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Black Holes

Black Holes. Gregory R. Sivakoff University of Virginia. Black Holes. What is a Black Hole? How Do We Know Black Holes Exist? Why Do We Study Black Holes?. Understanding the GRAVITY of the Situation. The gravitational force between two objects depends on their Masses their Separation.

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Black Holes

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  1. Black Holes Gregory R. Sivakoff University of Virginia

  2. Black Holes • What is a Black Hole? • How Do We KnowBlack Holes Exist? • Why Do We StudyBlack Holes?

  3. Understanding the GRAVITY of the Situation The gravitational force between two objects depends on • their Masses • their Separation

  4. Understanding the GRAVITY of the Situation 2

  5. Gravity & Orbits

  6. crush Escape Velocity D =8000 miles M = 1025 kg Vesc = 25,000 miles/hour D = 800 miles M = 1025 kg Vesc = 79,000 miles/hour

  7. General Relativity:Mass Warps Spacetime • Space and time must be considered together • Gravity is really a warping of space and time • Denser objects warp spacetime more

  8. Warped Space-time

  9. Gravitational Lensing

  10. Gravitational Lensing

  11. Curving Light

  12. crush(not to scale) Escape Velocity D =8000 miles M = 1025 kg Vesc = 25,000 miles/hour D = Vesc = 2/3 inch M = 1025 kg Vesc = 186,000 miles/second

  13. The Event Horizon:Boundary of a Black Hole • Nothing inside the radius of the event horizon, not even light, can escape • Mass Radius  • 1.8 miles for Sun • To the Moon for 400,000 Suns

  14. Knowledge About What Is Inside The Event Horizon • Charge (most likely neutral) • Spin • Non-spinning (unlikely) • Spinning • Mass (In units of the Sun) • Stellar mass (~3-30) • Supermassive (~100,000-billions)

  15. Black Holes Are Dense • Minimum density of a Solar Mass Black Hole is similar to that of an Atomic Nucleus • But, we believe black holes have (nearly?) infinite density

  16. Formation ofStellar Mass Black Holes

  17. Formation ofSupermassive Black Holes • The first massive stars make large stellar mass black holes • Massive stellar mass black holes sink to center of a galaxy • Black holes mere and grow in dense stellar center

  18. How Do We KnowBlack Holes Exist?

  19. Cygnus X-1

  20. Cygnus X-1:X-ray Image

  21. Cygnus X-1:Optical Image Supergiant Star25 Solar Masses

  22. Cygnus X-1:Determining the Orbit Orbit Indicates 35 Solar Masses

  23. Cygnus X-1:The Whole System Black Hole 10 Solar Masses X-rays fromorbitting material Supergiant 25 Solar Masses Most of optical light

  24. Sagittarius (teapot) Galactic Center The Galactic Center 1 deg = 450 lyr Next Slide 5 arcsec = 0.6 lyr

  25. The Galactic Center 3.6 Million Solar Masses in 70 Earth Radii

  26. Why Do We StudyBlack Holes • Exceptionally energetic • Stellar Mass Black Holes areremnants of massive stars • Supermassive black holes may interact with galaxy and affect how galaxies evolve

  27. Comparison of Energetics

  28. Bright Shining Beacons

  29. Stellar Mass Black Holes:Massive Stellar Remnants

  30. We Are Made Of Star Dust

  31. Supermassive Black Holes Affect Galaxy Evolution

  32. What Is A Black Hole • Black Holes are extremely (infinitely?) dense concentrations of matter • They are so dense they create regions of space from which nothing can escape • The strong effects of gravity lead to interesting behavior, but they do not suck things in

  33. How Do We KnowBlack Holes Exist? • We can study the space outside a Black Hole • By measuring the mass and density of an object, we can prove it is most likely a Black Hole

  34. Why Do We StudyBlack Holes • Black Holes can lead to extremely energetic phenomena • Black Holes are the remnants of the massive stars whose dust we are made of • Supermassive Black Holes may affect how galaxies evolve

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