Chapters in this book

1. Frontmatter i
2. Contents vii
3. Preface ix
4. 1. What Is a Planet? 1
5. 2. Seven Perfect Planets Made of Aether 6
6. 3.The Earth Becomes a Planet 36
7. 4. Sixteen Planets 59
8. 5. Not Everything That Orbits the Sun Is a Planet 71
9. 6. Uranus! 82
10. 7. The Celestial Police 95
11. 8. Neptune, the Thirteenth Planet 107
12. 9. Easy Come, Easy Go 121
13. 10. Pluto, the Fourth Ninth Planet 130
14. 11. Hidden Secrets of the Outer Solar System 148
15. 12. The Plutinos 167
16. 13. Is Pluto a Planet? 179
17. 14. Goldilocks 185
18. 2006 Postscript. Current Thoughts by Other Astronomers 222
19. 2008 Postscript. The Post-2006 Status of Pluto 232
20. Appendix. What We Know about Pluto 243
21. Notes 253
22. Index 261