Book excerpt: When the International Astronomical Union (IAU) adopted a new definition of a "planet" in August 2006, Pluto became a dwarf planet, drawing a divisive line in science and public opinions. The controversy of whether Pluto is a planet continues years later, and passion about the decision remains, pitting scientist against scientist and invoking sentiments and nostalgia from the rest of the world. With the IAU definition, the future of space objects is forever changed. Learn how this resolution came to be and what it means for astronomy, who implemented it and who is against it, and whether it's the first or millionth time the world's view of astronomy has rotated on its axis. Written by an astronomer and educator who voted for the IAU resolution—Laurence A. Marschall—and a NASA scientist who supported the opposing petition that resulted—Stephen P. Maran—Pluto Confidential leaves no perspective out and no asteroid unturned in the Pluto debate. A telescopic look inside the book: • History of planetary disputes, including why Jupiter almost wasn't acknowledged • What Bode's Law is and how it has influenced observations • Who discovered Pluto and how it was named • The Kuiper Belt and its role in what it means to be a planet • Beyond Pluto and the eight distinguished planets