The world's astronomers on Tuesday passionately debated a plan to use roundness as the criteria for defining a "planet," with some experts calling the proposal "reasonable" but others declaring it "bound to fail." Pluto would qualify as a "dwarf planet" distinct from the solar system's eight "classical planets" under the definition presented by a panel at the International Astronomical Union (IAU) conference in Prague. Yet the special panel also recommended the eight bodies from Mercury to Neptune share the general term "planet" with Pluto and other "trans-Neptunian objects" because they orbit a star and meet gravitational criteria for "hydrostatic equilibrium," which makes them "nearly round." Moreover, the panel suggested calling Pluto and its space companion Charon a "double planet." In a non-binding show of hands after a 90-minute debate, IAU members voted "about 50-50" in favour of the proposal's main resolution, said IAU spokesman Lars Christensen. But "a clear majority" opposed two other resolutions. "But this was just a gauge" before a final conference vote Thursday, Christensen said. Pluto has been honoured as the ninth planet since its discovery in 1930. Scientists were forced to reconsider its status - and the very definition of a planet - after the 2003 discovery of a larger and more distant object circling the sun called UB313. Although Pluto's future has captured public attention since the IAU started working on the issue two years ago, most scientists commenting from the conference floor Tuesday focused on technical issues. Some spoke passionately about the proposed definition's impact on scientists searching for star-orbiting objects outside our solar system. --More
