| The Milky Way Galaxy | 445 |
| 15.1Discovering the Milky Way | 447 |
| Shape of the Milky Way | 447 |
| Size of the Milky Way | 448 |
| 15.2Overview of the Milky Way | 450 |
| Structure and Contents | 450 |
| Mass of the Milky Way and the Number of Stars | 451 |
| Age of the Milky Way | 452 |
| 15.3Stars of the Milky Way | 452 |
| Stellar Censuses and the Mass Function | 452 |
| Two Stellar Populations: Population I and Population II | 453 |
| Star Clusters | 455 |
| 15.4Gas and Dust in the Milky Way | 457 |
| Interstellar Dust: Obscuration and Reddening | 458 |
| Interstellar Gas | 460 |
| Visible Emission from Interstellar Gas | 460 |
| Radio Waves from Cold Interstellar Gas | 462 |
| Extending Our Reach: Mapping the Milky Way with Radio Waves | 462 |
| 15.5Motion of Stars and Gas in the Milky Way | 463 |
| 15.6Measuring the Milky Way | 466 |
| Diameter of the Milky Way | 466 |
| Mass of the Milky Way | 466 |
| Extending Our Reach: Measuring the Mass of the Milky Way | 467 |
| Extending Our Reach: Measuring the Sun's Speed Around the Milky Way | 469 |
| 15.7The Galactic Center | 469 |
| 15.8History of the Milky Way | 471 |
| Formation of Our Galaxy | 471 |
| Collapse of the Proto-Milky Way and the Birth of Population I and II Stars | 471 |
| Population III | 474 |
| The Future of the Milky Way | 474 |
| Project | 477 |
2002 McGraw-Hill Higher Education