On Tuesday, August 22 at the International Astronomical Union Conference in Prague, the IAU Executive Committee will hold a general meeting to discuss the meaning of the concept of planet. As in an earlier post, the definition that has been proposed, and that will be discussed tomorrow has raised perhaps more questions than it answers. If you want a very good discussion of the “re-definition” of planet, go to the Wikipedia article. The article will change as the IUP makes its decision. You might also read this news bulletin on the re-definition of planet.

If the definition that has been proposed is approved, then the Solar System will consist of 12 planets. The new ones would be 2003 UB313, Charon and Ceres, as shown here (although not in the location shown).

Image: Proposed planets UB313, Charon, Ceres, next to Earth

If the astronomers approve the proposal, classroom Solar System mobiles will now consist of the following: Mercury, Venus, Earth, Mars, Ceres, Jupiter, Saturn, Uranus, Neptune, Pluto, Charon and 2003 UB313. The Discovery Store sells a remote control mobile!

Image: Remote controlled Solar System Mobile

Some other articles to read on the planet defintion include:

1. Planetary Scientists Support Proposed Redefinition of a Planets
2. Nine Planets Become 12 with Controversial New Definition
3. The IAU draft definition of “planet” and “plutons”
4. Planets plan boosts tally to 12
5. Proposal would increase planets from 9 to 12