Yesterday, around 500 astronomers at the 26th General Assembly in Prague voted for a new definition of the celestial bodies in our solar system. There are three distinct kinds of objects in our solar system (excluding the satellites or moons). The three kinds of objects are:

1. Planets
2. Dwarf planets
3. Small solar-system bodies

In group (1) we find the four terristial planets (they have a solid surface: Mercury, Venus, Earth, and Mars) and the four gas planets (Jupiter, Saturn, Uranus, and Neptune). In group (2) we find dwarf planets like Ceres, Pluto (with its moon Charon), and 2003 UB₃₁₃. Group (3) comprises the comets, asteroids, Trojans (mainly sharing the orbit of Jupiter but also four are currently known in the orbit of Neptune), and a multitude of Kuiper belt objects (some are very likely "dwarf planets").

As a new member of the IAU I voted for the new resolution 5A+B, thus degrading Pluto to being a dwarf planet. I am sure that in the near future we will have a new resolution that will comprise all known planets -- not just the planets in our solar system. Today almost 200 such exo-planets are known with masses from several Jupiters to a few times the Earth. Already in November 2006 the French/European satellite mission COROT will be launched. The aim of COROT is to discover new "super-Earths" around nearby stars. In 2008 the NASA Kepler satellite mission will fly and it is expected that several true Earth-like planets will be discovered.