1. Universe Tenth Edition
Roger Freedman • Robert Geller • William Kaufmann III
Universe Tenth Edition
Chapter 21: Black Holes

3. By reading this chapter, you will learn
21-1 The main ideas of Einstein’s special theory of relativity
21-2 How Einstein’s general theory of relativity describes the nature of gravitation
21-3 The evidence for black holes in binary star systems
21-4 How the sudden formation of black holes can explain the mysterious gamma-ray bursts
21-5 How astronomers have detected supermassive black holes at the centers of galaxies
21-6 The simple structure of a nonrotating black hole
21-7 How just three numbers completely describe the properties of a black hole
21-8 What it might be like to approach a black hole
21-9 How black holes evaporate over time

4. 21-1: The special theory of relativity changes our conceptions of space and time
The Speed of Light is the Same to All Observers

5. The Speed of Light is the Same to All Observers

6. The Speed of Light is the Same to All Observers

7. The Speed of Light is the Same to All Observers

10. 21-2: The general theory of relativity predicts black holes
The Equivalence Principle

11. The Equivalence Principle

12. The Gravitational Curvature of Spacetime

13. The Gravitational Curvature of Spacetime

14. The Gravitational Deflection of Light

15. The Gravitational Deflection of Light

16. The Precession of Mercury’s Orbit

17. The Precession of Mercury’s Orbit

18. The Gravitational Slowing of Time and the Gravitational Redshift

19. The Gravitational Slowing of Time and the Gravitational Redshift

20. The Gravitational Slowing of Time and the Gravitational Redshift

21. The Gravitational Slowing of Time and the Gravitational Redshift

22. The Formation of a Black Hole

23. The Formation of a Black Hole

32. Curved Spacetime around a Black Hole

33. Curved Spacetime around a Black Hole

34. 21-3: Certain binary star systems probably contain black holes
X-Rays Generated by Accretion of Matter Near a Black Hole

35. X-Rays Generated by Accretion of Matter Near a Black Hole

36. The Environment of an Accreting Black Hole

37. The Environment of an Accreting Black Hole

38. 21-4: The most intense radiation bursts in the universe may be caused by the formation of black holes
Gamma Ray Bursts

39. Gamma Ray Bursts

41. The Host Galaxy of a Gamma Ray Burst

42. The Collapsar Model of a Long-Duration Gamma Ray Burst

43. 21-5: Supermassive black holes exist in the centers of most galaxies
A Supermassive Black Hole

44. An Intermediate-mass Black Hole?

45. 21-6: A nonrotating black hole has only a “center” and a “surface”
The Structure of a Nonrotating (Schwarzschild Black Hole

46. Black Hole “Urban Legends”

47. Black Hole “Urban Legends”

48. 21-7: Just three numbers completely describe the structure of a black hole
The Structure of a Rotating (Kerr) Black Hole

49. A Rotating Supermassive Black Hole

50. The View Approaching a Black Hole

51. 21-8: Falling into a black hole is an infinite voyage
Effect of a Black Hole’s Tidal Force on Infalling Matter

52. 21-9: Hawking radiation and black hole evaporation
Hawking Radiation and Evaporation of a Black Hole

53. Hawking Radiation and Evaporation of a Black Hole

54. Key Ideas
The Special Theory of Relativity: This theory, published by Einstein in 1905, describes how measurements of lengths and durations of time depend on the motion of an observer and can appear different to different observers.
The speed of light is the same to all observers, no matter how fast they are moving.
An observer will note a slowing of clocks and a shortening of rulers that are moving with respect to the observer. This effect becomes significant only if the clock or ruler is moving at a substantial fraction of the speed of light.
Space and time are not wholly independent of each other, but are aspects of a single entity called spacetime.

55. Key Ideas
The General Theory of Relativity: Published by Einstein in 1915, this is a theory of gravity. Any massive object causes space to curve and time to slow down, and these effects manifest themselves as a gravitational force. These distortions of space and time are most noticeable in the vicinity of large masses or compact objects.
The general theory of relativity is our most accurate description of gravitation. It predicts a number of phenomena, including the bending of light by gravity and the gravitational redshift, whose existence has been confirmed by observation and experiment.

56. Key Ideas
The general theory of relativity also predicts the existence of gravitational waves, which are ripples in the overall geometry of space and time produced by moving masses. Gravitational waves have been detected indirectly, and specialized antennas are under construction to make direct measurement of the gravitational waves from cosmic cataclysms.
Black Holes: If a stellar corpse has a mass greater than about 2 to 3 M, gravitational compression will overwhelm any and all forms of internal pressure.
A black hole has an escape speed greater than the speed of light.
Nothing, not even light, can escape a black hole once it crosses into a black hole’s event horizon.

57. Key Ideas
Observing Black Holes: Black holes have been detected using indirect methods.
Some binary star systems contain a black hole. In such a system, gases captured from the companion star by the black hole emit detectable X rays. The emission comes from outside the event horizon.
Many galaxies have supermassive black holes at their centers. These are detected by observing the motions of material around the black hole.

58. Key Ideas
Gamma-Ray Bursts: Short, intense bursts of gamma rays are observed at random times coming from random parts of the sky.
By observing the afterglow of long-duration gamma-ray bursters, astronomers find that these objects have very large redshifts and appear to be located within distant galaxies. The bursts are correlated with supernovae, and may be due to an exotic type of supernova called a collapsar.
The origin of short-duration gamma-ray bursters is unknown.

59. Key Ideas
Properties of Black Holes: The entire mass of a black hole is concentrated in an infinitely dense singularity.
A black hole has only three physical properties: mass, electric charge, and angular momentum.
A rotating black hole (one with angular momentum) has an ergoregion around the outside of the event horizon. In the ergoregion, space and time themselves are dragged along with the rotation of the black hole.

60. Key Ideas
Black holes emit Hawking radiation from a quantum physics process that occurs just outside of their event horizons.
Black holes have temperatures and their Hawking radiation is emitted like the blackbody radiation that is emitted by any object with a temperature.
Black holes can evaporate, but in most cases at an extremely slow rate unless the black holes are very small