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Homework, November 16, 2006 AST110-6 Due Date: Tuesday, November 28, 2006 1. Chapter 12, Problem 23 to 28 [60pt]. Homes to Civilization? We do not yet know how many stars have Earth-like planets, nor do we know the likelihood that such planets might harbor advanced civilizations like our own. However, some stars can probably be ruled out as candidates for advanced civilizations. For example, given that it took a few billion years for humans to evolve on Earth, it seems unlikely that advanced life would have had time to evolve around a star that is only a few million years old. For each of the following stars, decide whether you think it is possible that it could harbor an advanced civilization. Explain your reasoning in one or two paragraphs. a. b. c. d. e. f. A 10 Msun hydrogen-burning star. A 10 Msun brown dwarf. A 1.5 Msun hydrogen-burning star. A 1.5 Msun red giant. A 1 Msun helium-burning star. A red supergiant. 2. Chapter 12, Review Question 6 [20 pt]. Briefly explain the changes that the Sun will go through after it exhausts its core hydrogen. Be sure to explain both the changes occurring in the Sun’s core and the changes visible from outside the Sun. What do we mean by the stages we call hydrogen shell burning, helium burning, and double-shell burning? 3. The following table lists the spectral type and luminosity of 10 stars (A to J) [20pt]. a. Place the stars in the attached H-R diagram template according to their spectral type and luminosity. Label the stars clearly, like the Star S (the Sun) shown in the figure. b. List the stars that are likely to be main-sequence stars, c. supergiant or giants, and d. white dwarfs. Problem 3 continues in page 2. Star A B C D E F G H I J S Spectral Type G2 F5 A1 A2 K2 A0 B1 B1 M1 M4 G2 Luminosity (Solar Units) 1.6 7.4 26.0 0.002 0.37 60.0 100,000 23,000 38,000 0.005 1.0