This is a brief explanation on black holes are formed and science behind it

1. Black
holes
By
JAHNAVI

2. A Brief History Of Black
Holes.
First proposed by John Mitchell in
1783
Later in 1916 Karl Schwarzschild
solves Einstein’s field equation for
space time
In 1887, MichelSon and Morley ‘s
experiment said that light travels at a
speed of 186,282 miles per second.

3. General Relativity
Published in 1915
Describes the
relationship between
mass and space_time.
Space_time was not flat
but it is wrapped and
curved by matter and
energy in it.
Confirmed in 1919 by
Arthur Eddington.

4. Spacetime:
• Apparent vs. real trajectory of a light beam

5. EVENt HorIzoN
A boundary in space time through which only
matter and light only can pass through inwards.
Not even light can escape from inside a event
horizon.
To a distant observer, clocks near a black hole
appear to tick more slowly than those further
away from the black hole.
Due to gravitational time dilation, an object
falling into a black hole appears to slow as it
approaches the event horizon.
any light emitted by the object to appear redder
and dimmer, an effect known as gravitational
redshift.[55] Eventually, the falling object
becomes so dim that it can no longer be seen.

6. Formation
Gravitational collapse
The gravitational collapse of heavy stars is
assumed to be one of the reasons for the
formation of stellar mass black holes.
Occurs when an object's internal pressure
is insufficient to resist the object's own
gravity.
For stars this usually occurs either
because a star has too little "fuel" left to
maintain its temperature .

7. • Black holes could also be formed in high-energy
collisions that achieve sufficient density .micro
black holes can be created in the high-energy
collisions that occur when cosmic rays hit the
Earth's atmosphere
• They could also possibly be created in the Large
Hadron Collider at CERN. These theories are very
speculative, and the creation of black holes in
these processes is deemed unlikely by many
specialists.Even if micro black holes could be
formed, it is expected that they would evaporate in
about 10−25 seconds, posing no threat to the
Earth.

8. On the basis of mass :three
classifications on blackholes
• Stellar mass: 3 to 20 times the
mass of the sun.
• Super massive: Black holes with
millions to billions of the mass of
our sun.
• Mid-Mass:In between stellar-
mass and super massive.

9. Growth
• 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 surroundings and
omnipresent cosmic background radiation.
• This is the primary process through which
supermassive black holes seem to have grown.
• A similar process has been suggested for the
formation of intermediate-mass black holes found
in globular clusters. Another possibility for black
hole growth, is for a black hole to merge with other
objects such as stars or even other black holes.

10. singularity
• Gravitational blackhole is present in the
centre of a blackhole, which is one
dimensional and laws of physics cease to
operate.
• A black hole’s singularity remains hidden
behind its event horizon.

11. In 1939 , Oppenheimer
shows massive stars
collapse to a singular
point.
Singularity surrounded
by event horizon, point
of no return.
A black hole can
essentially be described
by just three quantities:
how much mass is
entering into it,how fast
it is spinning and its
electrical charge.

12. ClassiC blaCk holes
In 1960s, Roger Penrose
prooved a theorem which
showed that the gravitational
collapse of a large dying
star might result in a
singularity.
• The simplest type of blackhole in which
the core doesn’t rotate and just has a
singularity and an event horizon is known
as schwarzchild blackhole
• Another type of blackholes are the
spinning ones discovered by Kerr.

13. 2 main types
Schwarzschild
• Static, no rotation
• Point-like singularity
• Event Horizon
Kerr
• Rotates
• Ring shaped singularity
• Inner Horizon
• Outer Horizon
• Ergosphere

14. 2 main types
Schwarzschild Kerr

15. Can BlaCk Holes
Radiate?
Maybe so…
• 1970 : Jacob Berkenstein suggests area of event
horizon is a measurement of black holes
entropy.
• 1970 : Stephen Hawking shows that area of
event horizon always increases.
• 1971 : Borisovitch Zel’dovitch claims rotating
black holes radiate until they stop spinning .

16. Hawking radiation:
• In 1974, Hawking predicted that
black holes are not entirely black
but emit small amounts of thermal
radiation which is known as
Hawking radiation.
• By applying quantum field
theory to a static black hole
background, he determined
that a black hole should emit
particles that display a perfect
black body spectrum. Since Hawking's
publication, many others have verified the result through various
approaches.

17. If Hawking's theory of black hole
radiation is correct, then black holes are
expected to shrink and evaporate over time
as they lose mass by the emission of
photons and other particles.
The temperature of this thermal
spectrum (Hawking temperature) is
proportional to the surface gravity of the
black hole, which, for a Schwarzschild
black hole, is inversely proportional to the
mass. Hence, large black holes emit less
radiation than small black holes.
If a black hole is very small, the radiation
effects are expected to become very
strong. Even a black hole that is heavy
compared to a human would evaporate in
an instant.

18. So What’S Left?
•Resolution of the “Information paradox”
•Development of an adequate quantum
theory of gravity, Relativity is no longer a
valid approximation on scales smaller
than the Planck length, lp = (hG/2πc3
)1/2
.

19. So Why Study BLack
hoLeS?
• Black holes push the limits of physical theories
• Among the most extreme phenomena in the
universe
• I think they’re cool.
• That’s it
• Thanks for listening
• The End
• (applause…. please?)

20. RefeRenceS :
• Kip Thorne, Black Holes And Timewarps (Norton, 1994)
• Eric Poisson, A Relativist's Toolkit, The mathematics of black hole mechanics
(Cambridge University Press, 2004).
• Alessandro Fabbri and Jos'{e} Navarro-Salas,Modeling Black Hole Evaporation
(Imperial College Press, 2005)
• John A. Wheeler, E.F. Taylor, Exploring Black Holes, Introduction to General
Relativity (Addison Wesley, 2000)
• Stephen Hawking, The Universe In A Nutshell (Bantam, 2001)
ImageS :
• http://chandra.harvard.edu/resources
• http://www.belmontnc.4dw.net/DWFNEU5.gif
• www.tqnyc.org/NYC040808/ neutron_star.jpg
• http://en.wikipedia.org
• www.scienceweek.at