Solar system could grow to 12 planets: Astronomers propose adding 3 tiny bodies to the list -- and keeping Pluto

PRAGUE, Czech Republic -- Our solar system would have 12 planetsinstead of nine under a proposed "Big Bang" expansion by leadingastronomers, changing what billions of schoolchildren are taught.

Much-maligned Pluto would remain a planet -- and its largest moonplus two other heavenly bodies would join Earth's neighborhood --under a resolution to be presented today to the InternationalAstronomical Union, the arbiter of what is and isn't a planet.

"Yes, Virginia, Pluto is a planet," quipped Richard Binzel, aprofessor of planetary science at the Massachusetts Institute ofTechnology.

The proposal could change, however: Binzel and the other nearly2,500 astronomers from 75 nations meeting in Prague to hammer out auniversal definition of a planet will hold two brainstorming sessionsbefore they vote on the resolution next week.

But the draft comes from the IAU's executive committee, which onlysubmits recommendations likely to get two-thirds approval from thegroup.

Besides reaffirming the status of puny Pluto -- whose detractorsinsist it shouldn't be a planet at all -- the new lineup wouldinclude 2003 UB313, the farthest-known object in the solar system andnicknamed Xena; Pluto's largest moon, Charon; and the asteroid Ceres,which was a planet in the 1800s before it got demoted.

A dozen more planets soon?

If the resolution is approved, the 12 planets in our solar systemlisted in order of their proximity to the sun would be Mercury,Venus, Earth, Mars, Ceres, Jupiter, Saturn, Uranus, Neptune, Pluto,Charon, and the provisionally named 2003 UB313.

UB313's discoverer, Michael Brown of the California Institute ofTechnology, nicknamed it Xena after the warrior princess of TV fame,but it likely would be rechristened something else later.

The galactic shift would force publishers to update textbooks, andschool teachers to rejigger their planet mobiles.

Outside the realm of science, astrologers accustomed to makingpredictions based on the classic nine might have to tweak theirformulas.

Even if the list of planets is lengthened when astronomers vote onAug. 24, it's not likely to stay that way for long: The IAU has a"watchlist" of at least a dozen other candidates that could becomeplanets once more is known about them.

"The solar system is a middle-aged star, and like all middle-agedthings, its waistline is expanding," said Jack Horkheimer, host ofthe "Stargazer" TV show.