session: 2011-12 black hole submitted by: submitted to: dr.a.k.srivastava under supervision of: shri...
TRANSCRIPT
KAMALA NEHRU INSTITUTE OF PHYSICAL
& SOCIAL SCIENCE
SESSION: 2011-12
Black hole
SUBMITTED BY: SUBMITTED TO:
Dr.A.K.SRIVASTAVA
UNDER SUPERVISION OF:SHRI SUSHEEL SINGH
M.Sc FINAL
Amaresh Singh
Some Definitions of BLACK HOLES
black hole is just another thing a star can turns in to when it runs out of fuel.or it is x star
Black holes are the cold remnants of former star ,so dense that no matter not even light is able to escape their powerful gravitational pull.
KINDS OF BLACK HOLES
Stellar black holes. Super massive black hole An Intermediate mass black hole Mini black hole Worm holes
Stellar Mass – must be at least 3 solar masses (~1034 g)Intermediate Mass – a few thousand to a few tens of thousands of solar masses; possibly the agglomeration of stellar mass holesSuper massive – millions to billions of solar masses; located in the centers of galaxies
Some technical terms
Schwarz schild radius. SingularityEvent horizon, Escape velocity.
Schwarzschild Radius and Event Horizon
Escape Velocity
Imagine feebly tossing a rocketship up in the air. It falls back to Earth because its kinetic energy was less than its gravitational potential energy.
However, toss it with a larger and larger velocity and it will go higher and higher before falling back to Earth.
There is a velocity above which it will not return to Earth -- this is the escape velocity.
Escape Velocity
To determine the escape velocity from Earth you set the gravitational potential energy equal to kinetic energy and solve for velocity
Vescape 2 GM
R
Radius from which you want to escape
Mass of theobject from which you want to escape
Note that the escape velocity doesn’t depend on the mass of the escaping body.For the Earth, put in the mass and radius of the Earth (for escape from the surface of the Earth) and you get: Vesc= 11 km/sec = 25,000 miles/hr
Now suppose you shrink the Earth to 1/100 of its current radius (at constant mass). What
happens to Vesc?
As R goes up, Vesc goes down
As R goes down, Vesc goes up
Don’t forget the square root
For this case, Vesc increases by 10x
Vesc 2GM
R
Vesc 1
R
Reduce the radius of the Earth to 1cm and Vesc=c (speed of light)
In this new theory of Gravity, where photons are affected by gravity, if the escape velocity equals or exceeds the speed of light, that object can no longer be observed. This is a Black Hole
Properties & Structures
Three parameters completely describe the structure of a black
hole
MassAs measured by the black hole’s effect on orbiting bodies, such as another starTotal electric chargeAs measured by the strength of the electric forceSpin = angular momentumHow fast the black hole is spinning
Formation of black hole $ growth of black hole
Detection of BLACK HOLE
What would be happens when we get close to a black hole?
Time would slow (as seen by outside observers.) Falling person notices nothing, even crossing event horizon.
Light from falling person (to outside observers) becomes more and more redshifted. The person falling slowly disappears from view (to outside observers.
Gravitational “tidal forces” would stretch matter out into longer and longer, thinner and thinner strands.
Eventually all things that characterize matter would be gone. atoms molecules, protons, neutrons, electrons…
Everything is compressed into an infinitely small point of infinite density (the singularity).
All that remains is mass (energy) and angular momentum…
An astronaut descending down towards the event horizon of the
black hole will be stretched vertically (tidal effects) and
squeezed laterally unless the black hole is very large like thousands
of solar masses, so the multi-million solar mass black hole in the center of the galaxy is safe.
The only known places in the Universe where there could be enough mass in one area is in the center of massive galaxiesNot believed to be anywhere else
Where Could Super-Massive Black Holes Exist?
Which is The biggest black hole?
WHAT HAPPENS IF A BLACK HOLE HIT THE EARTH
EVIDENCE OF BLACK HOLE
MYTHS & FACTS OF BLACK HOLES
Black holes are completely black.
Matter which falls into a black holes reappears somewhere else in universe.
Every star that dies becomes a black holes
Black holes are massive vacuum cleaner , eating.
A black hole in space would devour everything in our galaxy.
Black holes is very dense.
AcknowledgementI am grateful to all respected teachers & specially shri Susheel singh & Satyendra pandey sir for his pleasant cooperation in collection & collation of information & material required for the preparation of this innovative representation.Last but not least I would like to thanks my parents & my friends specially those who work together as in terns at KNIPSS for the wise ideas throughout the project.
thanks