This document discusses black holes and their properties. It begins with an introduction to black holes and their structure, including their singularity, event horizon, and accretion disks. It then covers different types of black holes like stellar-mass and supermassive black holes. The document discusses how light behaves near black holes and facts about them. Specific black holes like Sagittarius A* and Cygnus X-1 are mentioned. The formation and growth of black holes over time is summarized. Stephen Hawking's theory about black hole radiation is briefly outlined. The document concludes by discussing how astronomers locate black holes and the ongoing controversy around whether information can escape from black holes.

1. TOPIC:
The Black Hole
Theory
Miracle or science
Prepared By: Uzair Aman Khan

2. 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

3. 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.

4. 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.

5. 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.

6. 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.

7. 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.

9. GENERAL RELATIVITY: WARPED SPACE:

10. LIGHT “BENDS”

11. GRAVITY BENDS THE PATH OF LIGHT:

12. 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.

13. 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.

14. 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.

15. 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.

16. FAMOUS BLACK HOLES:
 Cygnus X-1
 Sagittarius A*
 M87
 Centaurus A

17. 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.

18. 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.

19. 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.

20. 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 .

22. 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.

23. 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.”