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Black Holes

Black Holes. • Regions of space from which nothing, not even light, can escape because gravity is so strong. • First postulated in 1783 by John Michell • Term “black hole” coined in 1969 • Observational evidence starting in 1970s. We see the effects a black hole has on matter and radiation

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Black Holes

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  1. Black Holes • Regions of space from which nothing, not even light, can escape because gravity is so strong. • First postulated in 1783 by John Michell • Term “black hole” coined in 1969 • Observational evidence starting in 1970s We see the effects a black hole has on matter and radiation near it; we have not yet seen a black hole directly.

  2. Journey to a Black Hole

  3. Schwarzschild BH Black Hole Structure • Schwarzschild radius defines the event horizon • Rsch = 2GM/c2 • Singularity is “clothed” inside the event horizon • Cosmic censorship prevails (you cannot see inside the event horizon)

  4. What is This? • Diagram of the effect of gravity (gravitational potential well) near the black hole on the fabric of spacetime • It is a 2-D depiction of a 3-D event

  5. Types of Black Holes • Primordial – can be any size, including very small (If <1014 g, they would still exist) • Stellar Mass – must be at least 3 solar masses(~1034 g) • Intermediate Mass – a few thousand to a few tens of thousands of solar masses; possibly the agglomeration of stellar mass holes • Supermassive – millions to billions of solar masses; located in the centers of galaxies

  6. The First “First” Black Hole • Cygnus X-1 binary system • Most likely mass is 16 (+/- 5) Mo • Mass determined by Doppler shift measurements of optical lines

  7. NGC 4261 • 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

  8. Supermassive Black Holes • Rotating black hole in the center of a galaxy, which is emitting relativistic jets of material • Emission is from just outside the event horizon

  9. Active Galaxies Jets of fast moving particles and gamma-rays Disk of galaxy with supermassive blackhole in center Halo of gas, and dust Quasars, Blazars, Seyferts, AGN, ….etc, etc, etc

  10. Radio & Optical Image of an AGN NGC 4261

  11. Chandra deep field Black Holes Are Everywhere! Black holes in empty space Deep Image Empty Black holes in“normal” galaxies Galaxy Black holes in quasars QSO

  12. Galactic Black Hole • Zooms in to show the region surrounding the black hole in the center of a galaxy • Accretion disk of gas swirls around black hole

  13. Galactic Black Holes • NGC 3377 & NGC 4486b are 2.7 arc-sec images • NGC 3379 is 5.4 arc seconds • Note double nucleus in central 0.5 arc-sec of NGC 4486b

  14. Colliding BHs • Spiral waveform can be calculated reliably • Ringdown after merger tells you the mass • Larger computers needed to predict the actual collision waveforms

  15. Gamma-ray Bursts! • Most powerful explosions in the Universe today - and one of the greatest mysteries of modern astrophysics • “When you see a gamma-ray burst, a black hole is being born” – M. Livio

  16. Gamma-ray Astronomy (The Short, Short Story…)

  17. Sources of g-ray Emission • Black holes • Active Galaxies • Pulsars • Gamma-ray bursts • Diffuse emission • Supernovae • Unidentified

  18. GRBs: The Very Brief Version • • Humble Beginnings: A Bomb or Not a Bomb? • Vela Program • • A few hundred events, a few hundred theories • • Finally, science to the rescue • Compton Gamma Ray Observatory • BeppoSAX/ROTSE/HST/ (and a host of others)

  19. Vela Program

  20. CGRO

  21. Gamma-Ray Bursts

  22. Distribution of GRBs in the Sky

  23. What BeppoSAX Saw

  24. What HST Saw (Much Later)

  25. Breakthrough!

  26. Models for GRBs Hypernova Merging Neutron Stars

  27. Come On…Let’s Vogue

  28. What’s Next • New Missions = Better Data • Improved theory • Serendipity

  29. New Missions = Better Data HETE II (launched 7 October 2000) INTEGRAL (2001) Swift (2003) GLAST (2005) Swift

  30. Imagine…we have detected a GRB! Our gamma-ray detector measures 5.27 x 10 -6 ergs/cm2 Hey, Laura! What’s so impressive about that?!??!!!

  31. Wrapping Up the Universe • The light we measure decreases as a function of distance, • We can find a galaxy’s distance if we can measure its velocity from its redshift, • By measuring the distances of gamma-ray bursts from their redshifts, we can see how amazingly powerful these events are.

  32. Remember the Falloff of Light What was emitted What you detect = 2 4 p D

  33. Remember Hubble’s Law v = Ho * d Ho is called the Hubble constant. It is generally believed to be around 65 km/sec/Mpc.

  34. v l - lo Dl = = = z l c lo Remember the Doppler Shift

  35. And Now for a Real Spectrum... This is an optical spectrum of a GRB from Keck, the world’s largest optical telescope. The locations of several Doppler shifted spectral lines are shown.

  36. A Little Musical Interlude

  37. A BIG Hint: From Redshift to Power Step-by-step power calculation: 1. Measure the redshift of three spectral lines 2. Take the average redshift, z 3. From this, calculate the velocity v=z*c 4. Using the Hubble Constant, get the distance d=v/Ho 5. Convert distance in Mpc to distance in cm 6. Now, with the distance to the GRB, and the value measured at our detector, calculate power: P=4πd2*measured flux

  38. Needed Information 1 Mpc ~ 3 x 10 19 km L = 5.3 x 10-6 ergs/cm2

  39. GRBs are the most Powerful Explosions in the Universe!

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