Sections Review

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Vocabulary

Formulae

1. Escape velocity = Sqrt[2G × Mass)/(distance to the center)], where G is the gravitational constant.
2. Event horizon (Schwarzschild radius) = 2G × (black hole mass)/c², where G is the gravitational constant, and c is the speed of light.
3. Event horizon = [3 × black hole mass] kilometers, where the black hole mass is measured in solar masses.
4. Maximum size of an object = fluctuation time interval × speed of light.

Review Questions

1. What type of star will become a white dwarf? Describe the characteristics of a white dwarf.
2. How does electron degeneracy pressure keep the white dwarf from collapsing any further?
3. What is the upper bound for the mass of a white dwarf? How would the fact that stars up to 5 solar masses become white dwarfs show that stars lose mass to the interstellar medium as they evolve? How is most of this mass lost?
4. How is a neutron star created? What type of star will become a neutron star? Describe the characteristics of a neutron star.
5. How does neutron degeneracy pressure keep the neutron star from collapsing to a point at the center?
6. What is the upper bound for the mass of a neutron star?
7. What are the ingredients for a pulsar?
8. Why does a pulsar spin so fast?
9. Why could a collapsed star spinning many times each second not be a regular star or white dwarf?
10. What type of star will become a black hole? Does anything keep it from collapsing to a point at the center? Describe the characteristics of a black hole.
11. What is the sole determining thing that specifies the size of the event horizon?
12. What are the signatures of a black hole---observations indicating the presence of a super-compact nearly invisible object?
13. How do the rapid fluctuations of the X-rays from a black hole's accretion disk show that the object at the center is small? If the fluctuations were slower (taking longer to brighten and then fade), would the implied size be smaller or larger?

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last updated: 25 May 2001