How Many Planets?

The International Astronomical Union is meeting in Prague to decide the fate of several bodies in our solar system. A proposal on the table calls for a change from the current nine planets to a solar system consisting of eight planets, three plutons, and one very large asteroid. In the plan, Pluto becomes a pluton, along with its neighbor Charon and the planetoid UB313. Between Mars and Jupiter the scientists add the asteroid Ceres (diameter 950 km or 590 miles) to the standard definition of the solar system. BBC news provides an overview but About.com's Space site covers the topic in-depth.