The International Astronomical Union proposes to end the debate over what is and isn't a planet by creating a new two-part definition: the body must orbit a star, and it must be sufficiently large to be forced into a spherical shape by gravity. Read the full story on Space.com.

There's much debate over this proposal however, as it turns Pluto's moon into a planet (actually, the pair end up as a double planet) but giant moons that dwarf Pluto but orbit larger worlds (like Earth's moons, or Jupiter's Galileo satellites) would still be moons. The definition would also mean that the asteriod Ceres would now be considered a planet, as would the newly discovered Kuiper Belt object informally called Xena. The formal name of these diminutive orbs would be "plutons", but they'd still be considered planets, and there could be a lot of them. One estimate says we could end up with as many as 24 planets in the solar system if the IAU goes with this definition.