The world’s astronomers, under the auspices of the International Astronomical Union (IAU), have concluded two years of work defining the lower end of the planet scale – what defines the difference between “planets” and “solar system bodies”. If the definition is approved by the astronomers gathered 14-25 August 2006 at the IAU General Assembly in Prague, our Solar System will consist of 12 planets: Mercury, Venus, Earth, Mars, Ceres, Jupiter, Saturn, Uranus, Neptune, Pluto, Charon and 2003 UB313. The three new proposed planets are Ceres, Charon (Pluto’s companion) and 2003 UB313. There is no change in the planetary status of Pluto, whom the New York Times essay described as ‘dodged a bullet’ this time.

Once the news came out on 16 August, both astronomers and the public immediately began to wrangle about it. Most of the supporters are happy to see that the Pluto may remain in the family of planets of the solar system, while some astronomers describe the new definition as “a mess”, expanding too much the boundary of the concept ‘planet’. At least 43 other publicly known objects in the Kuiper Belt were big enough to fit the planet definition, and that his group was sitting on a list of dozens more, said Alan P. Boss, a planetary theorist at the Carnegie Institution of Washington.

Definitions, of no matter what science disciplines, should always serve to clarify concepts and facilitate the discussion of future observations as well as the deduction of following theories. The new definition of planet unexceptionally falls in to this requirement. This is why IAU has to work for 2 years for a new definition for the word planet. Therefore, it is absurd trying to adjust the definition for any compromise like saving Pluto in the list other than the sake of science.