Black holes

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  • Publicado : 19 de enero de 2010
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Black Holes

Index

1 Justification………………………………………………….….page 2
2 Introduction………………………………………………...…...page 2
3 Black holes…………………………………………………..….page 3
3.1 What is a black hole?........................................................page 3
3.2 How does black holes form?.............................................page 3
3.3 What is biggest blackhole?...............................................page 4
3.4 How many black holes are there?.....................................page 4
4 Conclusions……………………………………………………..page 5
5 BIgraphy…………………………………………………………page5

Justification
We are doing this work cause we want know more about the Black holes
This is some questions than we have and we want answer it-What is a black hole?
- how does black holes form ?
-what is the biggest black hole ?
- How many black holes are there?

Introduction
Astronomers have discovered quite a few objects that can only be explained as black holes. These objects are dark, so we cannot see them, but they exert a powerful influence on the stars, gas, and even spacearound them. These objects are so dark, dense, and heavy that they must be either black holes or something even more exotic.
A black hole is an object with such powerful gravity that nothing can escape from it, including light. The black hole's mass is concentrated in a point of almost infinite density called a singularity. At the singularity itself, gravity is almost infinitely strong, so itcrushes normal space-time out of existence. As the distance from the singularity increases, its gravitational influence lessens. At a certain distance, which depends on the singularity's mass, the speed needed to escape from the black hole equals the speed of light. This distance marks the black hole's "horizon," which is like its surface. Anything that passes through the horizon is trapped inside theblack hole. Black holes come in several varieties, depending on mass.

Black holes
Now we are going to answer the questions:

What is a black hole?
In general relativity, a black hole is a region of space in which the gravitational field is so powerful that nothing, including light, can escape its pull. The black hole has a one-way surface, calledan event horizon, into which objects can fall, but out of which nothing can come. It is called "black" because it absorbs all the light that hits it, reflecting nothing, just like a perfect blackbody in thermodynamics. Quantum analysis of black holes shows them to possess a temperature and radiate like black bodies.
Despite its invisible interior, a black hole can reveal its presence throughinteraction with other matter. A black hole can be inferred by tracking the movement of a group of stars that orbit a region in space which looks empty. Alternatively, one can see gas falling into a relatively small black hole, from a companion star. This gas spirals inward, heating up to very high temperature and emitting large amounts of radiation that can be detected from earthbound andearth-orbiting telescopes. Such observations have resulted in the general scientific consensus that, barring a breakdown in our understanding of nature, black holes do exist in our universe.
how does black holes form ?
A black hole forms when any object reaches a certain critical density, and its gravity causes it to collapse to an almost infinitely small pinpoint. Stellar-mass black holes form when amassive star can no longer produce energy in its core. With the radiation from its nuclear reactions to keep the star "puffed up," gravity causes the core to collapse. The star's outer layers may blast away into space, or they may fall into the black hole to make it heavier. Astronomers aren't certain how supermassive black holes form. They may form from the collapse of large clouds of gas, or from...
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