Download Shedding Light on Black Holes

Mario Livio
Space Telescope Science Institute
Shedding Light on Black Holes
“Black holes have no hair”
Astrophysical black holes are in some sense
extremely simple objects characterized just by:
Mass
Spin
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Mass Determinations
Stellar
Supermassive
About 20 masses known
About 80 masses known
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Spin Determinations
Stellar
Using x-ray observations to
determine radius at inner edge
of the accretion disk.
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Spin Determinations
Supermassive
Using lines emitted by
iron atoms.
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General Relativity At Work
The emission of gravitational waves.
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Ultimate Goal: Quantum Theory of Gravity
Most of the time, gravity and quantum mechanics
“live” in their separate worlds…
Hubble Ultra Deep Field
HST • ACS
But they inevitably meet in two places:
Early Universe
Black
Holes
Big
Bang
M87
HST • WFPC2
Inflation
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First Clues for Quantum Effects
Entropy: The measure of the amount of disorder.
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First Clues for Quantum Effects
Entropy: The measure of the amount of disorder.
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First Clues for Quantum Effects
Entropy: The measure of the amount of disorder.
Second Law of Thermodynamcs:
The entropy of any isolated system (including the
universe as a whole) can never decrease.
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Hawking Radiation
Bekenstein: Black Holes
must have an entropy
Otherwise…
we would violate the second law
of thermodynamics.
The Area Theorem: When black holes interact with their
environment (by accreting gas or colliding with other
black holes) their area always increases.
Entropy = 1/4 Area
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Hawking Radiation
If black holes have thermodynamic properties like entropy,
they should also have a temperature:
They should radiate!
Virtual Pairs in Quantum Vacuum
Event Horizon
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A Success of String Theory
Black hole entropy agrees with
Bekenstein-Hawking formula.
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Cheshire Cat