Black holes

IN THE NAME OF ALLAH , THE MOST GRACIOUS AND MERCIFUL

BLACK HOLES By Rizwan Akber 03F-EE-51 Sajjad Haider 03F-EE-76

Introduction Black holes: ,[object Object],[object Object],Foundation of the study= Albert EINSTEIN’s Theory of General Relativity four dimensionnal space: space-time

[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

What is a black hole ? 2. Definition 3. Structure of black holes 4. Properties and representations of black holes ,[object Object]

[object Object],[object Object],[object Object]

1915: General Relativity, Einstein’s Theory of Gravity 1916: Schwarz child's Discovery of BHs in GR BHs only understood & accepted in the 1960s (Term “Black Hole” coined by John Wheeler in 1967) Karl Schwarzschild Albert Einstein

2. Definition Black holes = very massive bodies speed of release at the surface > speed of light light can’t escape from a black hole Black holes are hidden

3. Structure A black hole is divided into 2 main parts : The SINGULARITY = a little ball At the center of the black hole ,[object Object],[object Object],[object Object],The IMMATERIAL SPHERE Around the singularity = a zone of no return ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

4.Properties and representations ,[object Object],[object Object],[object Object],[object Object],[object Object]

Black Holes: Do They Really Exist? We cannot see black holes directly, so we have to look for indirect evidences… What would you look for to find a stellar-massed black hole, like those formed after the death of high mass stars? To look for black holes formed by the death of high mass stars, we can look for binary systems that allows us to determine the mass of the objects. If we find an object with mass exceeding 3 M ⊙ , but is neither a regular star, nor a neutron star, then we can argue that it may well be a black hole .

Cygnus X-1 An x-ray source What do we see? A star (HDE 226868) - not a source for x-rays Where do the x-rays come from? HDE 226868 is in a binary system - orbiting something that is massive, but unseen!

Black hole classifications ,[object Object],[object Object],[object Object],[object Object]

1. Stellar black holes ,[object Object],[object Object],[object Object]

2. Supermassive black holes ,[object Object],Our galaxy : the MILKY WAY Sagittarius constellation

Supermassive black holes ,[object Object]

Supermassive black holes Credit: C.M. Urry & P. Padovani

Observations of supermassive black holes ,[object Object],[object Object]

3. Primordial black holes ,[object Object],[object Object],high temperature high pressure

How We Detect Black Holes ,[object Object],[object Object],[object Object],[object Object]

X-rays ,[object Object],[object Object],[object Object],[object Object]

Rotating stars ,[object Object]

Gravity lenses ,[object Object]

Observations of black holes ,[object Object],[object Object],[object Object]

Where are BHs Found? Centers of Galaxies Binary Stars 1 BIG BH per galaxy million-billion x mass of sun formation not fully understood millions of ‘little’ BHs per galaxy ~ 10 x mass of sun formed by collapse of a massive star

Conclusion ,[object Object],[object Object],[object Object],[object Object],[object Object],Astrophysicists can only watch indirect proofs about their presence in the universe up to now . BHs are responsible for the most dramatic and energetic phenomena in the universe BHs are “seen” via the light produced by infalling gas & via the gravitational pull that they exert on nearby objects

Black holes

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