This Friday marks the 75th anniversary of the discovery of Pluto. Since its discovery by an amateur astronomer, the question of what exactly Pluto is has raged. Five years ago, for instance, the head of the Hayden Planetarium and American Museum of Natural History officially demoted Pluto from planet to merely one more of the ring of comets and other junk at the outer reaches of the Solar system. His reward? "[H]ate mail from third-graders." I vote for keeping Pluto taken down a notch, if only to preserve the accuracy of Holst's The Planets.