, to a lowly dwarf planet. The bitter debate over the change is set to continue later this summer.)
PLUTO (ONCE AND FUTURE PLANET?): In 2006 an international group of astronomers demoted the ninth planet, Pluto (shown here with its moon Charon), to a lowly dwarf planet. The bitter debate over the change is set to continue later this summer.
Image: NASA
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Pluto lovers, don't despair: Researchers have not given up the fight for the former ninth planet. Many of them put up a fuss two years ago when the International Astronomical Union (IAU) downgraded Pluto to the status of mere dwarf planet. Now they plan to revive the debate, this time under the banner of public understanding of science.
Researchers on both sides of the issue are set to gather in August at Johns Hopkins University Applied Physics Laboratory in Laurel, Md., for what's being called "The Great Planet Debate: Science as Process." The goal, says the conference's co-organizer Mark Sykes, director of the Planetary Science Institute in Tucson, Ariz., is to teach the public that science is a process of constant revision and refinement. "People should be exposed to that process," he says. "The IAU process gave the impression that science is done by a bunch of scientists voting behind closed doors."
The schedule for the upcoming conference includes back-to-back talks on the current IAU definition of a planet (a round body that has cleared its orbit of competitors) as well as an earlier version, preferred by researchers such as Sykes. Also listed is a talk on "challenges and opportunities" for teachers, who are invited to attend. "One of the problems over the last couple of years," Sykes says, "has been [that] teachers have been confused what to teach"
The lingering resistance to the IAU's decision irks some researchers. "I think fighting it is doing more damage to our reputation than anything," says Harold Levison, a planetary scientist at the Southwest Research Institute in Boulder, Colo. He agrees with the IAU's conclusion, he says, but adds that he would have rather seen planets divided into two groups: major and minor. The IAU could still decide to revisit the subject in a meeting scheduled for next year.
Despite the rift, textbook publishers seem to be taking Pluto's demotion in stride. Some contacted by ScientificAmerican.com say they anticipated it. An early draft of Perspectives on Astronomy (first edition, 2007), written before the August 2006 IAU meeting, excluded Pluto from a map of the planets in the solar system, says text co-author Dana Backman, a planetary scientist at NASA Ames Research Center, Moffett Field, Calif.
"The IAU decision was expressing what we already believed, and had put words to paper about," Backman says. He provided an excerpt of the published first chapter by e-mail, which briefly recounted Pluto's demotion but did not describe it as controversial.
Planetary Sciences (first edition, 2001) counted Pluto among the planets but will exclude it in the second edition, due out in 2009, according to Backman's fellow Ames researcher Jack Lissauer, co-author of the text, who shared the 2007 Chambliss Astronomical Writing Award from the American Astronomical Society with co-author Imke De Pater.
Pluto has always stood out from the other planets. At roughly a fifth the mass of the moon, it is the largest of the icy bodies that make up the Kuiper belt beyond Neptune's orbit. Unlike the four inner (terrestrial) planets, it has a tenuous atmosphere at best.
The outer four Jovian planets are massive and gaseous. None resemble the former ninth planet, which also has a distinctly eccentric, or elliptical, orbit that crosses that of Neptune. "When you look at a plot like that [of eccentricity], there's eight planets," Levison says. "It just jumps out and bites you in the butt."
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9 Comments
Add CommentSimple, give Pluto dual rights as a regular planet and a dwarf planet. Any new planetiod should be bigger than than the largest moon in the solar system. This debate could go on for years...
Reply | Report Abuse | Link to thisI've always hated the "dwarf planet" designation as a *distinct* category from 'planet'. Is a hybrid automobile not an automobile? Is a tropical fruit not a fruit? It is much more logical to use a more inclusive definition of 'planet', with the 'major' and 'minor' sub-categories.
Reply | Report Abuse | Link to thisAs fond as I am of Pluto, the point of the scientific method is to 1) theorize, 2) test/challenge the theory, 3) revise the theory, and 4) goto step 2.
Reply | Report Abuse | Link to thisSaying we should refrain from revising our planetary definitions/categorizations because we are fond of Pluto as a planet is closer to dogma than science.
I see this as an opportunity to teach the value and purpose of the scientific method, not to be upset that change happened.
Hmmm... Pluto, a planet, not a planet. The first question that comes to my mind is, "what difference does it make?" If the classification applied to objects in space causes you significant upset, you probably have few concerns in your life. Or, your priorities need a serious re-think. I doubt that Pluto is offended over its naming. I don't think that rekindling the debate is either a good or bad idea - it is a pointless idea. Put it this way, if life had never evolved on this planet, Pluto wouldn't even have a name. Poor planet... or dwarf planet... or... Oh, who bloody cares!
Reply | Report Abuse | Link to this> As fond as I am of Pluto, the point of the scientific
Reply | Report Abuse | Link to this> method is to 1) theorize, 2) test/challenge the
> theory, 3) revise the theory, and 4) goto step 2.
>
Agree. However, if we are revising it we should do it with a better logic than before, right? Or what's the point?
The new definition is ambiguous at best: it, for example, excludes Nepune from the planets category too. Pluto has not been cleared from its orbit, so away with Neptune too?
I understand it all came from the discovery of Eris... what's wrong ten planets? We define things based on arbitrary points of refference (for the most part) like water's freezing temp or Earth's circumference. Wouldn't it be much more simple and unambiguous to just say "any round object equal or greater in size than Pluto" is a planet? Why the heck not? WE define the refference. The new definition does not exclude the moon as a planet, did you notice?
On the personal side, I think it is much more fun and exciting the discovery and addition of new planets to the family than demoting the classical ones.
Wouldn't a better definition of a planet be "any body that has enough mass to ensnare or entrap other bodies in an orbital motion around them".
Reply | Report Abuse | Link to thisPluto has a moon, so, I would think, should be considered a planet. Some debate over whether it is simply in a twin orbit with it's moon could be made, but so could the earth/moon relationship. Every planet has a somewhat eccentric and wobbly orbit around it's gravitational anchor.
I guess my point is.. if you go to a point equidistant from our galaxy and the nearest known galaxy, and find some rocks floating in space, if they share some sort of cyclical orbit around eachother, they have enough mass to support that attraction. At that point they are a planetary system.
If you add a burning mass to the center of the system.. now you have a solar system with it's planets.
Take a bunch of solar systems and planetary systems and swirl them around a gravitational center (black hole perhaps), and you have a galaxy.
The IAU should have not voted to demote Pluto with so few members voting, Therewas an outcry of members not at the conference that would have never demoted Pluto. The vote should be dismissed,
Reply | Report Abuse | Link to thisIt is interesting how supporters of Pluto's demotion always come back to claiming that supporters of Pluto's planetary status come to their conclusions based on emotion. This argument is nothing but a straw man. The fact is, four percent of the IAU made the decision to demote Pluto. The other 96 percent had no say because no absentee voting was allowed. So one can reasonably contest the claim that scientists as a whole made the demotion decision. Then there is the fact that the IAU definition stating a "dwarf planet" is not a planet at all makes no linguistic sense. If the definition is revised to make dwarf planets a subcategory of planets, this would be resolved. Also, Pluto is not just a rock sitting out there, and one can question whether the professor who regularly polls his 101 students does so after imposing his own biased view on them. The composition of asteroids is significantly different than the composition of planets, the latter of which characterizes Pluto and Eris.
Reply | Report Abuse | Link to this--
Edited by laurele at 04/15/2008 2:41 PM
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Edited by laurele at 04/29/2008 6:36 PM
Its not that I took Plutos demotion from planetary status personally. It makes me wonder, though, why I ever bothered to learn anything when I was young.
Reply | Report Abuse | Link to thisFirst, follow me back to brontosaurus. Remember him? Gigantic bronto, lumbering through prehistoric bulrushes at the edge of a Pleistocene lake, a dim-witted but powerful plant-eater. Fred Flintstone slid down his back in the opening credits every week. I loved that big, friendly dinosaur.
Turned out, Im the fossil. Hearing me mention the brontosaurus some years back, my eight-year old son wheeled about, fixed me with a disappointed gaze and announced professorially that, Dad, there is no such thing as a brontosaurus. Othniel Charles Marsh, who invented the name, mixed up the bones of two different dinosaurs he had dug up. The real name is apatosaurus. Since when, I asked. Since, like, 1975, he repliedcorrectly, it turns out. Why didnt I get the memo?
Paleontology isnt the only field where my knowledge has browned and died. Hawaii, my second son explained, was pretty much hijacked into statehood by American pineapple plantation owners, with a little help from a shipload of United States Marines. Queen Liliuokalani was under house arrest when she wrote Aloha Oe. Didnt you learn this in school? No, I did not. When I was a schoolboy, we were taught that the Queen and her subjects loved democracy and freedom and admired the United States so much that they requested admittance to the union, a wish graciously granted by President Grover Cleveland and the Congress. Seriously, that was in our textbooks.
I sympathize deeply with Alices Red Queen who despaired that It takes all the running you can do, to keep in the same place. My kids never tire of spinning me on the mental hamster wheel. So now I learn that Hernán Cortés and his small band of conquistadors did notcontrary to all Id been told beforeconquer Mexico with ease because the Aztecs were awed into submission by the sight of dazzlingly white men astride horses, acknowledging the invaders as gods. Instead, by the time the Spanish arrived in Montezumas capital, smallpox and other novel diseases carried into the New World by the Europeans had already decimated the population, rendering it unable to resist. Socrates instructs that there is no more important undertaking than the pursuit of truth. But honestly, is anybody better off knowing that Montezuma likely spent his last days doubled-over with the dysentery with which his name has since become associated?
And then Pluto. Pity Clyde Tombaugh, all those freezing cold nights in the Arizona desert, peeping up through a giant telescope, scanning for a tiny speck, the mysterious ninth planet that astronomers suspected ought to be out there. For what? Now, its just one of the ragtag mob of dwarf planets, tumbling erratically around the nether reaches of the slimmed-down solar system. When Tombaugh announced his discovery, in February, 1930, it was a rare bit of good news at the outset of the Great Depression. Plutos reduced circumstances today can have brought joy only to my cruel, overeducated children. Guess what, Dad, they asked at supper, triumph gleaming in their eyes. I suppose My Very Educated Mother wont Just Serve Us Nine Pizzas anymore. The boys tell me its just plain Noodles on the menu now. But with tiny Mercury and wobbly Neptune perhaps next in the reclassifying crosshairs of the International Astronomical Union, Im not sure I have the heart to commit another short-timer fact to long-term memory.