Officials with the National Astronomical Observatories of Chinese Academy of Sciences (NAOC) revealed that the International Astronomical Union (IAU) General Assembly is to be held in Czech Republic in August this year and will give answers to whether or not there is a 10th planet in the solar system and whether or not Pluto, the 9th planet, belongs to the solar system, which are two fiercely debated issues in the astronomical community in recent years. During the meeting, over 2,000 astronomers from all over the world, including China will cast votes on a complete scientific definition of "planet" which is closely related to the family membership of the solar system.

Li Jing, a researcher in NAOC said in an interview that Mike Brown, an American scientist discovered a celestial body on the verge of the solar system in 2003 and declared it is the 10th planet in the solar system in 2005. The announcement sparked off heated debates over the existence of the 10th planet and the validity of Pluto's membership in the solar system, which has reasonably become the discussion topic for this year's IAU General Assembly. A subcommittee of IAU will prepare a formula for the definition of planet. The formula will be handed to the conference, and discussed and approved by the astronomers through voting. The astronomers' decision will give clear answers to how to define a "planet" and how many planets there are in the solar system.

According to Li Jing, most of Chinese astronomers and part of their foreign counterparts do not think the so-called 10th planet "Xena" and even Pluto are true planets. These two celestial bodies do not follow the rules of planet. Instead they are objects inside the Kuiper Belt that is vast population of ice bodies extending beyond the orbit of Neptune. Thus in fact, the solar system contains only 8 planets. But in as early as 1930, Pluto was put into textbooks as the 9th planet in the solar system. For this historical reason, it is very unlikely that Pluto will be deprived of its membership in the solar system family. But those celestial bodies discovered recently or to be found in the future inside the solar system will not be called planets by any name if they do not fit the scientific definition of "planet". Nevertheless, some astronomers think that "Xena" is the largest object found beyond the orbit of Pluto and qualifies as the 10th planet because of its size.

By People's Daily Online