To all but the most powerful of telescopes, a star is just a point of light in the night sky. But by applying our understanding of light, matter, and motion to what we see, we are able to build a remarkably detailed picture of the physical properties of stars. As we take this first step beyond our local Solar System, we will

• Apply a form of stereoscopic vision, extended by Earth's orbit, to measure distances to nearby stars.
• Use the brightness of stars and their distances from Earth to discover how luminous they are.
• Use our knowledge of thermal radiation to infer the temperatures and sizes of stars from their colors.
• Measure the composition of stars from spectra.
• Study the orbits of binary stars and use Kepler's laws to calculate their masses.
• Classify stars, and organize this information on a plot of luminosity versus temperature, called the Hertzsprung-Russell or H-R diagram.
• Discover that 90 percent of the stars we see lie along a well-defined "main sequence" in the H-R diagram.
• Discover that the mass and composition of a main sequence star determine its luminosity, temperature, and size.
• Explore the range of stellar properties, learning how our Sun compares to other stars.

Organize

• Read Chapter 13 in your textbook or ebook.
• Take the Diagnostic Quiz to assess your understanding of the basic concepts and identify gaps in your understanding of the assigned reading.

Learn

• Access the Animations given for this chapter. These brief lessons enhance your understanding of core concepts.
  • Solar Spectrum Section: 13.3
  • H-R diagramSection 13.5
• Access the applets for this chapter.  Be sure to try different parameters with the applets to make sure you understand the concepts.
  • HR Explorer - change the luminosity and temperature (under Cursor properties) to see how the location of a star plotted on the H-R diagram will be affected. Be sure to choose the option to show the isoradius lines and luminosity classes.
  • Spectrum Explorer - choose absorption and select various elements to see how the appearance of spectral lines distinguishes stars of different spectral types.
• Use the FlashCards to test your memory for new terms.
• Work the "Thinking about the Concepts" and "Applying the Concepts" questions in the end of chapter review materials.
• If your instructor has assigned SmartWork online homework, login from the right navigation pane for additional practice and review.
• If your instructor has assigned Math Tools, be sure to study Math Tools Box 13.1, The Magnitude System, and 13.2, Using a Celestial Bathroom Scale to Measure the Masses of an Eclipsing Binary Pair.

Connect

• 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.
• 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.

Links

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W. W. Norton & Company has been independent since its founding in 1923, when William Warder Norton and Margaret D. Norton first published lectures delivered at the People's Institute, the adult education division of New York City's Cooper Union. The Nortons soon expanded their program beyond the Institute, publishing books by celebrated academics from America and abroad. By mid-century, the two major pillars of Norton's publishing program—trade books and college texts—were firmly established. In the 1950s, the Norton family transferred control of the company to its employees, and today—with a staff of 400 and a comparable number of trade, college, and professional titles published each year—W. W. Norton & Company stands as the largest and oldest publishing house owned wholly by its employees.