Pluto dodges a bullet

In the hope of ending years of wrangling, a committee of astronomers and historians has proposed a new definition of the word "planet" that would expand at a stroke the family of planets from nine to 12 and leave textbooks and charts in thousands of classrooms out of date.

But astronomers immediately began to wrangle about it.

"It's a mess," said Michael E. Brown of the California Institute of Technology.

Among the chosen few within the solar system would be not only Pluto, whose status has been challenged in recent years, but also Ceres, the largest asteroid; 2003 UB313, nicknamed Xena, an object discovered by Brown in 2005 orbiting far beyond Pluto in the outer solar system; and even Pluto's largest moon, Charon.