Space and planets are topics of endless fascination to kids and part of every grade-school curriculum. Yet because of the history-making reassignment of Pluto from “planet” to “dwarf planet” on August 24, 2006, all books on the solar system are now out of date. Enter When is a Planet Not a Planet? The Story of Pluto by Elaine Scott, an esteemed writer of non-fiction for children. Scott is the first to put the answer to the title question into terms simple enough for a very young audience to understand, based upon the new definitions determined by the International Astronomical Union. Well-researched and accompanied by large, awe-inspiring photographs and paintings, this exciting new book makes clear what astronomers have argued about for decades.