational collapse of a massive star (normally >8-20 solar masses) at the end of its life usually following a supernova explosion | Cygnus X-1, V616 Monocerotis (A0620-00), GRO J1655-40, LB-1, Gaia BH1, VFTS 243 | Stellar-mass black holes have incredibly high average densities, often exceeding 10¹⁶ kg/m³(trillions of times denser than water) for a 10M☉(10-solar-mass) object. | The average mass of a stellar black hole typically falls in the range of 5 to 10 times the mass of the Sun (5-10 M☉), with most ranging from 5 up to roughly 100 solar masses. | tellar black holes are scattered throughout galaxies, including the Milky Way, often found in binary systems with a companion star. There may be 100 million to a billion in our galaxy, with significant concentrations near the galactic center. Nearby examples include [Gaia BH1] (1,500 light-years) and [Gaia BH3] (2,000 light-years). | Stellar-mass black holes are detected by observing their gravitational influence on nearby stars, identifying X-ray emissions from superheated accretion disks, detecting gravitational waves during mergers via LIGO/Virgo, or using gravitational microlensing for isolated black holes. They are usually 3–20 solar masses, often found in binary systems. |
| Intermediate-mass Black Holes | Intermediate-mass black holes (IMBHs) are a rare class of black holes with masses ranging from 100 to 100,00 (or even up to 1 million) solar masses. | Omega Centauri (NGC 5139), HLX-1 (Hyper-Luminous X-ray Source 1), IRS 13E, GW190521, 3XMM J215022.4-0 55108, B023-G78, B023-G78 | The Average density of an Intermediate-mass black hole (IMBH), typically 10^2 to 10^5 solar masses, varies inversely with the squre of its mass, ranging from significantly deser than water (for 10^2 M☉) to roughly water density (for 10^5 M☉). | Intermediate-mass black holes (IMBHs) generally range from 10^2 to 10^5 solar masses (M☉), sitting between stellar-mass (< 100 M☉) and supermassive black holes (>10^5M☉). While theoretical, candidates often fall within hundreds to tens of thousands of solar masses, such as the 142M☉ object from GW190521 or potential detections in Omega Centauri (> 8,200 M☉) | IMBHs are generally located in the cores of dense globular clusters, the centers of dwarf galaxies, and in clsoe proxmity to supermassive black holes at the center of galaxies like the Milky Way. | Intermediate-mass black holes (IMBHs) are detected by observing their gravitational influence on surrounding stars in dense clusters, detecting gravitational waves from mergers, or identifying X-ray/radio emissions from accretion, often using tools like the Hubble and James Webb Space Telescopes. |
| Supermassive Black Holes | Supermassive black holes (SMBHs) are the largest type of black hole, containing millions to billions of solar masses (M ☉) at the centers of most galaxies. | Sagittarius A, M87, TON 618, Phoenix A, M31, NGC 7727, Holmberg 15A. | The average denisty of a (SMBHs) is inversely proportional to the square of its mass, meaning more massive SMBHs are less dense. While a stellar-mass black hole is extremely dense, an SMBH, such as M87* (6.5 X 10^9 M ☉), has an average density of =0.44 kg/m^3, which is less than that of air. | Supermassive black holes (SMBHs) typically range from roughly 10^5 to over 10^10 solar masses (M☉), with a common, representative average for those found in large galaxy centers being in range of millions to hundreds of millions (10^6-10^8) of M☉ While some reach tens of billions of solar masses, many large galaxy centers hold SMBHs in the 4-100 million M☉ range, such as Sagittarius A* at ~4 million M☉. | Supermassive black holes (SMBHs) are primarily located at the dynamic center of almost every large galaxy, including our own Milky Way. WHile the "standard" location is the galactic nucleus, recent simulations and observatios have revealed a significant population of "wandering" or off center SMBHs. | Supermassive Black Holes (SMBHs) are detected by oberserving their gravitational influence on nearby stars and gas, or by detecting the intense radiation emitted by material falling into them. |
| Ultramassive Black Holes | Ultramassive black holes (UMBHs) are the largest known black holes in the universe, possessing masses exeecding 10 billion solar masses | Ultramassive black holes (UMBHs) are monstes exceeding 10 billion solar masses (M☉) Key examples include TON 618 (~66 billion M☉), Phoenix A (~ 100 billion M☉), and Holm 15A (~ billion M☉). They are used to study galaxy evolution, often found in galactic centers using gravitational lensing and stellar kinematics, such as the 33-billion M☉ black hole Abell 1201 | Ultramassive black holes (UMBHs, > 5 X 10^9 M☉) have suprisingly low average densities often less than that of air or water, due to their immense Schwarzschild radii. For instance, a 3.8 X 10^9 M☉ black hole can have a density similar to air, while the UMBH in TON 618 has a density of roughly 4.23 g/cm^3, which is remarkablu low compared to stellar-mass black holes, which are denser than neutron stats. | Ultramassive black holes (UMBHs) generally have masses exceeding 10^10 (10 billion) solar masses (M☉). While defined as having a lower limit of roughly 10 billion M☉, observed UMBHs typically exist in the 10 to 60 billion M☉ range, with theoretical models suggesting they can reach up to 50 billion M☉. | Ultra-massive blacl holes (UMBHs), typically defined as exceeding 5 X 10^9 solar masses, are predominantly found at the centers of massive early-type galaxies and bright center (BCGs). They often reside in the center of dense galaxy clusters, acting as the anchor for the galaxy's structure. | Ultra-Massive Black Holes (UMBHs)—those exceeding 10 billion solar masses—are detected by observing their intense gravitational influence on surroundings, such as high-velocity stellar orbits, or through accretion disk radiation across X-ray, radio, and optical wavelengths. Advanced methods include analyzing high-J carbon monoxide (CO) emissions with ALMA, gravitational lensing, and detecting gravitational waves from mergers. |
| Quasars | Quasars (quasi-stellar radio sources) are the extremely luminous, energetic cores of distant young galaxies, powered by supermassive black holes feeding on surrounding matter. | 3C 273, Jo529-4351, TON 618, J0313-1806, Pōniuāʻena | Quasar surface density varies significantly by brightness, with typical sky surveys identifying roughly 1–2 quasars per square degree brighter than a magnitude of +18.0. Across the entire sky, this suggests around 10–13 million bright quasars, though densities can exceed 0.65 per square degree in clustered areas, compared to a general average of < 0.06 per square degree in sparser regions., Quasars are fueled by supermassive black holes, which are not intrinsically dense—their density is often comparable to water—but they are exceptionally compact, with high densities found only within their immediate singularities. | The average solar mass of a quasar (specifically its central supermassive black hole) typically range from 10^5 to 10^9 solar masses (M☉), with many commonly observed in the range of 100 million to over a billion solar masses. While some are smaller, large active quasasrs often exceed 10^9 M☉, growing rapidly in the early universe. | Quasars are primarily located at the center of distant, active galaxies, generally billions of light-years away. The vast majority are found at redshifts between z = 0.5 and z = 10.1,corresponding to distances of 600 million to over 30 billion light-years, with a peak density occurring when the universe was only 3.3 billion years old. | Most quasars are detected by searching for point-like, highly redshifted, and extremely luminous objects that appear "blue" or ultraviolet-bright across multiple filters. Astronomers identify them using large-scale sky surveys (e.g., SDSS, Gaia) and verify them through spectroscopy, often using machine learning to parse huge datasets for these rare, distant active galactic nuclei (AGN). |
| Active Galactic Nuclei | Active Galactic Nuclei (AGN) are incredibly luminous, compact regions at the centers of some galaxies, powered by supermassive black holes actively accreting matter. | 3C 273, PHL 1092, NGC 1068, NGC 4151. | Because Active Galactic Nuclei (AGN) are composite systems—consisting of a supermassive black hole (SMBH) and a surrounding accretion disk—there isn't a single "average density" for the entire region. Instead, astronomers calculate the "effective density" of the central engine itself. | Active Galactic Nuclei (AGN) do not have a single "average" mass because they span a vast range—from 10^6 to 10^10 solar masses (M☉). Instead, astronomers typically describe them by their characteristic ranges and the types of galaxies they inhabit. | AGNs are located at the exact centers of their host galaxies. Across the universe, they are found along the filaments of the cosmic web, typically in high-density regions like galaxy clusters. The highest concentration (the "average" distance) is roughly 10 billion light-years away at redshift z = 2. | Astronomers detect Active Galactic Nuclei (AGN) by observing their intense, non-stellar radiation across the entire electromagnetic spectrum. Because they are far more energetic than a typical galaxy core, they leave unique signatures that telescopes can pick up from billions of light-years away. |
| Primordial Black Holes | Primordial black holes (PBHs) are hypothetical black holes formed in the extremely high-density environment of the early universe, specifically within the first second after the Big Bang | As of April 2026, there are no confirmed examples of primordial black holes (PBHs), but astronomers have identified several compelling candidates and signals that point to their existence. | Unlike massive AGNs, primordial black holes are incredibly compact and dense. Because density is inversely proportional to mass squared, a PBH the size of an atomic nucleus could have the mass of a mountain. Their average density typically exceeds 10^19 kg/m³, making them far denser than neutron stars. Smaller PBHs formed in the high-pressure early universe are the densest objects theoretically possible. | Unlike AGNs, primordial black holes (PBHs) have no single average mass because they could have formed at any time in the early universe. Theoretically, they range from 10^-5 grams (Planck mass) to thousands of solar masses. However, most researchers focus on two "average" populations: asteroid-mass (10^-17 to 10^-12 M☉) as dark matter candidates, and sub-solar mass (0.1 to 1.0 M☉) recently detected by gravitational waves. | Because primordial black holes (PBHs) formed before galaxies existed, their "average" location is everywhere. They are theoretically distributed throughout the dark matter halos of galaxies. While many would drift in the empty cosmic voids, those near Earth would be orbiting within the Milky Way, potentially even passing through our solar system. | Astronomers detect primordial black holes primarily through gravitational microlensing, where their gravity briefly magnifies light from distant stars. Another key method is monitoring gravitational waves via detectors like LIGO, searching for "sub-solar" mergers—collisions of objects smaller than any star could produce. Additionally, we look for Hawking radiation (gamma-ray flashes from evaporating black holes) or dynamical disruptions, such as "invisible" objects pulling on binary star systems or affecting the movement of stars within galactic halos. |