The great (and sometimes serious) debate about Pluto

LAUREL, MD -- The entrance to the debate over Pluto's planet status said it all: With techno music blaring in the background, the two debaters and a moderator walked into the auditorium, cameras flashing and the audience clapping.

One debater, Neil deGrasse Tyson, did the boxing entrance à la Rocky. That's how hot the matchup is between Pluto as a planet and Pluto as a plutoid.

Tyson, director of the American Museum of Natural History's Hayden Planetarium in New York, supports the demotion of Pluto. In the other corner, Mark Sykes, director of the Planetary Science Institute in Tuscon, Ariz., does not agree with the recent ruling that essentially booted Pluto from the planet lineup.

The debate over whether Pluto should be considered a planet is part of "The Great Planet Debate: Science as Process" conference here at the Johns Hopkins University Applied Physics Laboratory (APL) that runs through Saturday.

Before the idea-throwing began, debate moderator Ira Flatow of National Public Radio's Science Friday threw out his own rule, "No throwing of perishable items or missiles of any kind at the stage," Flatow said with a smirk.

In fact, the debate was filled with lots of applause, laughter and some snide remarks, but mostly it was a friendly tussle. In fact, neither Tyson nor Sykes clearly defined their specific positions on Pluto and the definition of a planet.

How many planets?

In general, Tyson said astronomers need to come up with an entirely new lexicon to group planets and planet-like objects together. He also said Pluto is not like the other eight major planets in the solar system and that it instead fits into the Kuiper Belt, a vast region of objects beyond the orbit of Neptune.

"And I am certain Pluto is happier there," Tyson said.

Sykes said that if a non-stellar object is massive enough to be round and it orbits a star, it ought to be a planet. Under this definition, the solar system would have 13 planets, although more might be found in the future beyond the orbit of Pluto. In addition to Pluto and the other eight major planets, these would also include Ceres, Pluto's moon Charon, Eris, and recently discovered Makemake.