<p>Astronomy 1 ID: ______Name: ______</p><p>Astronomy 1 Homework #5</p><p>Answer following questions from the textbook. </p><p>Ch22</p><p>3. Astronomers find that 90% of the stars observed in the sky are on the main sequence of an H–R diagram; why does this make sense? Why are there far fewer stars in the giant and supergiant region?</p><p>9. Certain stars, like Betelgeuse, have a lower surface temperature than the Sun and yet are more luminous. How do these stars produce so much more energy than the Sun?</p><p>11. Why are star clusters so useful for astronomers who want to study the evolution of stars?</p><p>20. Where did the carbon atoms in the trunk of a tree on your college campus come from originally? Where did the neon in the fabled “neon lights of Broadway” come from originally?</p><p>Ch23</p><p>4. How do the two types of supernovae discussed in this chapter differ? What kind of star gives rise to each type?</p><p>6. If the formation of a neutron star leads to a supernova explosion, explain why only three of the hundreds of known pulsars are found in supernova remnants.</p><p>7. What is an event horizon? Does our Sun have an event horizon around it?</p><p>16. Arrange the following stars in order of their evolution: A. A star with no nuclear reactions going on in the core, which is made primarily of carbon and oxygen. B. A star of uniform composition from center to surface; it contains hydrogen but has no nuclear reactions going on in the core. C. A star that is fusing hydrogen to form helium in its core. D. A star that is fusing helium to carbon in the core and hydrogen to helium in a shell around the core. E. A star that has no nuclear reactions going on in the core but is fusing hydrogen to form helium in a shell around the core.</p><p>You do not have to write down the problems. This homework is due on 11/7.</p>