There are four types of black holes and it all depends on their masses to differentiate them. The first type is called a primordial black hole. A primordial black hole is the smallest compared to the other three types of black holes. Since primordial black holes are only hypothetical, there are only theories about how they formed. It is widely believed that these primordial black holes formed very early in the Universe, soon after the Big Bang. An important factor in its formation is the fluctuation of the density of the Universe. Say no to plagiarism. Get a tailor-made essay on "Why Violent Video Games Shouldn't Be Banned"? Get an original essay The second type is called a stellar black hole. Stellar black holes have masses that can be up to 20 times greater than the mass of the sun. Initially, the core of a high-mass star will burn completely into iron. At this point energy production stops and the star's core rapidly collapses, causing a supernova explosion. If the star's core is greater than about 2-3 solar masses (the maximum mass of a neutron star), the neutron pressure will not be able to stop the collapse and, therefore, a stellar black hole will be created. The third type is called a supermassive black hole. These black holes can contain a million to a billion times more mass than a typical stellar black hole. There are only a handful of confirmed supermassive black holes as most of them are too far away to be observed. However, according to astronomers, there is a supermassive black hole at the center of the Milky Way. The name given to this black hole is “Sagittarius A*”. To put Sagittarius A*'s size into perspective, it has a mass equivalent to about 4 million suns. To date, there are only theories about how supermassive black holes form. Astronomers believe that once a black hole forms in the galaxy, it can grow by accretion of matter or merge with other black holes which in turn form a supermassive black hole. However, a prevailing theory is that supermassive black holes form from the collapse of massive gas clouds during the early stages of galaxy formation. Please note: this is just an example. Get a custom paper now from our expert writers Get a custom essay The last type is called an intermediate-mass black hole. Throughout history, astronomers have believed that black holes only come in two dimensions. The two are stellar black holes and supermassive black holes, as mentioned above. However, recent evidence from the Chandra X-ray Observatory, XMM-Newton (space X-ray observatory) and Hubble (space telescope) strengthens the case that medium-sized black holes exist. The first possible theory for the formation of intermediate-mass black holes (IMBHs) is that they form through the collapse of population III stars (the first generation of stars to form in the early stages of the universe). The second possible theory is that IMBHs are formed by the collision of massive stars or black holes within star clusters..