1.
The Black Holes
Presented by: Sarita Chauhan
M.Sc. (Final) Physics
Department of Physics G.C.A

2.
History
• 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)

3.
2
“Black
holes are exotic structures whose
gravitational fields are so powerful that they
trap everything, even light. They were first
postulated by Albert Einstein's theory of
general relativity.”
ss
much
ma
1
“A black hole is a region of space that has so much
mass concentrated in it that there is no way for a
nearby object to escape its gravitational pull.”
gravity
…no escape from
1. What is a black hole?

4.
Black holes
• This can happen when a star is dying.
• Though they are black they are invisible to us.
• The density of a black hole is so great it would be like
taking the whole Earth and crushing into a volume smaller
than a 1” marble!.

5.
on the basis of mass : Three classifications of
black holes
• Stellar-mass: 3 to 20 times the mass of our Sun
• Supermassive: Black holes with millions to billions of
times the mass of our Sun
• Mid-mass: In between stellar-mass and supermassive .

6.
Mid Mass
Supermassive
Stellar mass

7.
Formation of black holes
• The most common way for a black hole to form is
probably in a supernova, an exploding star.
• When a star of about 25 times the mass of the sun
ends its life, it explodes.
• The outer part of the star screams outward at high
speed, but the inner part of the star, i.e., core, collapses
down.

8.
Formation of black holes
• If there is enough mass, the gravity of collapsing core will
compress it so much that it can become a black hole. The
black hole will have a few times mass of the sun. this is
called a ‘stellar mass black hole’.
• But there are also monsters, called super massive black
holes. These are present in the centers of galaxies, and are
huge. They can be millions or billions of times the mass of
sun! these are probably formed during the formation of
galaxies. In milky way we are having sagittarius A* as our
supermassive black hole.

9.
5. DO ALL STARS BECOME STELLAR-MASS
BLACK HOLES?
Mass < 8 suns
Mass < 3 suns
Mass <1 sun
It all depends
on the amount
of mass stars
contain
Becomes
a white dwarf
http://www.nasa.gov/audience/forstudents/k-4/stories/what-is-a-black-hole-k4.html
Becomes
a neutron star
Becomes
a black hole

10.
Characteristics
• 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.

11.
Size of black holes
• The more massive a black hole is, the more
space it takes up. A typical 10-solar-mass black
hole would have a radius of 30 kilometers, and a
million-solar-mass black hole at the center of a
galaxy would have a radius of 3 million
kilometers.

12.
Parts of a Black Hole
Outer event
horizon
Space-time
Inner event
horizon
Singularity
“White hole”
Space-time- the fabric
of both space and time

13.
Outer Event Horizon &
Inner Event Horizon
• Outer event horizonthe point of no return.
• As one nears the outer
event horizon, it
appears time slows
down and stops
altogether.
• Objects start to travel at
the speed of light after
they reach the inner
event horizon

14.
Singularity
• Scientists believe that at
the center of a black hole
lies a gravitational
singularity, a point in the
space-time curvature
becomes infinite.
• The center of the black hole
is a point of infinite density
and zero volume, called a
singularity

15.
Different type of black holes…..
•
Schwarzchild black holes : Don’t rotate
and have no charge.
•
Reissner – Nordstrom black holes: don’t rotate
but have charge.

16.
•
Kerr black holes: rotate but have no charge.
•
Kerr – Newman black holes: Rotate and have charge.

17.
Growth of Black Hole
• 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 omit present cosmic background
radiation.
• Another possibility is for a black hole to merge with other
objects such as stars or even other black holes

18.
2. How do we
«see»
black holes?
Nobody has
literally seen a
black hole yet,
but there are
instruments with
which
astronomers
detect and study
their X-ray
emissions and
their effects over
matter.
SATELLITES DETECT
RADIATION
ATOMS EMIT X-RAYS INTO
SPACE
ATOMS ARE
IONIZED AND
REACH A FEW
MILLION KELVIN
THE BLACK HOLE MOVES
FASTER AND HEATS UP
MATTER
FALLS OR IS PULLED INTO
THE
BLACK HOLE
http://imagine.gsfc.nasa.gov/docs/science/know_12/black_holes.html

19.
How do we know it’s there?
Years
“Weird”
motions of
objects
nearby
supermassive black
Orbits of stars very close to the center of our
galaxy over a period of 14 years

20.
IF WE CAN’T SEE THEM, THEN HOW DO WE KNOW
THEY ARE THERE?
 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 n gas jets .

21.
Accretion Disk and Plasma Jets…..
•
•
•
•
An accretion disk is a spinning gas
and matter that
a black hole attracts.
Accretion disk converts matter into
energy very efficiently.
Viscosity in the disk redistributes
angular momentum, causing material
in the disc to spiral inward
towards the singularity.
Plasma jet is Relativistic jet that
is given off by the black holes.

22.
Where are black holes located?
• Black holes are everywhere.
• There are probably millions of black holes in milky way
alone, but the nearest one is discovered 1600
quadrillion Kms!
• The giant black hole in the center of the galaxy is even
farther away, at a distance 30,000 light years, we're in
no danger of sucked in to the vortex.

23.
Falling into a black hole
 The pulling force would increase as you moved toward
the center, creating what's called a "tidal force" on your
body.
 If you fell into a large enough black hole, no one
outside would be able to see you, but you'd have a view
of them. Meanwhile, the gravitational pull would bend
the light weirdly and distort your last moments of vision.

24.
What happens should you be sucked into a black
hole?
• Spaghettification is a theory as to what happens when
a person is sucked in. What happens is the gravity of
the black hole stretches your molecules so far you
become as thin as a piece of spaghetti, before
completely disintegrating.
• The other theory is you are simply pulled apart from a
tidal force that you snap apart at your weakest point
before being dismantled molecule by molecule.

25.
What happens to a spaceship that falls into a black
hole?
• We can escape from the surface of Earth in a
spaceship if the spaceship is accelerated fast enough
(about 11 km/sec) similarly you would need a force that
could accelerate your spaceship to faster than the
speed light travels to escape from a black hole - and
nothing we know of can exceed the speed of light.

26.
The whole process, from
the time you shut off
your engines, takes just
a few minutes.
Falling into a Black Hole.

27.
How have we existed so long if black holes are so
dangerous?
• The answer is :
1. Great distances between the stars .
2. All the stars are orbiting the center of the Galaxy.

28.
What are scientists trying to learn?
X-ray: NASA/CXC/U. Wisconsin/A.Barger
et al.; Illustrations: NASA/CXC/M.Weiss
NASA missions continue to search for and study black holes to
determine the fate of matter as it falls into black holes, how Schaller (for STScI)
Credit: NASA, ESA, and A.
powerful jets form, and what role black holes played in the
formation of the early universe.

29.
Conclusion
• When we look into the Universe today, we see that pretty much every
large galaxy has a super massive black hole in its heart. Even the Milky
Way has a black hole at its core with a mass of four millions times that
of the Sun.
– Black Holes are a long way off at least 26,000 light years (260
quadrillion kilometers)
– Its mass is still very small compared to the 200 billion solar masses
of our galaxy so it can’t really harm us.
– Even though black holes can cause death and destruction on a
major scale, they also help galaxies themselves form! So we owe
our existence to them. A
• Black holes may be used as worm hole in future in time travel.

30.
Thanks for
listening

31.
Any
queries?????