The recent demotion of Pluto from planetary status caused a worldwide uproar – the smallest planet turns out to have legions of devoted fans. But in 1930, when Clyde Tombaugh found the image that would turn out to be Pluto, the history of this elusive body was already surrounded by mystery, obsession, and controversy. Michael Byers' new novel about the discovery of Pluto, Percival's Planet, based on archival research and a careful reconsideration of the historical facts, suggests that even those closest to the discovery had reason to suspect that what they'd found wasn't exactly a planet after all.  Michael Byers will discuss his novel and Bruce Greenway, an astronomer and computer scientist who personally knew Clyde Tombaugh, will discuss the 2006 International Astronomical Union definition of Planet and the resulting demotion of Pluto.