21^st Century Astronomy, Second Edition

Chapter 16: Stars in the Slow Lane

Study Plan

Within its core the Sun fuses over 4 billion kilograms of hydrogen to helium each second; and although the Sun may seem immortal by human standards, eventually it will run out of fuel. When it does, some 5 billion years from now, the Sun's time on the main sequence will come to an end. As we examine what happens when a low-mass star like the Sun nears the end of its life, we will find that

• The more massive a star, the shorter its lifetime.
• We can follow the post-main sequence evolution of stars by tracing their paths on the H-R diagram.
• When the Sun runs out of fuel at its center, it will grow into a larger, more luminous red giant star.
• Red giants, and some other evolved stars, are shaped by dense "degenerate" cores in which atoms have been crushed by gravity.
• Evolving low-mass stars go through a series of stages, eventually burning helium to carbon and building up a core of carbon ash.
• In the end a low-mass star will eject its outer layers, possibly forming a planetary nebula, and leaving behind a tiny degenerate white dwarf.
• Low-mass stars in binary systems may experience more exciting fates as novae or supernovae.

Organize

1. Read Chapter 16 in your textbook or ebook.
2. Take the Diagnostic Quiz to assess your understanding of the basic concepts and identify gaps in your understanding of the assigned reading.

Learn

1. Use the FlashCards to test your memory for new terms.
2. If your instructor has assigned SmartWork online homework, login from the right navigation pane for additional practice and review.

Connect

1. Periodic Connections boxes and the Seeing the Forest through the Trees section at the chapter's end draw your attention to recurring themes and help prepare you for concepts explored more fully in subsequent chapters.
2. Visit Astronomy in the News for breaking news of new discoveries and the opportunity to apply what you've learned in this chapter to real-world (and real Universe) events.

Instructors now have an easy way to collect students’ online quizzes with the Norton Gradebook without flooding their inboxes with e-mails.

Students can track their online quiz scores by setting up their own Student Gradebook.