"Black holes are where God divided by zero" - Albert Einstein Black hole – A region in the space where the gravitational pull is so strong that neither substance nor light can leave this area.

2. The Seekers

5. Introduction
 Terminology “black hole” was introduced by John 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.

6. History of Ideas
 In the 18th century JohnMichelle and Pierre-SimonLaplace mentioned
about the objects with a huge gravitation, from which even light cannot escape.
 In 1915 AlbertEinstein developed the theory of general relativity.
 KarlSchwarzschild finds black holes asa solution to Einstein’sequations
(1916).
 RobertOppenheimer andHartland Snyderpredict that massive stars can
collapse into black holes (1939).

7. What Are Black Holes?
 A black hole is a great amount of matter packed in a very small
area
such a big gravitational field, that nothing, not even light can escape
 can’t directly be observed - only way to perceive them is by
detecting their effect on other matter nearby
 attracted matter accelerates & heats up - emits x-rays that radiate
into space, emitting powerful gamma rays bursts - devour nearby
stars.

8. Formation
 many theories about formation
 The most obvious way of black hole - the core collapse of massive stars (Mass >= 3
x mass of sun).
 a gigantic star reaches final stage of its life - about to go supernova - spends all
the nuclear fuel by then
 stops burning and heating up - cannot create the nuclear energy required to feed
the star
 gets crushed under its own gravity, leaving behind a black hole.

9. Gravity deforms Space
Time

10. Gravity Bends The Path Of
Light

11. Types of Black
Holes
Miniature black holes:
 event horizons as small as atomic particles
Created during the Big Bang
compressed into a really small point -later exploded creating a massive explosion.
Super massive black holes:
Fast-moving gas jets and gravitational forces equal to 10 billion suns compressed
together
event horizon is an imaginary sphere around them
 When matter enters the black hole, it increases in size - reaching other matter which
it could not absorb before.

12. Types according to
physical properties
 The Schwarzschild black hole, which has no charge, or rotation,
the simplest type of black hole that exists.
The Reissner -Nordstrom black hole, which does not rotate, but
which has electrical charge.
The Kerr-Newman black hole, which has charge and rotates.
The Kerr black hole, which rotates and does not have charge inside.

13. White holes and
Wormholes
 White holes:
are not proved to exist
 considered to be the exact opposite of a black hole
 cannot absorb matter, it can only expulse
considered by some physicists to be the mathematical answer to the general
equations of relativity.
Wormholes:
 combination of a black hole and a wormhole
 would make matter enter through the black hole, and appear again
through the white hole
too close to each other, spaghettification would not happen.

15. Parts of a Black Hole
 The Singularity :
 allthe massoftheblackhole compressedinthis verysmallspace
 Singularity hasalmost infinite density
 The EventHorizon:
 defined as a big sphere surrounding the black hole
 absorbs any material includinglight
 Nothing can escape
 Sometheories saythat onlyradiation can escape thisarea

17.  The Accretion Disk:
 This is a disk that is composed by stellar material, which goes around
the black hole, forming a spiral.
 The Ergosphere:
 If a black hole is rotating, as it spins, its mass causes the space and time
to rotate around it.
 The Photon Sphere:
 place in which gravity is so high that photons have to travel around the
black holes´ orbit
 light is forced to stay inside the black hole here
 The Schwarzschild Radius:
 event horizon´s radius
 the escape velocity is equal to the speed of light at this radius

19.  Jets of Gas:
 suchhighintensitythat magneticfields areemitted perpendicular to theaccretion
disk
 somechargedparticles go aroundtheblack hole forming jets ofgases

20. Growth of a Black Hole
 Once formed, it can continue to grow by absorbing additional
matter
 will continually absorb gas and interstellar dust from its direct
surroundings and omnipresent cosmic background radiation.
 Another possibility - merges with other objects such as stars or
even other black holes

21. How Big Can A Black Hole Get?
 no limit to how large a black hole can be
 the largest black holes thought to be at the centers of many
galaxies - masses equivalent to about a billion suns – radii as
considerable fraction of radius of our solar system.
 size of a black hole - defined by its mass
 For a given mass - a length called the Schwarzschild radius
proportional to the mass.

22. Falling into a Black Hole
 Signals sent fromthe freely falling observerwould be time dilated and red shifted.
 Onceinside the event horizon,no communication with the universeoutside the event
horizonis possible.
 Butincoming signals from external world can enter.
 A black hole of massM has exactly the same gravitational field as an ordinary massM
at large distances.

23.  Fallingintoa black hole gravitationaltidal forces pull space-time in such a way that time
becomes infinitely long(as viewed by distant observer)
 fallingobserver sees ordinary free fall ina finite time

24. Spagettification

In Astrophysics, this term refers to the effect a black hole imposes on a body
or matter. The term was proposed by Stephen Hawkins in his book “A Brief
History of Time”, where he compared this effect to spaghettis, saying that
you are stretched, and you turn so thin that you break apart, and transform
into matter.

25.  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. 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 There In The
Universe?

27. Conclusion
 Individual modes may dominate the time evolution of some perturbation, and a
whole set of them could be usedto completely describethis time evolution.
 Whena black hole evaporates information is really gone.
 Due tothis thereis trouble in energyconservation.
 Invariancein time predictability.

28. Bibliography
 The following websites were consulted for relevant information :
 https://en.m.wikipedia.org/wiki/Black_hole
 https://www.slideshare.net/mobile/GarethJenkins6/black-hole-
presentation?qid=0be9e2dd-1af2-4e06-adf3-
64d4d28dc320&v=&b=&from_search=8
 https://www.nasa.gov/audience/forstudents/5-8/features/nasa-
knows/what-is-a-black-hole-58.html
 https://www.encyclopedia.com/science-and-technology/astronomy-
and-space-exploration/astonomy-general/black-hole

29. THANK YOU