January 29, 1999
Steve Shawl received the letter by e-mail. The issue that provoked it is that the International Astronomical Union, or IAU, is debating whether Pluto should keep its status as a planet.
Shawl, a University of Kansas professor of physics and astronomy, forwarded the letter to Brian Marsden, who heads the IAU's Minor Planet Center.
In his reply, Marsden assured the former citizen of Streator that Pluto would remain a planet -- but also be recognized as a transneptunian object. There are about 90 such asteroid-sized objects located on the outer fringes of the solar system.
Pluto, it turns out, is an odd little ball. It's only about 1,450 miles across -- the distance, more or less, from Kansas City, Mo. to Las Vegas.
Moreover, it represents a break from a planetary trend. While the inner planets of the solar system, out to Mars, are basically orbiting rocks, the outer ones are gigantic gas balls -- until you come to Pluto.
If you drilled toward the center of Pluto, you'd be boring through ice the first quarter of the way. But you wouldn't want to make a margarita out of the frozen nitrogen, carbon monoxide and methane you'd be drilling through.
Currently, Pluto's got a thin atmosphere, but that's only because it's as close to the sun as it ever gets. The heat is changing some of the ice into gas.
Pluto orbits the sun every 248 years, moving in a more pronounced ellipse than the other planets. That means that for about 20 of those 248 years, it's closer to the sun than Neptune is.
Another oddness is that Pluto doesn't orbit within the same plane as the other planets.
Despite Pluto's eccentricities, the astronomers I talked with think this whole challenge to Pluto's planethood is overdone. "Much ado about nothing," Shawl says. David Tholen, a KU graduate now at the University of Hawaii, adds, "Debating the dividing line between planet and minor planet (or asteroid) is like debating the dividing line between city and town, river and stream."
Yet for some the debate has an emotional edge. The response of the former Streator resident rests in part on the fact that Clyde Tombaugh, who discovered Pluto, was born near Streator. KU also has an emotional stake in this debate. Tombaugh went to school here, and a campus observatory bears his name.
But there's something deeper than local pride at work. When cherished beliefs fail, people get nervous. The strange and unpredictable behavior of Bill Clinton and the U.S. Congress, coupled with the surprising response of the American public to it all, has made a lot of people anxious and for many different reasons. It's no wonder that challenges to Pluto's identity are making people edgy.
An editing professor of mine used to say, "If your mother tells you that she loves you, check it out." A truth for our times, no doubt about it.
Story by Roger Martin