EYEPIECE Journal of the Amateur Astronomers Association of New York April 2009 Volume 57, Number 4, ISSN 0146-7662 Asimov Panelists Probe the Def inition of a Planet By Thomas Haeberle As the International Astronomical Union (IAU) prepares to meet in August in Brazil, scientists are still brawling over what's a planet. ... Tyson questioned the motivation of slogans used for the New Horizons mission to Pluto, such as "The f irst mission to the last planet." ... They were looking for planets." ...