(Background) Black holes can neither be seen nor drawn easily. In this artist's conception of the vicinity of a black hole, the disk-shaped region is a rapidly whirling collection of hot gas and dust about to fall into the black hole. The hole itself is represented merely by a black dot at the center of the accretion disk.
(Inset A) An artist's view of a nearly flat, spinning torus of heated gas, called an accretion disk. For a typical stellar black hole, the disk has solar-system dimensions.
(Inset B) A closeup view of the core of the accretion disk, showing a truncated cusp of very hot gas about to make its way down into the central black hole.
(Inset C) The anatomy of a hypothetical black hole would show its accretion disk to the left and right, with the hole itself still only a black point at the very center. The white vertical spike is a geyser (or jet) of matter shot away from near the hole perpendicular to the innermost part of the disk.
(Inset D) A closeup view of the previous cutaway drawing of the accretion disk, the jet, and the black hole at its heart. At this scale, the stellar black hole itself (still shown as a black dot in the magnified inset) is about 30 kilometers across—and on this scale, astronomers are very uncertain of what black holes really look like.
Studying this chapter will enable you to:
Describe the properties of neutron stars and explain how these strange objects are formed.
Explain the nature and origin of pulsars and account for their characteristic radiation.
List and explain some of the observable properties of neutron-star binary systems.
Describe how black holes are formed and discuss their effects on matter and radiation in their vicinity.
Relate the phenomena that occur near black holes due to the warping of space around them.
Discuss the difficulties in observing black holes and explain some of the ways in which the presence of a black hole might be detected.
Our study of stellar evolution has led us to some very unusual and unexpected objects. Red giants, white dwarfs, and supernova explosions surely represent extreme states of matter completely unfamiliar to us here on Earth. Yet stellar evolution can have even more bizarre consequences. The strangest states of all result from the catastrophic implosion—explosion of stars much more massive than our Sun. The almost unimaginable violence of a supernova explosion may bring into being objects so extreme in their behavior that they require us to reconsider some of our most hallowed laws of physics. They open up a science fiction writer's dream of fantastic phenomena. They may even one day force scientists to construct a whole new theory of the universe.
