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Marion Mikusch
Physics institute, university of Graz
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molecules: do not have enough Ekin
triggers: compressions
Jeans mass and Jeans radius:
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contraction Epot is released
if heat is transported off collapse
free falling time:  protostar is born
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Different phases:
◦ hydrogen burning
◦ helium burning
◦ carbon, neon, oxygen, silicate burning
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stage of equilibrium until fuel is depleted
 a new thermonuclear process starts
Stars over 8 sm: also heavy elements are built
iron-nickel core is formed  supernova
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neutron star: e+pn
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until internal pressure prevents contraction
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Star over 30 sm: unstoppable collapse
 a black hole is born
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escape velocity reaches the
speed of light
Schwarzschild radius:
 causal border
black hole with 10 sm:
Rs = 29,5 km
event horizon: surface around
the black hole
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interstellar matter approches
in spiral tracks
X-ray emission
rotation  space-time
geometry is distorted
‘electromagnetic tornado‘
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analogy between event horizon and entropy
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entropy: disorder of missing information in a system
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bit of information  area of the event horizon
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definition of entropy
and temperature
is possible
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paradox: finite temperature  emission of thermal
radiation??
Quantum mechanics: uncertainty principle
 virtual particles can arise in pairs
they disengage for a short time and than annihilate
mass of the black
hole decreases
 total evaporation
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Only 3 observable characteristics:
◦ mass
◦ angular momentum
◦ electric charge
huge information loss
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but a swallowed bit is ‘saved‘ in an area of the
event horizon  like a hologram
3-dimensional object memorized by a 2dimensional region
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