Here's a summary of the actual definition

Here is a summary of the IAU committee's actual definition of a "planet-" the first in history since the ancients simply coined the term to describe an object which moved against the background of the stars.

The high points:

1) The object must orbit a star- but not be itself a star;

2)) The object must have sufficient mass to be round, or nearly round;

3) The object must not be a moon (to answer Eric Phillips' question, in view of the fact that Pluto and Charon orbit each other, Charon is no longer to be considered a moon of Pluto, and the Pluto/Charon system has been redefined as a double planet).

Says committee member Richard Binzel, "Our goal was to find a scientific basis for a new definitition of 'planet,' and we chose gravity as the determining factor. Nature decides whether or not an object is a planet."

The downside to the definition: dozens of other objects may qualify- and 2003 UB313 discoverer Michael Brown suggests that the new definition- which he summarizes as "No Iceball Left Behind-" will quickly raise the total number of planets in our solar system to 53, and will ultimately boost it beyond 100. There are just too many round Kuiper Belt Objects out there!

I have a hunch that the recommendation may not pass the IAU General Assembly next Thursday. As elegant, on one level, as the definition is (it's essentially the one I myself supported before the recommendation was released), the practical consequence will be to crowd our solar system so full of "planets" that the concept will cease to be particularly meaningful.