TOPIC:

The Black Hole Theory

Miracle or science

Prepared By: Uzair Aman Khan

CONTENTS:

Introduction Historical Background Structure Of Black Holes Types Of Black Holes Light Behavior Near Black Holes Facts About Black Holes Milky Way Galaxy Famous Black Holes Formation And Growth Of Black Holes Stephen William Hawking’s Theory How To Locate Black Holes Controversy About Black Holes

INTRODUCTION:

Black holes are among the strangest things in the universe. They are massive objects with gravity so strong that nothing can escape, not even light.

They are called black holes because even light cannot pass or reflect from them and they absorb all the light hitting them.

HISTORICAL BACKGROUND: The idea of a body so massive that even light cannot escape from it was put

forwarded by a geologist John Michel in a letter written to Henry Cavendish in 1783 to the Royal Society.

In 1939, American physist Robert Oppenheimer developed a possible explanation for the these points of infinite density.

These theories remained a mathematical curiosity until the first black hole was found in 1964.

In 2006, Stephen Hawking proposed that microscopic black holes are formed in the huge explosion that gave birth to universes.

STRUCTURE OF BLACK HOLES: Singularity:

The point where whole mass of a black hole is concentrated. Photon Sphere:

The outer edge where light bends but is still escapable. Event Horizon:

It is a “point of no return” around a black hole. Accretion Disk:

It is a disk of gases, dust, stars and planets that fall into the orbit of a black hole.

TYPES OF BLACK HOLES: Stellar-mass Black Holes:

Stellar-mass black holes are created when massive stars explode, leaving behind a black hole with the mass of just a few suns.

Supermassive Black Holes:Supermassive black holes exist in the hearts of galaxies and usually

contain the mass equivalent to millions and billions of suns.

Intermediate Black Holes: Such bodies could form when stars collide in a chain reactions and

usually contain the mass equivalent to hundreds and thousands of suns.

THE FINITE SPEED OF LIGHT: As you all know (especially Contemporary people), That the speed of

light is a finite value in a vacuum. But when an object enters the event horizon of a black hole then it

have to move with speed more than light. In order to gain speed more than speed of light infinite amount of force

is needed. In all this universe there is no source of infinite force. Therefore, the fallen objects never return.

GENERAL RELATIVITY: WARPED SPACE:

LIGHT “BENDS”

GRAVITY BENDS THE PATH OF LIGHT:

FACTS ABOUT BLACK HOLES: The massive gravitational influence of a black hole bends space time in the

near neighborhood. The closer you get to a black hole, the slower time runs. Material that gets too close to a black hole gets sucked in and can never

escape. Black holes do not emit radiation on their own. They are detected by the radiation given off as material is heated in the

accretion disk. Their detection is also possible by the black hole’s gravitational effect on

other nearby objects or light passing by.

THE MILKY WAY GALAXY: The Milky Way Galaxy is our home galaxy in the universe. The Milky Way began forming around 12 billion years ago and is part of a group of about 50

galaxies called the Local Group which itself is part of a larger gathering of galaxies called the Virgo Super cluster of galaxies.

The Milky Way moves through space at a velocity of about 552 kilometers per second. 100-400 billion stars are present in this galaxy. Its galactic center is located about 26,000 light-years from Earth. At the center of Milky Way Galaxy lies a super massive black hole named as Sagittarius A*. This black hole contains the mass of about 4.3 million suns. The Milky Way contains a few hundred million stellar black holes. The speed of stars, gases and dust in accretion disk of this black hole is 220 kilometers per

second.

MILKY WAY CENTER: VISIBLE LIGHT VIEW:

The heart of our galaxy is a veritable soup of stars, gas, and dust. On a clear night in a dark sky, the view is breathtaking.

MILKY WAY CENTER: X-RAY LIGHT VIEW:

Lurking within our galaxy’s hot, turbulent center are x-ray binaries, neutron stars, and even a supermassive black hole.

FAMOUS BLACK HOLES: Cygnus X-1

Sagittarius A*

M87

Centaurus A

FORMATION AND GROWTH OF BLACK HOLES: When a star of mass more than 3 times

mass of the sun reaches to an end of its life, it gets crushed in its own gravity leaving behind a compact black hole.

Once a black hole has formed, it can continue to grow by absorbing additional matter like gases and dust from surrounding to become heavier and larger.

Large black holes are formed by the combination of small black holes and also when small black holes absorb huge stars.

STEPHENS WILLIAM HAWKING’S THEORY: Stephen Hawking’s great discovery

was that the mysterious regions in space we call black holes radiate heat.

Hawking said that these holes glow like a hot body and smaller they are, the more they glow.

Stephen Hawking’s theory says that the temperature of a black hole varies inversely to its mass.

RADIO JETS FROM BLACK HOLES:

Many black holes emit jets which moves nearly with the speed of light.

These jets are composed of electrons and positrons.

Magnetic field around black holes expels material and form these jets.

Interaction of jet materials with magnetic field gives rise to Radio emission.

HOW DO WE FIND BLACK HOLES: The X-rays are sent off into space and

when they strike the matter around the black hole , it can be detected.

Binary X-ray sources are placed to find strong black hole .

Another sign of the presence of a black hole is random variation of emitted X-rays. And gravitational lensing ,accretion disks and gas jets .

gravitational lensing

radiation emission

X-RAY BINARY: X-RAY LIGHT VIEW:

More dramatically, matter being pulled off the orbiting star, into the accretion disk of the black hole, glows brightly in x-rays.

CONTROVERSY ABOUT BLACK HOLE: “There is no escape from a black hole in

classical theory,” Hawking told Nature. Quantum theory, however, “enables energy

and information to escape from a black hole”. A full explanation of the process, the physicist

admits, would require a theory that successfully merges gravity with the other fundamental forces of nature.

But that is a goal that has eluded physicists for nearly a century. “The correct treatment,” Hawking says, “remains a mystery.”