by Merde Guadalope

Created on: April 05, 2009   Last Updated: April 09, 2011

Black holes are regions in space in which the gravitational field is extremely strong that not even light particles (photons) can escape it. There are four major types of black holes each one with its unique way of formation. The four types are stellar-mass black holes, micro black holes, Supermassive black holes and intermediate-mass black holes.

The most common type of black hole is the Stellar-mass black hole. The stellar-mass black hole is formed by the gravitational collapse of a massive star of about twenty solar masses or more. Once a massive star explodes in a violent explosion known as a supernova, it will subsequently form a neutron star; however, if the neutron star has a mass greater than five yellow dwarfs, the gravity will be so strong it will collapse in on itself into stellar-mass black hole.

Supermassive
black holes are usually found inside the centre of most galaxies. Although significantly larger than its three counterparts with solar masses of maybe 105 to 1010, it is distinctly weaker relative to its size. An astronaut inside the event horizon would not feel strong tidal forces until deep into the black hole because the central singularity (central black hole) is so far away from the horizon. A black hole of this magnitude is supposedly created by these theories that scientists have put forward. The first theory is that a stellar-mass black hole slowly accreting matter overtime would create a Supermassive black hole. The second theory put forward was that a large gas cloud would collapse into a relativistic star (unstable star) and being unstable as it is collapse into a black hole straight away without a supernova explosion. The third theory states that a dense stellar cluster could undergo core collapse and drive the internal velocity to relativistic speeds.

Another type of black hole is the Intermediate-mass black hole. However scientists are still unsure of how these black holes are formed as they are to massive to have been formed by a regular massive star gravitational collapse and are too small to have been formed by the intense density and velocity at the center of a galaxy the same way Supermassive black holes are formed. There are two prevailing theories however, as to how such a black hole can be formed. The first theory is that a stellar-mass black hole fusing with another compact object would result in an intermediate black hole. The second theory however states that the collision of two massive runaway stars and their subsequent gravitational collapse in a dense stellar cluster could lead to this type of black hole being formed.

Finally, the last type of black hole, the micro black hole is technically only hypothetical but it is a possibility. In principal, a black hole can be any size above the Planck mass but physicist Stephen Hawking argued that such black holes emit elementary particles such as photons and
gluons in a process known as hawking radiation. This process would undoubtedly make the black hole evaporate. Thus, the smaller the black hole the faster the evaporation. The creation of such a black hole would involve the concentration of matter or energy within the Schwarzschild radius, a feat that is technically impossible by today's technology. Such black holes would also possibly be able to be created during the early days of the universe.

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