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Lecture 10: Black Holes

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Lecture 10: Black Holes

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    3. Dark stars Rev. John Michell (1783) If there really should exist in nature any bodies whose density is not less than that of the sun, and whose diameters are more than 500 times the diameter of the sun their light could not arrive at us. Pierre Simon Laplace (1796) There exist in the heavens therefore dark bodies, as large as and perhaps as numerous as the stars themselves.

    7. Calculation of escape velocity

    8. Calculation of Schwarzschild radius

    9. Schwarzschild radii for different objects

    10. Earth as a depression in the space-time fabric

    11. A black hole is an infinite abyss in space-time

    12. Structure of a black hole

    13. Recall singular behaviour of electrons electric field E = Q / (4pe0r2) It is infinite when r = 0. Quantum field theory comes to the rescue

    14. Photon orbits around a black hole

    15. Falling into a black hole: time dilation

    16. Spaghettification!

    17. Singularity theorem Every black hole must have a singularity inside itself

    18. Naked singularity A singularity that is not inside a black hole (not surrounded by an event horizon), and therefore can be seen by someone outside it

    19. Cosmic censorship hypothesis The laws of physics prevent naked singularities from forming when a star collapses

    20. No-hair theorem A black hole has almost no hair; its only hair are its mass angular momentum electric charge

    22. Types of black holes Schwarzschild (1916) mass Reissner-Nordstrm (1916, 1918) mass, electric charge Kerr (1963) mass, angular momentum Kerr-Newman (1965) mass, angular momentum, electric charge

    23. Space-time diagram

    24. Schwarzschild black hole

    25. Reissner-Nordstrm black hole

    26. Kerr black hole

    27. Wormhole

    28. Energy extraction from a Kerr black hole

    29. Virtual particles In quantum theory, there is an intrinsic uncertainty in energy and time: ?E ?t = h/4p This implies the existence of virtual particles even in a vacuum Virtual particles appear in pairs, consisting of a particle and its corres- ponding antiparticle

    30. Hawking radiation One partner of a virtual-particle pair could fall into a black hole, carrying negative energy with it Effectively, the black hole appears to be emitting particles and losing mass!

    31. But this effect is very tiny for normal black holes For a solar mass black hole Temperature = 10-7 K Lifetime = 1067 years (age of universe = 1010 years) Since T ? 1/M, this effect is more pronounced for small black holes Mini black holes created during the Big Bang?

    32. Binary black hole system

    33. Microlens event http://hubblesite.org/newscenter/archive/2000/03/http://hubblesite.org/newscenter/archive/2000/03/

    34. Black hole in globular cluster http://hubblesite.org/newscenter/archive/2002/18/http://hubblesite.org/newscenter/archive/2002/18/

    35. Disk in galaxy NGC 7052 http://hubblesite.org/newscenter/archive/1998/22/http://hubblesite.org/newscenter/archive/1998/22/

    36. NGC 4438 http://hubblesite.org/newscenter/archive/2000/21/http://hubblesite.org/newscenter/archive/2000/21/

    37. Galaxy NGC 6251 nucleus http://hubblesite.org/newscenter/archive/1997/28/http://hubblesite.org/newscenter/archive/1997/28/

    38. M87 http://hubblesite.org/newscenter/archive/1999/43/http://hubblesite.org/newscenter/archive/1999/43/

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