STOCKS GET THROWN off the S&P 500 and socialites get knocked off the A list, but never in the history of the solar system has there been a demotion like this: astronomers are taking steps to delete Pluto from the list of planets. No, the smallest and (usually) most distant of the nine planets, discovered in 1930, hasn't decamped to Alpha Centauri. Rather, some astronomers believe that Pluto never deserved to be ranked with the likes of Jupiter, Saturn and Earth in the first place. As soon as this week or as late as this spring, the International Astronomical Union is expected to vote to reclassify Pluto as a ""minor planet,'' of which there are close to 10,000. Or it could be reclassified as a ""trans-Neptunian object,'' or TN-1. That's a fancy way of saying Pluto is just another icy rock in the sea of asteroids beyond Neptune called the Kuyper Belt.
Pluto just doesn't fit the planetary mold. It's smaller than seven moons in the solar system, including Earth's. And while the orbits of real planets are almost circles, Pluto's is so goofy that it frequently swings closer to the sun than Neptune does. It is neither rocky like four planets nor gassy like the other four. The reclassification makes scientific sense and ""is not a demotion,'' insists Brian Marsden of the Harvard-Smithsonian Center for Astrophysics. ""It's an honor.'' Tell that to the legions of schoolchildren who have learned ""My Very Educated Mother Just Served Us Nine Pizzas.'' Or to astrologers: Pluto, the sign of disruption, rules Scorpio. If Pluto isn't a planet, then a lot of people have a different future.