Kamalov Daniiar

Black Holes

IntroductionHistory of Ideas about Black HolesFormationCharacteristics of BHGrowth of BHSize and AmountConclusion

Content

- Termin “black hole” was introduced by Jonhn Wheeler in 1967.

- Black hole - a region in the space where the gravitational pull is so strong that neither substance nor light can leave this area.

- Around a black hole there is a surface called an event horizon that marks the point of no return.

Introduction

In the 18th century John Michell and Pierre-Simon Laplace first mentioned about the objects with a huge gravitation, from which even light cannot escape.

In 1915 Albert Einstein developed the theory of general relativity.

Karl Schwarzschild finds black holes as a solution to Einstein’s equations (1916)

Robert Oppenheimer and Hartland Snyder predict that massive stars can collapse into black holes (1939)

History of Ideas

There are so many theories about formationThe most obvious way of black hole - the core

collapse of massive stars at least with the size of three solar masses. M= 1.989 × 10^30 kg. When the stars reaches its end of life, gets crushed under its own gravity, leaving behind a black hole.

When a gigantic star reaches the final stage of its life and is about to go supernova, it spends all the nuclear fuel by then. So it stops burning and heating up and cannot create the nuclear  energy required to feed the star.

Formation

Although black holes come in a variety of masses and sizes, their structures are all alike. A black hole's entire mass is concentrated in an almost infinitely small and dense point called a singularity. This point is surrounded by the event horizon . And a rotating black hole is surrounded by the ergosphere, a region in which the black hole drags space itself.

Characteristics

Once a black hole has formed, it can continue to grow by absorbing additional matter. Any black hole will continually absorb gas and interstellar dust from its direct surroundings and omnipresent cosmic background radiation.

Another possibility is for a black hole to merge with other objects such as stars or even other black holes

Growth of Black Hole

There is no limit to how large a black hole can be. However, the largest black holes we think are in existence are at the centers of many galaxies, and have masses equivalent to about a billion suns (i.e., a billion solar masses). Their radii would be a considerable fraction of the radius of our solar system.

The size of a black hole is defined by its mass. For a given mass, there is a length called the Schwarzschild radius, which is proportional to the mass.

How big can a Black Hole get?

There are so many black holes in the Universe that it is impossible to count them.

The Milky Way galaxy contains some 100 billion stars. Roughly one out of every thousand stars that form is massive enough to become a black hole. The nearest one is some 1,600 light years from Earth. (1 ly=2.9 x 10^13 m)

The most massive known black hole in the universe has been discovered on 10 January 2008 by David Shiga.

The black hole is about six times as massive as the previous record holder and in fact weighs as much as a small galaxy.

How many black holes are known to man that are in the universe?

Из Вселенной во Вселенную http://modcos.com/articles.php?id=44

Черная дыра существует? http://www.ng.ru/science/2009-01-28/9_blackhole.html

Black Hole http://en.wikipedia.org/wiki/Black_hole#General_relativity

Reference

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