Ch16 - Assignment: Chapter 16 Class: Astronomy I Date:...

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Assignment: Chapter 16 Class: Astronomy I Date: October 29 th , 2007 Review Questions 1. The total amount of energy emitted by the Sun each second is called the Sun’s luminosity. It is about 3.9 x 10 26 watts, or 3.9 x 10 26 joules of energy per second. 2. The Kelvin-Helmholtz contraction was a process that seemed to explain solar energy in the mid-1800s. The idea was that the tremendous weight of the Sun’s outer layers should cause the Sun to contract gradually, compressing its interior gases. But this idea was ruled out because it if were to be true, the Sun would have had to be much larger in the relatively recent past. 3. The burning of fuels cannot be an explanation for the Sun’s energy because it could not continue for a long enough time to explain the age of the Earth. 4. The process of converting hydrogen into helium is called hydrogen fusion. This is fundamentally unlike the burning of a log in fireplace because ordinary burning involves chemical reactions that rearrange the outer electrons of atoms with no effect on the atoms’ nuclei. Hydrogen fusion deals with hydrogen nuclei fusing together to produce a nuclear reaction. 5. If the electric force between protons became stronger, the temperature required for thermonuclear fusion has to be greater in order to overcome the electric repulsion of protons. 6. The Sun’s outer regions do not have enough heat and pressure to carry on the thermonuclear fusion. 7. In step 1, two hydrogen nuclei collide to create a proton and neutron, a hydrogen isotope. One byproduct is neutrino and the other is positron. In step 2, the hydrogen isotope collides with another proton to create helium isotope along with a byproduct of gamma-ray photon. In step 3, two helium isotopes collide to create
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Ch16 - Assignment: Chapter 16 Class: Astronomy I Date:...

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