Many researchers were none too happy when the International Astronomical Union (IAU) voted in 2006 to cast Pluto out from among the planets, demoting it along with similar bodies in the solar system to the status of mere dwarf planets.

Some of them would still like to reverse that decision, or at least convince the public that the IAU process did not reflect the give and take of workaday science. Hence "The Great Planet Debate: Science as Process," a three-day conference under way right now at The Johns Hopkins University Applied Physics Laboratory (APL).

As I write, conference co-organizer and vocal Pluto booster Mark Sykes, director of the Planetary Science Institute, Tucson, Arizona, is set to duke it out this afternoon in a public debate with dwarf planet-proponent Neil deGrasse Tyson, director of the American Museum of Natural History's Hayden Planetarium in New York.

Sykes is promoting the view that a planet should be construed as any object in the solar system massive enough to have adopted a round shape. He says the solar system should contain 13 planets by this definition, including Ceres, the largest asteroid between Mars and Jupiter.

The IAU definition excludes round bodies that haven't swept their orbits clear of smaller rocks. Tyson heralded this rezoning in 2001 when he excluded Pluto (above) from the a display of planets at the museum.

Will the conference accomplish anything? The IAU seems unphased: It announced in June that dwarf planets past Neptune's orbit would now be known as plutoids. Some researchers think rekindling the Pluto debate in itself gives the wrong impression about how science is done.

“No votes will be taken at this conference to put specific objects in or out of the family of planets,” APL's Hal Weaver, a conference organizer, said in a press release. “But we will have advocates of the IAU definition and proponents of alternative definitions presenting their cases.”

Tyson has indicated there's a chance that working astronomers could still adopt a new definition. "If a new consensus emerges it will easily overturn the IAU," he told

Those who registered can view a live webcast of the debate on the conference web site. Everyone else will have to wait until they post it online.

Related: What Is a Planet?

Image credit: Eliot Young (SwRI) et al., NASA