According to foreign media reports, how big is a black hole? A group of scientists believe that black holes can grow to what they call “extremely large” sizes, each weighing 100 billion or more solar masses. The discovery of such a huge black hole may reveal most of the properties of mysterious dark matter, the researchers said. These mysterious dark matter make up four fifths of the universe’s total matter. < / P > < p > most, if not all, galaxies have supermassive black holes at their centers, millions or billions of times the mass of our sun. At the center of our galaxy, for example, is Sagittarius A *, about 4.5 million solar masses. < / P > < p > the largest known black hole is the black hole inside the quasar ton 618, which is about 66 billion solar masses. With the huge ton 618, scientists can’t help but wonder whether there are still larger black holes, and whether there is an upper limit on the size of black holes. < / P > < p > in this new study, the researchers call 100 billion black holes of solar mass or above – larger than most currently seen – as “extremely large black holes” (slabs). Although the researchers also point out that there is no evidence to show that there are really extremely large black holes, they believe that there are supermassive black holes close to this size. < / P > < p > “surprisingly, very few people have paid attention to the existence of extremely large black holes, but they can theoretically exist,” said Florian Kuner, a theoretical cosmologist at the University of Munich and co-author of the study. < / P > < p > for extremely large black holes, a key question is, first of all, whether they can form. However, even for ordinary supermassive black holes, their formation has many unsolved mysteries. < p > < p > the traditional assumption is that when smaller black holes merge and swallow up the surrounding material, the galactic center will form a supermassive black hole. However, co-author Bernard Carr, a theoretical cosmologist at Queen Mary’s college, University of London, said previous studies had found that this model could not explain how black holes grew to very large masses when the universe was only a few billion years old? Karl explained that the key to another explanation of how ordinary supermassive black holes and possibly extremely huge black holes formed is the so-called “primitive black holes”. Previous studies have speculated that in less than a second after the big bang, random fluctuations in density in the hot, rapidly expanding new universe may gather enough material to collapse into a black hole. These primitive black holes may be the basis for the growth of larger black holes in the future. < / P > < p > If primitive black holes do exist, they may explain what dark matter is. Although people believe that there are a lot of dark matter in the universe, scientists still don’t know what this strange matter is made of, because no one has seen dark matter; at present, we can only study dark matter through its gravitational effect on normal matter. The nature of dark matter is currently one of the biggest mysteries in science. < / P > < p > “the question of whether intermediate mass primitive black holes can provide dark matter has aroused widespread interest,” said Luca weisinelli, a particle astrophysicist at the University of Amsterdam and co-author of the study. One of the ways to detect extremely large black holes is through gravitational lenses. According to Einstein’s general theory of relativity, the greater the mass of an object, the stronger the curvature of space-time around itself, and the stronger the gravity of the object. Gravity also bends light, so objects seen through strong gravitational fields, such as those produced by black holes, are lensed. The researchers say recent work has focused on finding gravitational lensing effects from smaller objects, but they say such research can also look for extremely large black holes. < / P > < p > another way to detect extremely large black holes is through their effects on their surroundings, such as gravitationally distorted galaxies. These black holes consume matter that astronomers can detect, and then produce heat, light and other radiation. In addition to the primitive black holes, another potential candidate for dark matter is the so-called wimp. If large mass weakly interacting particles exist, they will also be invisible and largely invisible. But previous studies have shown that if two weakly interacting particles collide, they annihilate each other and release gamma rays, providing an indirect way for scientists to detect their presence. Weisinelli said that the strong gravity of an extremely large black hole will gather a circle of weak interacting particles with large mass, and the high-energy gamma ray emitted by the annihilation of the massive weak interaction particles can help scientists find extremely large black holes. In short, Carr said, “we know that black holes exist in a variety of materials, so naturally we wonder if black holes have a natural upper limit. Some people may doubt the existence of extremely large black holes, because such huge black holes may not form. However, before the discovery, people had suspected the existence of medium and super massive black holes. We don’t know if the extremely large black holes really exist, but we hope our research will facilitate future discussions on this topic Global Tech