Scientists downgrade Pluto
Pluto was demoted to 'dwarf planet' last week.
Published Aug. 29, 2006
It seems scientists have answered the age-old question of whether it's just size that matters.
In recent years, Pluto has received quite a large amount of attention for one very specific reason: Scientists debated whether to consider it as a planet. Now, they've made their decision.
MU Astronomy professor Angela Speck said she agrees with changing Pluto's status from planet to dwarf planet.
"When Pluto was discovered, it was all alone," Speck said in an e-mail. "Now it is clear that it is just one of many similar bodies that exist in that part of the solar system. Most astronomers have accepted the demotion for several years now. It is only nostalgia for Pluto's planet status that has kept it a planet for so long. There may also be a contributing factor in the fact that Pluto was discovered by an American."
The Kuiper Belt, an asteroid belt lying slightly beyond Pluto and about 10 billion miles from the sun, has caused scientists not only to question Pluto's origins but also the definition of a planet because further investigation into the Kuiper Belt has revealed celestial bodies large enough to be considered planets.
"We don't actually have a definition for planet, and now we need one," Speck said in an e-mail before the International Astronomical Union set the new definition that ruled Pluto out.
In late August, the IAU was prompted to meet in Prague to discuss planet definitions and Pluto's future. IAU member Jay Pasachoff, who attended the forum in Prague, said Pluto should be considered a planet based on its atmosphere instead of being denied planetary status because of its mass or orbit.
"I'd like to keep Pluto as a planet, sort of grandfathering it in," Pasachoff said in an e-mail. "I have been studying Pluto's atmosphere, and it joins the eight planets inside its orbit, except for Mercury, whose atmosphere has been expelled by global warming. So I wish we could define planet as round-ish objects that have or had atmospheres."
After Pasachoff attended the forum, scientists came to a conclusion.
"The main change of the day was to put 'dwarf planet' in quotes to make it clear that we were defining the pair of words together," Pasachoff said. "Both planets and dwarf planets orbit the sun and have enough gravity to make them round."
Later in the day, opinion shifted about whether dwarf planets and classical planets were the same thing.
"An attempt to make the category of 'dwarf planet' parallel to that of classical planet failed," Pasachoff said. "It was made clear that dwarf planets are not planets. The answer to the question, 'Is Pluto a planet?' is 'no.' One could say, 'No, but it is a dwarf planet.'"
Owen Gingerich, chair of the Planet Definition Committee at IAU, also attended the IAU forum and expressed his displeasure of the final decision regarding planet definition.
"While the process was a democratic process, it was a flawed process," he said.
Upon further scrutiny, Gingerich said, the planet definition unravels and there is still a certain amount of confusion among astronomers.
"As far as the definition goes right now, it leaves quite a bit to be desired," he said.
