Washington, Aug.16 : Supporters of Pluto are fighting to restore its title, but others say it's time to move on.
The current 8-planet system versus the 13-planet system-which would include Pluto-was the subject of a boisterous debate Thursday at the "Great Planet Debate: Science as a Process" conference at the Johns Hopkins Applied Physics Laboratory near Columbia, Maryland.
The International Astronomical Union (IAU)'s new definition of a planet rejects some rightful planetary members, said Mark Sykes, director of the Tucson-based nonprofit Planetary Science Institute.
But Neil deGrasse Tyson, an astrophysicist with the American Museum of Natural History and host of the PBS TV program NOVA Science Now, argues that the very word planet should be replaced with a wider term that captures the diversity of celestial objects that orbit stars.
"I'm saying define it however you want," he said, "then recognize how useless it is."
The debate stems from a decision by the IAU in 2006 to revisit the definition of a planet, which hadn't been changed since it was coined in ancient Greece, according to Tyson.
The organization voted that a planet must have three characteristics: orbit the sun; be big enough that its gravity makes it round, or nearly so; and have cleared its path of debris by flinging the debris with its gravity or absorbing it.
The IAU made a new category for Pluto, its moon Charon, and the giant asteroid Ceres. Those were called dwarf planets-the only difference being that they had not cleared their orbits of debris.
Besides a vocal public outcry about Pluto's demotion, scientists also lamented the decision based on both procedure and scientific integrity.
yson has called for an open-minded system of terms that will be applicable not only to our own solar system, but to the hundreds of so-called planets orbiting other stars.
Three terms: "terrestrials," "asteroids," and "jovials" for gas giants, would be a good start, he added.