Pluto is Not a Planet? That's Just Goofy

Pluto dodged a bullet today.

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would expand at a stroke the family of planets from 9 to 12 and leave textbooks and charts in thousands of classrooms out of date.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 Dr. Brown in 2005 orbiting far beyond Pluto in the outer solar system; and even Pluto's largest moon, Charon.

In addition, at least a dozen more solar system objects are waiting in the wings for more data to see if they fit the new definition of planethood, which is that an object be massive enough that gravity has formed it into a sphere and that it circles a star and not some other planet. The definition, they said, would apply both inside and outside the solar system.

The new definition was to be announced today in Prague, where some 2,500 astronomers are meeting in the triannual assembly of the International Astronomical Union. It is the work of the group's Planet Definition Committee, whose chairman is Owen Gingerich, a Harvard astronomer. The astronomers will vote on the definition on Aug. 25.

For several years now there has been a move to reclassify Pluto as something other than a planet. The Hayden Planetarium in New York City's Museum of Natural History (a must see attraction in New York) has clasified it as a "Minor Planet".

The planet (if that is what it is) has been an oddball ever since Clyde Tombaugh spied it wandering in the outer reaches of the solar system beyond Neptune in 1930. Not only is it much smaller than the other eight planets, only a fiftieth the mass of Earth, but its orbit is unusually elliptical and inclined to the plane that marks the orbits of the other planets. In recent decades, however, other objects with orbits like Pluto's have been discovered in the Kuiper Belt, a junkyard of icy debris beyond Neptune.

Many astronomers began to argue that it made more sense to think of Pluto as a Kuiper Belt object, a minor planet instead of a planet. When it was reported that the Hayden Planetarium had done just that in its new Rose Center, which opened in 2000, a firestorm erupted. Schoolchildren rushed to the defense of lonely little Pluto.

Now science will change as we learn more and as we explore the universe further. However, for my money, keep Pluto as a planet and don't expand the definition to be so inclusive that anything can be considered a planet. Maybe we need to form a coalition, 'Bloggers for Pluto'? I mean next thing you know they will tell us that the Sun doesn't revolve around the Earth, or that the moon really isn't made of swiss cheese.