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BLACK HOLES

Presented To:MISS ANEELA HABIB

Presented By:WALEED EJAZ

Roll # 53, 3rd semester B.Sc (Hons) Applied Geology

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WHAT IS A BLACK HOLE?

A black hole is an object that is socompact that its gravitational force isstrong enough to prevent light or anything else from escaping.The term derives from the fact thatabsorption of visible light renders thehole's interior invisible, andindistinguishable from the black spacearound it.

Photo approved by NASAArtist concept of a black hole

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F ORMATION O F A BLACK HOLE

The most widespread support isgiven to the theory that a black holeis the natural end product of a giantstar's death.

A black holes is formed when a giantstar, at least three times bigger thanour own Sun, dies.Stars die when they run out of hydrogen or other fuel to burn.The formation of a black holeinvolves the phenomena of hydrostatic equilibrium

A black hole has the same mass asthe star from which it is formed.

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HI STORY OF BLACK H OLES

In 1783 , an English geologist named J ohnMichell first propsed the idea of blackholes.In 1795 , Pierre-Simon Laplace , a Frenchphysicist independently came to the sameconclusion.In 1916 , Albert Einstein wrote anexplanation of gravity called ³ The theory of general relativity ´ .

A few months later, K arl Schwarzschildgave the solution for the gravitational fieldof a point mass and a spherical mass.

Pierre-Simon Laplace

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HISTORY (cont.)

In 1939 , R obert Oppenheimer and H.Snyder calculated that a star would have tobe at least three times as massive as thesun to form a black hole.In 1970 , Stephen Hawking and R oger Penrose mathematically proved that blackholes are created naturally in the universe.The term " b lack hole " was introduced byJ ohn Archibald Wheeler in 1967 .

J ohn Archibald Wheeler

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BAS IC PARTS OF A BLACK H OLE

1. Singularity: All matter in a black hole is squeezed into a region

of infinitely small volume, called the central singularity.

2. Event horizon: The event horizon of a black hole is a surface

in a black hole that marks a point of no return.

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TYPES OF BLACK HOLES ON THE BASIS OF ROTATION

1 . Schwarzschild or Non-rotating black holes2 . K err or Rotating black holes

Parts of Schwarzschild or Non-rotatingblack hole:a) Singularityb) Event horizon

Parts of K err or R otating black hole:

a) Singularityb) Event horizonc) Ergosphered) Static limit

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TYPES OF BLACK HOLES ON THE BASIS OF SIZE

Type Mass Size

Supermassive black hole ~10 5 - 10 9 MSun ~0.001±10 AU

Intermediate-mass black hole ~10 3 M Sun ~10 3 km = R

Earth

Stellar-mass black holes ~10 M Sun ~30 km

Micro black hole up to ~ M Moon up to ~0.1 mm

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HOW WE CAN DETECT BLACK HOLES?

W e cannot see black holes directly, but their influence on the matter around them revealstheir presence.

Methods for detection:

1) To look for objects in our universe that havea lot of mass, but are very small.

2) To look for an acceleration of matter.3) Gravitational Lensing

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G RAVITATIONAL LENSIN G

A gravitational lens isformed when the light froma very distant, bright source

(such as a quasar) is "bent"around a massive object(such as a black hole)between the source objectand the observer. The

process is known asgravitational lensing. Simulation of Gravitational lensingby a black hole

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Black H oles from The Noble Qur¶an

The Qur¶an is aware of the phenomenon of "blackholes ´ .I swear b y the sky and (the phenomena of) Tariq.

And what will explain to you what Tariq is?I t is a star that pierces (or makes a hole).(Qur¶an 86:1-3)The Quran uses the word ³ Thaqi b´ in Arabic, a wordthat literally signifies a puncture or a minute hole

Martin Rees, states in ³O ur Cosmic Ha b itat ́ (2001)"Space is already being punctured by the formationof black holes..."(Rees, page 120)

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W EB REFERENCES

1. www.wikipedia.org/wiki/Black_hole2. www.imagine.gsfc.nasa.gov/docs/science/black_holes.html3. www.hubblesite.org/explore_astronomy/black_holes4. www.geocities.com/blackholeinfo5. www.amazing-space.stsci.edu/capture/blackholes