A black hole is one of the most mysterious and fascinating objects in the universe. It is a region in space where gravity is so strong that nothing—not even light—can escape. This extreme gravitational pull is caused by an incredibly dense amount of mass compressed into a very small space. Because black holes do not emit light, they are invisible and can only be detected by their effects on surrounding matter and space-time. Black holes were first predicted by Albert Einstein’s General Theory of Relativity in 1915. However, the concept of an object with gravity so strong that even light cannot escape was first considered by John Michell in 1783 and later by Pierre-Simon Laplace in 1796. In 1967, physicist John Wheeler coined the term “black hole” to describe these objects.
Black holes are usually formed when massive stars collapse at the end of their life cycle. This process happens through a supernova explosion, where a dying star sheds its outer layers, and the core collapses due to its own gravity. If the remaining mass is more than about three times the Sun’s mass, no known force can stop the collapse, and a black hole forms. Over time, black holes can grow by merging with other black holes or by accumulating matter from their surroundings. There are also theories suggesting that black holes could have formed in the early universe right after the Big Bang. These hypothetical objects, called primordial black holes, could range from tiny microscopic sizes to large planetary masses. Following are the 5 largest black holes discovered so far.
1. Phoenix A* – The Largest Black Hole Ever Found (~100 Billion Solar Masses)
Phoenix A*, located in the Phoenix Cluster about 5.7 billion light-years away, is the largest known black hole with an estimated mass of 100 billion times the Sun. It far exceeds the previously believed upper limit of black hole sizes.
This ultramassive black hole sits at the heart of the Phoenix Cluster, which contains many galaxies. The Phoenix Cluster is known for its intense X-ray emissions, indicating a highly energetic environment likely influenced by Phoenix A*. Scientists previously thought that black holes could grow to around 50 billion solar masses, but Phoenix A* has shattered that assumption, suggesting a different evolutionary path.
How did it become so large? Black holes grow by accreting matter—gas, dust, stars, and even other black holes. Given its size, Phoenix A* likely went through a phase of rapid accretion in the early universe, feeding on an enormous amount of material over billions of years. Its discovery forces astronomers to reconsider black hole growth mechanisms, especially in dense galactic environments.
2. TON 618 – The Brightest and One of the Largest Known Black Holes (~40.7 Billion Solar Masses)
TON 618 is located 10.4 billion light-years away and has a mass of approximately 40.7 billion solar masses. It is an ultramassive black hole found in a quasar, meaning it actively feeds on surrounding material, producing extreme brightness.
Quasars are some of the most luminous objects in the universe, and TON 618 is one of the brightest, indicating that it has an extremely high accretion rate. Scientists estimate that TON 618’s accretion disk—the swirling mass of gas and debris falling into the black hole—is among the largest ever observed.
One reason why TON 618 is so massive is its early formation in the universe. Because it lies more than 10 billion light-years away, astronomers see it as it was when the universe was only a few billion years old. This suggests that some black holes reached enormous sizes relatively quickly, likely due to a combination of mergers with other black holes and continuous feeding on dense interstellar material.
3. Holmberg 15A – The Largest Black Hole Found Using Stellar Dynamics (~40 Billion Solar Masses)
Holmberg 15A is located in the center of the Holm 15A galaxy, about 700 million light-years away. This galaxy is a supergiant elliptical galaxy and is part of the Abell 85 galaxy cluster.
Scientists discovered Holmberg 15A’s black hole using stellar dynamics, meaning they calculated its mass based on how nearby stars move under its gravitational influence. Unlike quasars, which are identified by their brightness, Holmberg 15A’s black hole is relatively dormant, meaning it does not actively consume large amounts of matter.
Despite its inactivity, its gravitational influence extends over a vast region, suggesting it has accumulated mass over billions of years. This likely happened through galactic mergers, where multiple smaller black holes combined into one colossal object.
4. Abell 1201 BCG Black Hole – A Discovery Using Gravitational Lensing (~30 Billion Solar Masses)
Located in the Abell 1201 galaxy cluster, this black hole is about 30 billion times the Sun’s mass. Unlike other black holes discovered through X-ray emissions or stellar dynamics, this one was found using gravitational lensing.
Gravitational lensing occurs when a massive object, like a galaxy or black hole, bends light from objects behind it due to its immense gravitational pull. Astronomers used this effect to detect Abell 1201 BCG’s black hole when they noticed light from a distant background galaxy being distorted as it passed near the black hole.
This black hole is relatively inactive, meaning it is not consuming much material. Its discovery suggests that many more enormous black holes exist, but they remain hidden because they do not emit detectable radiation.
5. IC 1101 Black Hole – A Giant at the Center of a Massive Galaxy (~40 Billion Solar Masses)
IC 1101 is one of the largest known galaxies, and it hosts a black hole with an estimated mass of 40 billion solar masses. Located 1.04 billion light-years away, this galaxy is famous for being one of the brightest and largest elliptical galaxies ever found.
Like other supermassive black holes, IC 1101’s central black hole likely grew through accretion and mergers. Over billions of years, IC 1101 merged with other galaxies, adding to the size of both its central black hole and the galaxy itself.
IC 1101 is also interesting because it is part of a galaxy cluster environment, meaning its black hole might have grown from multiple interactions with smaller galaxies. Observations suggest that it has a massive accretion disk, although it is not as active as TON 618
