Pluto's status could shift yet again, as astronomers are mounting a grassroots campaign to readdress the definition of a planet.
More than 300 researchers have signed a statement denouncing the recently adopted definition that relegates Pluto to "dwarf planet" status, and some are planning a conference in 2007 to hash out an alternative definition.
Last week, scientists at a meeting of the International Astronomical Union (IAU) in Prague, Czech Republic, voted to approve a new planet definition that recognises only eight planets.
But many astronomers find fault with the new definition's criteria – which state a planet must have cleared out the neighbourhood around its orbit. There have also been complaints about the small number of scientists allowed to vote on the issue (see New planet definition sparks furore).
Now, disgruntled astronomers are planning a conference to fix what they see as a flawed definition. One of the conference organisers is Alan Stern, who heads NASA's New Horizons mission to Pluto.
He says there will be about 20 planetary scientists organising the meeting, which could be attended by 1000 astronomers. It would probably occur in mid-2007, although there could be smaller working meetings ahead of the conference itself.
Stern says the definition is important because categorising things is a key part of science. "As scientists, part of our job is to reduce the mass of facts to a smaller number of concepts," he told New Scientist.
The IAU is responsible for naming solar system objects like planets and their moons, so its definition of a planet is the official one.
It is possible that the definition could be revised at the next IAU general assembly meeting in 2009, but in the meantime teachers and textbook writers are wondering how to explain the concept and which objects to include in descriptions of the solar system.
"Teachers are writing me saying, 'We don't know how to teach this,'" Stern says. "We've got to help them out of this jam that the IAU has put them in."
Conference co-organiser Owen Gingerich of Harvard University in Cambridge, Massachusetts, US, says a definition other than the one decided by the IAU could win out in practice if more textbook authors choose to use it.
Gingerich chaired the IAU committee that recommended a definition that would have included 12 planets – a proposal that was rejected at last week's meeting.
"If the conference is broadly enough representative with the key players, then it may well be that it establishes a different nomenclature than what has been officially voted on by the IAU," he told New Scientist. "It might achieve a more satisfactory consensus."
The IAU so far does not have any plans to revisit the definition before the 2009 meeting, says incoming IAU vice president Martha Haynes of Cornell University in Ithaca, New York, US.
"I don't think there's been any discussion of that in any official sense," she says, noting that the issue could also potentially be discussed at an upcoming meeting of the American Astronomical Society's Division of Planetary Sciences (DPS) in October 2006.
But she says the IAU may change its voting policy to allow more members to have their say in official decisions, including the contentious issue of what constitutes a planet.
Only scientists who were physically present in the IAU meeting room in Prague last Thursday were allowed to vote, a restriction that some astronomers say is unfair. She says allowing votes by email might be considered for future IAU decisions.
"I'm sure there will be discussion of whether we could do things better," Haynes told New Scientist. “I'm a strong supporter of processes which are transparent and inclusive, and I am sure the executive committee will give the IAU process a careful review.”
Meanwhile, the DPS issued a statement on Thursday saying it recognises the IAU's authority to decide on a planet definition. But it added that "future refinements of this definition will almost certainly be desired. Ultimately, the definition of a planet will come through common usage and scientific utility."
By Alvin
Wed Aug 06 16:50:24 BST 2008
To me a planet should be able to substain, an atmosphere, no matter what its made of as long as its global..... And stable.All comments should respect the New Scientist House Rules. If you think a particular comment breaks these rules then please use the "Report" link in that comment to report it to us.
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18:00 07 October 2008
17:56 07 October 2008
