Chapter 1. The Sun and the Nature of the Solar System
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~ ~ ~ CHAPTER 1 The Sun and the Nature of the Solar System 1. List characteristics of the solar system that are major clues in devising an hypothesis of its origin and evolution. 2. The theory of origin of the solar system most widely accepted by professional astronomers at present is principally due to (a) Velikovsky; (b) Menzel; (c) Oort; (d) Kuiper. 3. In the nebular theory of the origin of the solar system, it is visualized that all of the planets (a) were developed by accretion from a primordial cloud of gas and dust; (b) are fragments of the Sun that resulted from disruptive tidal forces of a passing star; (c) have the same average chemical composition; (d) are captured bodies that were moving previously through interstellar space. 4. The general theory of stellar evolution indicates that (a) the Sun will change to a pulsating star within about one million years from now; (b) the Sun will have about its present size and brightness for at least another billion years; (c) the Sun's brightness will decrease at the rate of about one percent per year during the next 100 years; (d) the Sun's brightness will increase by about one percent per year during the next 100 years. 1 2 / The Sun and the Nature of the Solar System 5. Current theoretical models of the interior of the Sun have all but one of the following features: (a) The temperature at the center is enormously greater than at the surface of the photosphere. (b) Elements such as iron, nickel, chromium, and molybdenum are concentrated near the surface. (c) Most of the atoms in the Sun are partially or completely ionized. (d) The density at the center is about 160 g cm-3 . 6. The Sun (a) is the largest object in the solar system; (b) is an excellent example of a pulsar; (c) is properly classified as a very large planet; (d) has an estimated lifetime of about three million years. 7. It is generally considered by astronomers (a) that few, if any, stars other than the Sun have planets; (b) that Kepler's laws are not applicable outside of the solar system; (c) that there probably are planetary systems associated with many millions of other stars. 8. The principal source of the energy emitted by the Sun is (a) decay of radioactive substances; (b) chemical combustion; (c) gravitational contraction; (d) nuclear fusion of hydrogen to form helium. 9. At 1 AU (150,000,000 km) sunlight provides a power flow of 1.4 kilowatts per square meter. Hence the total power flow from the Sun in all directions is kilowatts. 10. What is the basis for the claim that hydrogen is the principal constituent of the Sun? 11. Most of the light from the Sun comes from (a) the corona; (b) flares; (c) the photosphere; (d) the chromosphere. 12. The temperature of the Sun's photosphere is about (a) 1,000,000; (b) 15,000,000; (c) 20,000; (d) 5,800 degrees Kelvin. The Sun and the Nature of the Solar System / 3 13. The solar spectrum has its greatest intensity (a) at radio frequencies ; (b) in the infrared portion of the spectrum; (c) in the blue-green portion of the spectrum; (d) in the ultraviolet portion of the spectrum. 14. Fraunhofer lines are (a) thin, bright filaments seen in photographs of the Sun in the light of atomic hydrogen; (b) emission lines in the spectrum of the whole disc of the Sun; (c) emission lines in the coronal spectrum as observed during total eclipse of the Sun; (d) absorption lines of many different elements in the spectrum of the whole disc of the Sun. 15. The presence of specific chemical elements in the solar atmosphere is revealed by what features in the spectrum of the Sun? 16. The atomic composition of the outer layers of the Sun has been learned principally from study of (a) absorption lines in the spectrum of photospheric light; (b) the application of Wien's law to the solar spectrum; (c) the Doppler shift of the Ha emission line in solar flares; (d) the average density of the Sun, taken as a whole. 17. Under the assumptions that the Sun is spherically symmetrical and that its density declines linearly with radial distance from some specific value at the center to zero at the top of the photosphere , find the radius of the spherical shell that encloses 50 percent of the mass. Call the...