Black Holes in Universe - From Stellar Masses to Supramassive Objects in Galaxies
Max Camenzind
Center for Astronomy Heidelberg (ZAH)
@ Landessternwarte (2005)
Prologue: Chandrasekhar 1983
„The black holes of nature are the most perfect macroscopic objects there are in the universe: the only elements in their construction are our concepts of space and time. And since the general theory of relativity provides only a single unique family of solutions for their descriptions, they are the simplest objects as well.“
No matter is involved in their construction [i.e. no EOS], a Black Hole is a global vacuum solution with horizon, a kind of gravitational soliton.
Topics
The Long History of Black Hole Physics.
The Year 1963 and Kerr Black Hole Gravitational field is not Newtonian !
Evidence for the Existence of Black Holes 4 Classes of Astrophysical Objects. „No Hair Plane (Glatzenebene)“ (M,a).
Accretion: New Paradigm of disk accretion onto Black Holes (Balbus & Hawley 1991).
Magnetic Fields - The Spin Paradigm: The Ergosphere as a Source of Energy Launch Jets (Blandford & Znajek 1977) still largely not understood.
Beyond Einstein ? Dreams and Future
The Long Way towards BHs
1915: Einstein postulates the field equations (together with Hilbert).
1916: Schwarzschild Solution Schwarzschild radius RS = 2GM/c² = 3 km M / MS
Einstein denied the reality of Black Holes … He considered Black Holes as a mere mathematical curiosity.
This view changed after his death detection of Quasars (> 1963) observation of Cygnus X-1 (1971)
1963 – Foundation of Black Holes
1923 - Milestone 1: George Birkhoff: Schwarzschild spacetime geometry is the unique spherically symmetric solution of the Einstein vacuum field equations
1939 - Robert Oppenheimer & Hartland Snyder show gravitational collapse of a pressureless homogeneous fluid sphere formation of a trapped region
1963 – Milestone 2: Roy Kerr solves the Einstein vacuum field equations for uncharged symmetric rotating systems
1963 – Milestone 3: Quasars are detected fuelled by accretion onto Black Holes
1965 - Ezra Newman and collaborators solve the Einstein-Maxwell equations for charged rotating systems
1967 - Werner Israel presents proof of a "no hair" theorem
1968 – 1977: Golden Age
1968 – Brandon Carter uses Hamilton-Jacobi theory to derive 1st-order equations of motion for particle moving in Kerr black holes Kerr Ray-Tracing
1969 - Roger Penrose discusses the Penrose process for the extraction of the spin energy from a Kerr black hole Free energy of BHs
1971 – Milestone 4: Identification of Cygnus X-1/HDE 226868 as a binary black hole candidate system.
1973 - David Robinson completes the proof of the uniqueness theorem for Kerr black holes
1977 – Milestone 5: Blandford-Znajek Process electromagnetic spin energy extraction from rotating black holes
4 Laws of Black Hole Mechanics
1972 - Stephen Hawking proves that the area of a classical black hole's event horizon cannot decrease.
1972 - Jacob Bekenstein suggests that black holes have an entropy proportional to their surface area due to information loss effects
1973 - James Bardeen, Brandon Carter, and Stephen Hawking propose 4 laws of black hole mechanics in analogy with laws of thermodynamics Free energy
1973 - Stephen Hawking applies quantum field theory to black hole spacetimes and shows that black holes will radiate particles with a black-body spectrum which can cause black hole evaporation concept is important, but astrophysically not relevant, and still debated.
1978 – Sargent et al. show evidence for a supermassive BH in the center of Messier 87 (“serious possibility”). This has been very much debated but confirmed !
1992 – Microquasar GRS 1915+105 found.
1997 – Fe line redshifts of the innermost portions of accretion disks around rotating supermassive black holes
2000 - Evidence for the hypothesis that Sagittarius A* is a supermassive black hole at the centre of the Milky Way galaxy
2002 – The most distant Black Hole found: Cosmological Redshift z = 6.43 ! (< 1 Gyear old)
2005 – BHs confirmed in ~ 20 X-Ray Binary Systems !
Beyond Einstein: Is there really a Singularity in the Black Hole ?
Mottola-Mazur Gravastar 5 Layers
External Schwarzschild vacuum, r>2M
Thin shell at r > 2M, surface density + and surface tension.
[ Finite-thickness shell at r = 2M, stiff matter. ]
[ Second thin shell at r < 2M, surface density -, surface tension. ]
de Sitter vacuum inside: P = -c² bulk of mass no singularity r=0
Conclusions - Visions
Mass spectrum is continuous from stellar to 10 billion solar masses. Gap from 100 – 105 MS ?
But Kerr parameter a is not yet measurable !
GRMHD (> 2000) Plasma dynamics near BHs can be successfully treated within Godunov schemes Use Kerr coordinates, bc within horizon ! MRI accretion theory is now tractable !
Strong B-field limit (which is unphysical !): GR Magnetodynamics confirms BZ mechanism of energy extraction out of the ergosphere Jets are ergospheric plasma flows ?
Weak field limit of GRMHD (relevant for MRI) is in unsatisfactory state, most results based on non-conservative methods Turbulent accretion to rotating BHs essentially unsolved, but now tractable with modern methods.
