"When Venetia Burney's grandfather reads aloud from the newspaper about a new discovery--a "ninth major planet" that has yet to be named--her eleven-year-old mind starts whirring. She is studying the planets in school and loves Roman mythology. "It might be called Pluto," she says, thinking of the dark underworld. Grandfather loves the idea and contacts his friend at London's Royal Astronomical Society, who writes to scientists at the Lowell Observatory...