CH 12 - Chapter 12 Review Questions 1. (c) Dust in...

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Chapter 12 Review Questions 1. (c) Dust in interstellar space scatters more blue light passing through it than shorter wavelength colors. Therefore, stars and other objects seen through interstellar clouds appear redder than they would otherwise. 2. (c) The lowest mass that an object can have and still maintain the fusion of normal hydrogen into helium as occurs in the Sun (see An Astronomer’s Toolbox 10-1) is 0.08 M Sun or about 75 times the mass of Jupiter. 3. (d) The fusion of hydrogen in its core 4. Giant molecular clouds are interstellar clouds with diameters ranging from 50 to 300 ly and containing from 10 5 to 2 × 10 6 solar masses of mostly hydrogen. 5. The higher their temperature, the faster gas particles move. This motion creates pressure in the gas. The hotter the gas, the higher its pressure. If the temperature in a clump of interstellar gas is very high, the pressure in that region would also be correspondingly too high and thus prevent it from collapsing. 6. The surface of a main-sequence star is too cool for thermonuclear reactions to occur there. Surface temperatures range from a few thousand to a few tens of thousands of Kelvins. Thermonuclear fusion requires temperatures higher than 10 million Kelvins. 7. An evolutionary track is the path on the Hertzsprung Russell, or H-R, diagram made by the changes in the temperature and luminosity of a star throughout its lifetime. By knowing the evolutionary tracks of stars with different masses, astronomers are able to use the H-R diagram to determine the masses and ages of the stars plotted on it. 8. Review Chapter 11 and see the H-R diagram in Figure 12-12. 9. Astronomers believe that the planets and Sun formed together. The planets, and hence the Sun, are slightly less than 5 billion years old. Because the main-sequence lifetime of a one solar mass star is 10 billion years, we can conclude that the Sun has another 5 billion years on the main sequence. 10. In 5 billion years the Sun will run out of hydrogen fuel in its core. Fusion there will temporarily cease
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CH 12 - Chapter 12 Review Questions 1. (c) Dust in...

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