Chapter 13

Choose the best answer to each of the following. Explain your reasoning with one or more complete sentences. Which of these objects has the smallest radius? (a) a \(1.2 M_{\mathrm{Sun}}\) white dwarf (b) a \(0.6 M_{\text {Sun }}\) white dwarf (c) Jupiter

Choose the best answer to each of the following. Explain your reasoning with one or more complete sentences. Which of these objects has the largest radius? (a) a \(1.2 M_{\text {Sun }}\) white dwarf (b) a \(1.5 M_{\text {Sun }}\) neutron star (c) a \(3.0 M_{\text {Sun }}\) black hole

Choose the best answer to each of the following. Explain your reasoning with one or more complete sentences. Which of these things has the smallest radius? (a) a \(1.2 M_{\text {Sun }}\) white dwarf (b) the event horizon of a \(3.0 M_{\text {Sun }}\) black hole (c) the event horizon of a \(10 M_{\text {Sun }}\) black hole

Choose the best answer to each of the following. Explain your reasoning with one or more complete sentences. What would happen if the Sun suddenly became a black hole without changing its mass? (a) The black hole would quickly suck in Earth. (b) Earth would gradually spiral into the black hole. (c) Earth's orbit would not change.

Choose the best answer to each of the following. Explain your reasoning with one or more complete sentences. Which of these isolated neutron stars must have had a binary companion? (a) a pulsar inside a supernova remnant that pulses 30 times per second (b) an isolated pulsar that pulses 600 times per second (c) a neutron star that does not pulse at all

Choose the best answer to each of the following. Explain your reasoning with one or more complete sentences. What would happen to a neutron star with an accretion disk orbiting in a direction opposite to the neutron star's spin? (a) Its spin would speed up. (b) Its spin would slow down. (c) Its spin would stay the same.

Choose the best answer to each of the following. Explain your reasoning with one or more complete sentences. Which of these binary systems is most likely to contain a black hole? (a) an X-ray binary containing an O star and another object of equal mass (b) a binary with an X-ray burster (c) an X-ray binary containing a G star and another object of equal mass

Choose the best answer to each of the following. Explain your reasoning with one or more complete sentences. Which of these black holes exerts the weakest tidal forces on an object near its event horizon? (a) a \(10 M_{\text {Sun }}\) black hole (b) a \(100 M_{\text {sun }}\) black hole (c) a \(10^{6} M_{\text {Sun }}\) black hole

Choose the best answer to each of the following. Explain your reasoning with one or more complete sentences. Where do gamma-ray bursts tend to come from? (a) neutron stars in our galaxy (b) black holes in our galaxy (c) extremely distant galaxies

Unanswered Questions. You have seen in this chapter that current theoretical models make numerous predictions about the nature of black holes but leave many questions unanswered. Briefly describe one important but unanswered question related to black holes. If you think it will be possible to answer this question in the future, describe how we could find an answer, being as specific as possible about the evidence needed. If you think the question will never be answered, explain why you think it is impossible to answer.