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Black Holes The Science Behind The Science Fiction

Black Holes The Science Behind The Science Fiction. Eliot Quataert (Berkeley Astronomy Dept). Science Fiction. “A Journey That Begins Where Everything Ends”. “Infinite Space, Infinite Terror”. A Muse for Popular Culture. The Far Side. The giant Schilling vortex has

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Black Holes The Science Behind The Science Fiction

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  1. Black HolesThe Science Behind The Science Fiction Eliot Quataert (Berkeley Astronomy Dept)

  2. Science Fiction “A Journey That Begins Where Everything Ends” “Infinite Space, Infinite Terror”

  3. A Muse for Popular Culture The Far Side The giant Schilling vortex has become the black hole of popular culture, sucking in all images and sound and allowing only soundbites about The Great Pitcher’s courage and legacy to escape. Angry Yankee’s Fan Gary Larson “Suddenly, through forces not yet fully understood, Darren Belsky’s apartment became the center of a new black hole”

  4. What is a black hole? • Do BHs exist in Nature? • YES! • How do we find them? • What do they look like?

  5. First, Something Simpler: Stars Pressure Balances Gravity From www.astronomynotes.com The Sun

  6. Eluding Gravity’s Grasp Escape Velocity Escape Velocity Speed Needed To Escape An Object’s Gravitational Pull Mass M Radius R Earth: Vesc = 27,000 miles/hour (11 km/s) Sun: Vesc = 1.4 million miles/hour (600 km/s)

  7. “Dark Stars”Rev. John Michell (1783) & Pierre-Simon Laplace (1796) Speed of light  1 billion miles/hour (3x105 km/s) • What if a star were so small, escape speed > speed of light? A star we couldn’t see! Earth mass: R  1 inch Solar mass: R  2 miles Vesc = speed of light 

  8. 1915: General Relativity, Einstein’s Theory of Gravity 1916: Schwarzschild’s Discovery of BHs in GRBHs only understood & accepted in the 1960s (Term “Black Hole” coined by John Wheeler in 1967) Albert Einstein Karl Schwarzschild

  9. Black Holes in GR If an object is small enough, gravity overwhelms pressure and the object collapses. Gravity is so strong that nothing, not even light, can escape. “Radius” of a BH  2 miles for a solar mass  1 inch for an Earth mass NOT a solid surface All Mass at the Center (GR not valid there)

  10. Dispelling the Myths … • BHs are not cosmic vacuum cleaners:only inside the horizon is matter pulled inexorably inward • Far away from a BH, gravity isno differentthan for any other object with the same mass • If a BH were to replace the sun, the orbits of planets, asteroids, moons, etc., would beunchanged (though it would get really really cold).

  11. How do we find BHs in Nature? Sidney Harris “It’s black, and it looks like a hole. I’d say it’s a black hole.”

  12. Where are BHs Found? Centers of Galaxies Binary Stars 1 BIG BH per galaxy million-billionx mass of sun formation not fully understood millions of ‘little’ BHs per galaxy ~ 10 x mass of sun formed by collapse of a massive star

  13. Shedding Light on BHs: X-ray Binaries Gas falling into a BH gets very hot and emits lots of radiation in X-rays Accretion is how we “see” a black hole Matsuda If two stars orbit close enough to each other, mass gets pulled from one and falls (accretes) onto the other. The smaller the target object, the faster the gas moves and the hotter it gets.

  14. How do we know it’s a BH? • Nature is tricky: couldn’t it be another “small star” like a neutron star or a white dwarf? • Measure mass of “X-ray star” by motion of its companion (a star like the sun)

  15. How do we know it’s a BH? • Nature is tricky: couldn’t it be another “small star” like a neutron star or a white dwarf? • Measure mass of “X-ray star” by motion of its companion (a star like the sun) Mass > 3 solar masses  BH! • Roughly a dozen BHs found this way (tip of the iceberg) Chandrasekhar

  16. Where are BHs Found? Centers of Galaxies Binary Stars 1 BIG BH per galaxy million-billionx mass of sun unclear how they form millions of ‘little’ BHs per galaxy ~ 10 x mass of sun formed by collapse of a massive star

  17. The Milky Way Galaxy: ~ 100,000 light-years across Scale: Size of Solar System: 0.01 light-years Typical Distance btw. Stars: 1 light-year 4 106 Msun Black Hole Central Black Hole Mass: 4 millionMsun Also ~ millions of 10 Msun BHs

  18. Stars in the Central Light-Year of the Galaxy Keep Zooming In …

  19. Evidence for a Big BH at the center of our Galaxy Motion of stars at the center of the Milky Way over the past decade Genzel et al; also Ghez et al. 10 light-days  size of solar system

  20. Evidence for a Big BH at the center of our Galaxy Velocities & Orbits of Stars  Mass BH in our Galaxy weighs in at 4 MILLION SOLAR MASSES Genzel et al; also Ghez et al. 10 light-days  size of solar system

  21. Light From Gas Falling Into the Black Hole BH Infrared Image X-ray Image Analogy: Solar Flare

  22. Many Varieties of Massive BHs Our Galaxy Brightness of Central Black Hole

  23. “Active Galactic Nuclei” radio image The BH ejects beams (“jets”) of matter & energy far outside its host galaxy into the surrounding universe The BH can outshine all of the stars in its host galaxy!

  24. The Moral of the Story … • Physicists said that Black Holes could exist • the ultimate victory of gravity over all other forces • Astronomers find that BHs do exist • 1 Big BH per galaxy (~ million-billion solar masses) • millions of little BHs per galaxy ( ~ solar mass) • BHs are responsible for the most dramatic and energetic phenomena in the universe • BHs are “seen” via the light produced by infalling gas & via the gravitational pull that they exert on nearby objects

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