IAU General Secretary Dr. Karel A. van der Hucht IAU - UAI Secretariat 98-bis Blvd Arago F–75014 PARIS FRANCE On August 24, 2006, your organization defined the term “planet” for the first time. Nevertheless, the term had already been defined (and in common use) since shortly after Pluto’s discovery, in 1930. By reclassifying Pluto, your organization acted inappropriately; reclassification was a mistake for several reasons. First, Pluto has been identified as a planet for 70 years, and as popular culture attests, Pluto has long been a welcome, if distant, neighbor in the solar system. In short, Pluto is popular planet. A term’s general popularity is generally unimportant; nevertheless, in this case, it is of paramount importance. That is to say, this isn’t simply a scientific issue; this is also a debate about language. In our view, language is public property. For most of the world, the word “planet” has already been defined. For the IAU to redefine the term arbitrarily, without the consent of the general public is inconsiderate, confusing and counterproductive. For all practical purposes, the redefinition is obligatory, for specialists and the general public alike. The IAU states that this isn’t the case, but it is; textbooks are being rewritten, children are being re-taught. The IAU has therefore presumed to be the arbiter of public language, and it’s this assumption that has made the IAU’s decision wildly unpopular. To be sure, language is arbitrary in a sense, but the public is the final arbiter. To think otherwise is presumptuous. In addition, it seems there are other options besides reclassifying Pluto. As we understand it, the problem with classifying Pluto as a planet is this— one will likely have to classify other objects as planets as well. This, some argue, will lead to a confusing and cluttered solar system. Nevertheless, many argue that the more, the merrier. Furthermore, this problem can likely be avoided. For instance, if we define the term “planet” to include objects of Pluto’s size (and of Eris’s) and larger, then we’ll simply have one more addition (plus Pluto) to the celestial family. If objects are found that are larger than Pluto, we could add those too. What harm would this do Some will argue that this is arbitrary, and we’ll whole-heartedly agree, but definitions often are. The important point, however, is to find a definition that all parties can agree to; thus far, the IAU has not made that effort. For this reason, the IAU should consider the public’s wishes at the upcoming IAU conference and reclassify Pluto as a planet. With Respect,

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