Bowling Green, Ky. - The International Astronomical Union stripped Pluto of its planetary status Thursday, but a Western Kentucky University faculty member says the decision was made after a “long and lively debate” Tuesday.

Dr. Richard Gelderman, associate professor in WKU’s Physics and Astronomy Department, was among more than 2,000 astronomers who debated the issue during the IAU’s 26th General Assembly in Prague, Czech Republic. Dr. Gelderman returned to Bowling Green late Wednesday before the IAU’s final decision on a new definition of what is or isn’t a planet. 

“People were passionate on both sides of the issue,” Dr. Gelderman said of Tuesday’s debate. “It’s not that we don’t like Pluto. It just doesn’t fit the new criteria.”

The decision won’t change the way Dr. Gelderman teaches his astronomy courses at WKU. “Pluto has always been the odd man out,” he said. “I’ve always taught that there are four Earth-like rocky planets and four Jupiter-like gaseous planets and then there’s Pluto.”

The IAU, the world’s largest professional group for astronomers, spells out the basic tests that celestial objects will have to meet before they can be considered planets and join Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune.

Pluto will be reclassified in a category called “dwarf planets.” A third class of objects that orbit the sun, such as asteroids, comets and other natural satellites, will be called “small solar system bodies.”

“Pluto and other objects are not like the eight planets we’re familiar with so this gives them a new category,” he said. “For me, Pluto will just have a different name as a dwarf planet.”

The current debate was triggered by the discovery in 2003 of UB313, a large icy body in orbit around the Sun well beyond the orbit of Pluto. The debate has been whether this new object should be classified as a planet, and if not, whether Pluto, smaller than the new object, should still be included as a planet.

When Pluto was discovered in 1930, nothing else like it had been discovered so it was easy to add it to the list of planets, Dr. Gelderman said. “But now we believe there may be more than a dozen objects with the size and composition of Pluto,” he said.
More information on the IAU meeting is available online at www.iau.org

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