Boulder scientist blasts back at Pluto-demoting definition

Jim Erickson, Rocky Mountain News

Published September 1, 2006 at midnight

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A Boulder planetary scientist and a Tucson colleague have collected 300 signatures from researchers around the world who oppose the International Astronomical Union's recently passed definition demoting Pluto as a planet.

The IAU definition, passed last week at a scientific meeting in Prague, cut the number of planets in the solar system from nine to eight. Pluto was relegated to the new category of "dwarf planet."

Planetary scientists Alan Stern, of the Southwest Research Institute in Boulder, and Mark Sykes, of the Planetary Science Institute in Tucson, launched a petition drive to express outrage at a definition that Stern on Thursday called "unworkable, technically flawed and sloppy." The signatures will be submitted to the IAU as a courtesy, but Stern and other planetary scientists are moving ahead without the group.

Stern said he and Sykes are organizing a meeting of up to 1,000 scientists. They will gather next year to pen "a workable definition that scientists can use in research papers, that can go into text books and educational Web sites," said Stern, lead scientist on NASA's $700 million New Horizons mission to Pluto.

The IAU is the international arbiter of issues related to astronomical nomenclature. Its resolution, passed Aug. 24, defines a planet as a celestial body that orbits the sun and is big enough that its self-gravity pulls it into a roughly round shape.

In addition, the object must have "cleared the neighborhood around its orbit" by sweeping up stray blocks of rock and ice.

Pluto doesn't meet the third requirement because it loops around the sun within the Kuiper Belt, a band of icy bodies beyond Neptune.

Also Thursday, the world's largest organization of planetary scientists issued a statement saying "future refinements" of the IAU definition "will almost certainly be desired."

"All definitions have a degree of fuzziness that requires intelligent application: What does 'round' really mean?' " the Division for Planetary Sciences statement noted.

The Stern-Sykes petition was signed by several Colorado scientists, including researchers at the University of Colorado, the University of Denver, the Southwest Research Institute, Boulder's Space Science Institute and the Denver Museum of Nature & Science.

The petition states, "We, as planetary scientists and astronomers, do not agree with the IAU's definition of a planet, nor will we use it."

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