Formation and Evolution Essay Example for Free

make-up and Evolution EssayA ominous clutter is a theoretical region of space in which the gravitational field is so force-outful that naught, not even electromagnetic radiation (e. g. visible light), fundament escape its pull after having fallen past its event horizon. Black holes are objects so arduous that not even light can escape their gravity, and since nothing can travel faster than light, nothing can escape from inside a threatening hole. On the other hand, a slow hole exerts the corresponding force on something far away from it as any other object of the same mass would. For example, if our Sun was magically crushed until it was round 1 mile in size, it would draw a sinister hole, but the Earth would remain in its same orbit. Even back in Isaac Newtons time, scientists speculated that such(prenominal) objects could exist, even though we now know they are more accurately described using superstars General Theory of Relativity. Using this theory, mordant ho les are fascinating objects where space and time become so warped that time practically draw a blanks in the vicinity of a black hole.The origin types fork up metrical masses ranging from 4 to 15 Suns, and are believed to be formed during supernova explosions. The after-effects are discovered in some X-ray binaries known as black hole candidates. On the other hand, galaxy-mass black holes are found in Active Galactic Nuclei (AGN). These are thought to have the mass of about 10 to 100 billion Suns. The mass of one of these super massive black holes has recently been measured using radio astronomy.X-ray observations of iron in the accretion disks may actually be covering the effects of such a massive black hole as well. Formation and Evolution The first formation process for black holes is expected to be the gravitational collapse of lowering objects such as stars, but there are also more exotic processes that can lead to the production of black holes. Gravitational collapse occurs when an objects internal pressure is insufficient to resist the objects own gravity.For stars this usually occurs either because a star has too tiny fuel left to maintain its temperature, or because a star which would have been stable receives a lot of extra matter in a way which does not get up its core temperature. In either case the stars temperature is no longer high enough to prevent it from collapsing chthonic its own weight. The result is one of the various types of compact star. Which type of compact star is formed depends on the mass of the remnant the matter left over after changes triggered by the collapse (such as supernova or pulsations leading to a planetary nebula) have blown away the outer layers.If the mass of the remnant exceeds 3-4 solar masses (the Tolman-Oppenheimer-Volkoff limit)either because the original star was very heavy or because the remnant collected superfluous mass through accretion of matter)even the degeneracy pressure of neutrons is ins ufficient to stop the collapse. After this no known mechanism (except maybe the quark degeneracy pressure, see quark star) is powerful enough to stop the collapse and the object will inevitably collapse to a black hole.This gravitational collapse of heavy stars is assumed to be responsible for the formation of around (if not all) stellar mass black holes. at once a black hole has formed, it can continue to grow by absorbing additional matter. some(prenominal) black hole will continually absorb interstellar dust from its direct surroundings and present cosmic background radiation, but neither of these processes should significantly affect the mass of a stellar black hole. Properties of Black Holes According to the No Hair theorem a black hole has lonesome(prenominal) three self-directed physical properties mass, aid and angulate urge.Any two black holes that share the same values for these properties are indistinguishable. This contrasts with other astrophysical objects such as stars, which have very numerouspossibly infinitely manyparameters. Consequently, a great deal of information is lost when a star collapses to form a black hole. Since in most physical theories information is preserved (in some sense), this loss of information in black holes is puzzling. Black Hole Types The simplest possible black hole is one that has mass but neither charge nor angular momentum.These black holes are often referred to as Schwarzschild black holes after the physicist Karl Schwarzschild who discovered this solution in 1915. It was the first (non-trivial) exact solution to the Einstein equations to be discovered, and according to Birkhoffs theorem, the only vacuum solution that is spherically symmetric. The Reissner-Nordstrom solution describes a black hole with electric charge, while the Kerr solution yields a rotating black hole. The most general known stationary black hole solution is the Kerr-Newman metric having both charge and angular momentum. SizesBlack hol es occurring in nature are commonly classified according to their mass, self-sufficient of angular momentum J. The size of a black hole, as determined by the radius of the event horizon, or Schwarzschild radius, is comparative to the mass through where is the Schwarzschild radius and is the mass of the Sun. Thus, size and mass have a simple relationship, which is independent of rotation. According to this mass/size criterion then, black holes are commonly classified as passing massive black holes, Intermediate-mass black holes, Stellar-mass black holes, Micro black holes ConclusionThere is very reliable evidence from astronomical observations that the universe is full of black holes with sizes ranging from six to a billion solar masses in size. Black hole accretion power is responsible for some of the most spectacular phenomena in the universe. These phenomena are NOT well understood, however, largely because of the complexity of the physics of the central accretion flow. There is little doubt, though, that black holes exist at the heart of active galactic nuclei, quasars, and certain X-ray binaries. Accretion power is an important contributor to the overall evolution and ecology of the universe.Electromagnetic observations are currently probing the inward parts of accretion flows, and revealing interesting effects of the relativistic space-time assuming our models of the flows are not WAY wrong. How can one prove the existence of black holes, short of a suicidal jumpstart across an event horizon? Detection of gravitational waves ripples in the fabric of space-time itself, is perhaps the only way. Currently astronomers mint black holes if they are lit up electromagnetically a very biased view Black holes which are lit up gravitationally may offer a very otherwise biased view. Works cited Kraus, Ute.Step by Step into a Black Hole. (2005-03-20) Remillard, Ronald A. McClintock, X-ray Properties of Black-Hole Binaries, Ann. Rev. Astron. Astrophys. (200 6) 44 4992. Celotti, A. Miller, J. C. Sciama, D. W. , Astrophysical evidence for the existence of black holes, (1999) Class. Quant. Grav. 16. Hawking, S. W. Penrose, R. , The Singularities of Gravitational Collapse and Cosmology, (1970) Proc. Roy. Soc. Lon 314 (1519) 529548 Schwarzschild, Karl , Uber das Gravitationsfeld eines Kugel aus inkompressibler Flussigkeit nach der Einsteinschen Theorie(1916), Sitzungsber. Preuss. Akad. D. Wiss. 424434.