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Astronomy 350 Cosmology Professor Lynn Cominsky Department of Physics and Astronomy Offices: Darwin 329A and NASA EPO (707) 664-2655 Best way to reach me: [email protected] February 25, 2003 Lynn Cominsky - Cosmology A350 1 Black Holes and Cosmology BH are a possible endpoint of stellar evolution (from very massive stars) BH warp space and time around them, thereby affecting the evolution of the galaxies Central BH in galaxies may be the seeds that formed the galaxies and may be the only things left in the galaxies at the end of time Central BH in galaxies are signposts that help us find the earliest galaxies February 25, 2003 Lynn Cominsky - Cosmology A350 2 White Dwarfs, Neutron Stars and Black Holes White dwarfs are the size of the Earth and about 1 Mo Neutron stars are 10 km in radius and about 1.4 Mo One teaspoon of NS material weighs 100 million tons! After supernova, if cores are larger than 3 Mo , a black hole will be formed February 25, 2003 Lynn Cominsky - Cosmology A350 3 Masses of Black Holes Primordial – can be any size, including very small (If <1014 g, they would still exist) “Stellar mass” black holes – must be at least 3 Mo (~1034 g) – many examples are known Intermediate black holes – range from 100 to 1000 Mo - located in normal galaxies – many seen Massive black holes – about 106 Mo – such as in the center of the Milky Way – many seen Supermassive black holes – about 109-10 Mo located in Active Galactic Nuclei, often accompanied by jets – many seen February 25, 2003 Lynn Cominsky - Cosmology A350 4 Black Hole Structure Schwarzschild radius defines the event horizon Rsch = 2GM/c2 Not even light can escape, once it has crossed the event horizon Cosmic censorship prevails (you cannot see inside the event horizon) February 25, 2003 Schwarzschild BH Lynn Cominsky - Cosmology A350 5 The First Black Hole Cygnus X-1 binary system Most likely mass is 16 (+/- 5) Mo Mass determined by Doppler shift measurements of optical lines February 25, 2003 Lynn Cominsky - Cosmology A350 6 Journey to a black hole This video is slightly out of date – new NASA missions are now being considered instead of ARISE February 25, 2003 Lynn Cominsky - Cosmology A350 7 Binary star systems Often stars are formed in binary systems Since they have unequal masses, the more massive star will evolve faster - and reach the end of its main sequence lifetime In some cases, the supernova of the primary star will not disrupt the binary system and a COMPACT BINARY is formed Mass transfer can then occur from the main sequence star onto the collapsed, compact companion star - which can be a WHITE DWARF, NEUTRON STAR or BLACK HOLE February 25, 2003 Lynn Cominsky - Cosmology A350 8 X-ray Binary movie February 25, 2003 Lynn Cominsky - Cosmology A350 9 Measuring Mass At least 6 stellar mass BH exist in our galaxy Easiest to measure Doppler shift accurately when X-rays are not heating the accretion disk X-ray “novae” February 25, 2003 Lynn Cominsky - Cosmology A350 10 Rossi X-ray Timing Explorer Launched in 1995 – still operational Large area X-ray detectors to study timing details of material falling into black holes or onto the surfaces of neutron stars February 25, 2003 Lynn Cominsky - Cosmology A350 11 “Old Faithful” Black Hole movie Binary black hole system known as “microquasar” Regular X-ray outbursts discovered with RXTE Outbursts are linked to appearance of IR jets February 25, 2003 Lynn Cominsky - Cosmology A350 12 Milky Way’s Black Hole Best evidence comes from infrared measurements of stellar motion in central Milky Way by Ghez et al. and Genzel et al. S2, the closest star to Sgr A* (the radio source at the exact center of the Milky Way) indicates a mass of 2.6 million +/- 0.2 Mo S2 is at a distance of 17 lighthours from Sgr A* - whose event horizon is 26 light seconds February 25, 2003 Lynn Cominsky - Cosmology A350 movie 13 NGC 4261 – best HST photo 100 million light years away 1.2 billion Mo black hole in a region the size of our Solar System Mass of disk is 100,000 Mo Disk is 800 light years across February 25, 2003 Lynn Cominsky - Cosmology A350 14 Chandra X-ray Observatory Launched on July 23, 1999, it is the “Hubble” of X-ray astronomy – best images ever! Named after Subrahmanyan Chandrasekhar - Nobel prize winner who worked out the upper mass limit for white dwarfs (among many other things) February 25, 2003 Lynn Cominsky - Cosmology A350 15 Chandra finds black holes are everywhere! Deep Image Empty Black holes in empty space Black holes in“normal” galaxies Galaxy Black holes in quasars Chandra deep field February 25, 2003 QSO Lynn Cominsky - Cosmology A350 16 Albert Einstein “I want to know God's thoughts...the rest are details.” “Imagination is more important than knowledge. Knowledge is limited. Imagination encircles the world.” “With fame I become more and more stupid, which of “God does not course is a very common play dice with phenomenon.” the Universe” February 25, 2003 Lynn Cominsky - Cosmology A350 17 Einstein and Relativity 1905 – Theory of Special Relativity Applies to objects at a constant velocity Time dilation and length contraction Space and time are intertwined Matter and energy are equivalent 1916 – Theory of General Relativity Applies to objects that are accelerated Describes the effects of gravity on spacetime February 25, 2003 Lynn Cominsky - Cosmology A350 18 Einstein’s equation Gab = 8 p G Tab c2 where Gab describes the geometry of spacetime and Tab describes the flow of energy and momentum through spacetime “Matter tells spacetime how to curve and spacetime tells matter how to move” -- J. A. Wheeler February 25, 2003 Lynn Cominsky - Cosmology A350 19 Solutions to GR equations Non-rotating, spherical black hole (Schwarzschild) Rotating, axisymmetric BH (Kerr) Wormholes February 25, 2003 Lynn Cominsky - Cosmology A350 20 Andrew Hamilton’s BH Simulator Black hole (Schwarzschild geometry) with a simplistic accretion disk, seen through a telescope. The disk, actually a ring, is at the innermost stable circular orbit, colored according to the redshift. Notice the multiple images of the accretion disk. February 25, 2003 Lynn Cominsky - Cosmology A350 21 Andrew Hamilton’s black hole simulator In orbit around a Schwarzschild black hole, shooting simple cubes at it. The probes appear correctly lensed, redshifted, and time-delayed. Some probes are still en route to the black hole, while others, the red ones, appear frozen at the horizon. February 25, 2003 Lynn Cominsky - Cosmology A350 22 Hamilton’s black hole trajectory Minimum stable orbit is at 3 Schwarzschild radii or 300 km for this 30 Mo black hole In order to orbit any closer, you must fire thrusters to maintain forward motion February 25, 2003 Lynn Cominsky - Cosmology A350 23 Hamilton’s orbiting a black hole Orbiting the black hole at close to the photon sphere. We are moving at almost the speed of light, so the relativistic beaming effects are quite strong. February 25, 2003 Lynn Cominsky - Cosmology A350 24 Spacetime activity Bedsheet, small balls and heavy weight Try rolling the balls across the sheet with and without the weight Can you make a small ball curve in an orbit around the weight? February 25, 2003 Lynn Cominsky - Cosmology A350 25 Bob Nemiroff’s black hole movies Approaching a black hole February 25, 2003 Circling the black hole Lynn Cominsky - Cosmology A350 26 Nemiroff’s black hole movies Approaching the photon sphere February 25, 2003 Circling the BH at the photon sphere Lynn Cominsky - Cosmology A350 27 Hamilton’s Wormhole Complete Schwarzschild geometry consists of a black hole, a white hole, and two Universes connected at their horizons by a wormhole, also known as the Einstein-Rosen bridge February 25, 2003 Lynn Cominsky - Cosmology A350 28 Hamilton’s charged black hole passage Passing inward through the inner horizon of a charged black hole. The point at the center of the black disk is an image of our Universe, infinitely blueshifted, and should appear as an infinitely bright flash of light. The entire history of the Universe passes in that point. The region around the black disk also appears blue-shifted and brightened. February 25, 2003 Lynn Cominsky - Cosmology A350 29 Hamilton’s black hole into white hole Passing back through the inner horizon of a charged BH, into a white hole. The point at the center of the black disk is an infinitely blueshifted image of our Universe, that appears as an infinitely bright flash of light. The entire future of the Universe passes in that point. The point where we entered the inner horizon is at the bottom, and the point where we are exiting the horizon is at the center of the black disk. February 25, 2003 Lynn Cominsky - Cosmology A350 30 Hamilton’s white hole into new Universe Exiting the white hole into a new Universe, which appears as an infinitely blueshifted, infinitely bright, point at the center of the black disk. We see the entire history of the new Universe in the point. The noise texture continues to show how gas accreting on to the black hole in our original Universe would appear lensed and redshifted. February 25, 2003 Lynn Cominsky - Cosmology A350 31 Hamilton’s looking back on our Universe We are now in the new Universe, looking back at the white hole from which we have emerged. The new Universe is painted with the 2MASS Milky Way image. The view is redshifted and dimmed by our motion away from the white hole. Through the white hole we see light from our original Universe, multiply imaged. February 25, 2003 Lynn Cominsky - Cosmology A350 32 Hamilton’s escape from white hole universe If we accelerate back towards the white hole, in a frantic attempt to get back to our own Universe, we find that the white hole spontaneously turns into a black hole as we approach it. The accretion disk has been turned off for clarity. February 25, 2003 Lynn Cominsky - Cosmology A350 33 Gravitational Radiation General Relativity predicts the existence of gravitational radiation waves of gravity that travel at the speed of light The strongest signal comes from two black holes Black hole mergers in distant galaxies will test General Relativity in the extreme February 25, 2003 Lynn Cominsky - Cosmology A350 34 Laser Interferometric Gravitational Observatory LIGO Prototype Detector Engineering tests in 2003 February 25, 2003 Lynn Cominsky - Cosmology A350 35 Measuring Black Holes Mass and spin of black hole can be measured from the gravitational radiation patterns emitted in different situations Distorted Schwarzschild black hole February 25, 2003 Lynn Cominsky - Cosmology A350 Distorted Kerr black hole 36 Colliding Black Holes Spiral waveform can be calculated reliably Ringdown after merger tells you the mass Larger computers needed to predict the actual collision waveforms February 25, 2003 Lynn Cominsky - Cosmology A350 37 Colliding Black Holes movie Movie shows the event horizons merging as two black holes collide to form one larger black hole February 25, 2003 Lynn Cominsky - Cosmology A350 38 Colliding Black Holes Movie shows the movie blue and yellow gravitational waves emitted as the green event horizons of two black holes collide to form one larger black hole February 25, 2003 Lynn Cominsky - Cosmology A350 39 Laser Interferometer Space Antenna Launch 2010+ BH binaries BH collisions Galactic binaries February 25, 2003 Lynn Cominsky - Cosmology A350 40 Image a Black Hole! HST Image Close to the event horizon the peak energy is emitted in X-rays M87 0.1 arc sec resolution MAXIM 0.1 micro arc sec resolution 4-8 m arc sec Micro-Arcsecond X-ray Imaging Mission February 25, 2003 Lynn Cominsky - Cosmology A350 41 MAXIM Concept 32 optics (300 10 cm) held in phase with 600 m baseline to give 0.3 micro arc sec Optics 1 km 34 formation flying spacecraft 10 km Combiner spacecraft 500 km System is adjustable on orbit to achieve larger baselines February 25, 2003 Black hole image! Lynn Cominsky - Cosmology A350 Detector spacecraft 42 Stephen Hawking “God not only plays dice, he also sometimes throws the dice where they cannot be seen.” “My goal is simple. It is complete understanding of the universe, why it is as it is and why it exists at all.” “It is not clear that intelligence has any long-term survival value.” Proved that if GR is true and the universe is expanding, then a singularity existed at the birth of the universe February 25, 2003 Lynn Cominsky - Cosmology A350 43 Hawking Radiation Hawking radiation results from the formation of virtual particle pairs near the black hole’s event horizon. The total energy of the pair, E1 +E2 =0. According to quantum mechanics, virtual pairs of particles are always being created from the vacuum – they usually annihilate, disappearing back into the vacuum However, if the pair is formed near a black hole, one particle can become real (E1>0) and escape, while the other falls into the black hole The escaping particle makes Hawking radiation, while to conserve energy, the particle that falls in has to have E2<0, which lowers the energy of the black hole, and eventually causes it to evaporate. February 25, 2003 Lynn Cominsky - Cosmology A350 44 Hawking Radiation Hawking radiation from a very small black hole Hawking predicted that black holes should radiate due to the emission of charged particles Bigger black holes are colder and fainter Hawking radiation will eventually lead to the death of BH at the end of time February 25, 2003 Evaporation of miniblack hole in a gamma-ray burst Lynn Cominsky - Cosmology A350 45 Frame Dragging Predicted by Einstein’s theory of Precessing top General Relativity Rotating bodies drag space and time around themselves as they rotate – like a spinning object stuck in molasses It may have been observed by RXTE in neutron star and black hole binaries in oscillations caused by matter in precessing accretion disks February 25, 2003 Lynn Cominsky - Cosmology A350 46 Frame Dragging Gravity Probe B – to be launched in 2003 Will test 2 predictions of GR using 4 extremely accurate gyroscopes Measure space-time reference frame of Earth – gyroscopes will move 6.6 arcseconds per year Measure frame dragging of Earth – gyroscopes will move by 42 milliarcseconds per year These two effects are at right angles to each other February 25, 2003 Lynn Cominsky - Cosmology A350 47 Frame dragging activity Paper plate, honey, peppercorns, food dye, superball What happens when the ball spins? movie February 25, 2003 Lynn Cominsky - Cosmology A350 48 Web Resources Pictures from the Hubble Space Telescope http://oposite.stsci.edu/pubinfo/pictures.html Chris Hillman’s Relativity Page http://www.math.washington.edu/~hillman/relativity.html Andrew Hamilton’s Black Hole Flight Simulator http://casa.colorado.edu/~ajsh/bhfs/screenshots/ Stephen Hawking’s Home page http://www.hawking.org.uk/ Genzel Group Milky Way BH video http://www.eso.org/outreach/press-rel/pr-2002/pr-1702.html#vid-02-02 February 25, 2003 Lynn Cominsky - Cosmology A350 49 Web Resources Rossi X-ray Timing Explorer http://oposite.stsci.edu/pubinfo/pictures.html Gravity Probe B http://einstein.stanford.edu Micro-Arcsecond X-ray Imaging Mission http://maxim.gsfc.nasa.gov Laser Interferometric Space Array http://lisa.nasa.gov Bob Nemiroff’s black hole movies http://antwrp.gsfc.nasa.gov/htmltest/rjn_bht.html February 25, 2003 Lynn Cominsky - Cosmology A350 50