The IAU, from New Worlds to Exoworlds: recollections of a mandate

This paper presents my own recollections of the difficult relations that existed between the IAU and a fraction of the public, especially in the USA, following the IAU decision to reclassify Pluto as a dwarf planet at the 2006 General Assembly in Prague, and which ultimately led the IAU to organize the NameExoWorlds international contest to give public names to selected exoplanets and their host stars. In spite of the success of the International Year of Astronomy in 2009, the Pluto controversy continued, and its consequences climaxed during my term (2012-2015), as NASA's New Horizons probe approached Pluto for a flyby just before the 2015 General Assembly in Honolulu. It was during this period that the IAU launched the NameExoWorlds contest, which also came to a conclusion in Honolulu after over half a million votes were cast from all over the world. While the inside story of how the contest was organized has appeared elsewhere, here I focus on the historical and sociological context that made Pluto such a sensitive issue, especially in the USA, explaining why this contest generated another controversy between the IAU and the New Horizons team. However, after the world-wide success of NameExoWorlds, the IAU and the New Horizons team eventually reached an agreement on finalizing the characterization and names of a number of newly discovered Pluto and Charon surface features (an on-going process), while a new edition of NameExoWorlds is in preparation for the IAU centennial in 2019.