Pluto, still perched on its planetary precipice
Despite the draft definition released by the International Astronomical Union (IAU) on Wednesday that would have qualified Pluto's status as a planet and added three others, New Scientist reports that a competing proposal may yet see a return to the eight so-called 'classical' planets.
The IAU Planet Definition Committee had said anything that is not a star but that is round and independently orbits the Sun should be considered a planet, while any planet farther than Neptune should also be called a pluton. This would mean that the four rocky planets (Mercury, Venus, Earth, Mars) and four gas giants (Jupiter, Saturn, Uranus, Neptune) would be planets, as would Ceres (currently classified as an asteroid), Pluto, Charon and 2003 UB313 ('Xena'). The latter three would also be plutons, and an unknown number of other objects could also be recognised as planets and as plutons in future, depending on how strictly 'roundness' is defined.
On Friday, a group led by Julio Fernández from Montevideo's University of the Republic proposed that an additional criteria should be stipulated - that a planet should be 'by far the largest body in its local population'. If this was approved, the number of planets would return to eight and objects such as Pluto would be dwarf planets. It would be unlikely that any further unqualified planets would be added, since this would involve the discovery of a massive planet farther than Neptune.
The IAU votes on Thursday, but in the meantime a straw poll of astronomers at John Hopkins University in Baltimore, which was released the same day as the second proposal, threw up a range of interestingly conflicting opinions.
Of course this is more a matter of language than science, but I reckon we should return to eight 'proper' planets - much simpler (the textbooks would have to be rewritten either way!).
The IAU Planet Definition Committee had said anything that is not a star but that is round and independently orbits the Sun should be considered a planet, while any planet farther than Neptune should also be called a pluton. This would mean that the four rocky planets (Mercury, Venus, Earth, Mars) and four gas giants (Jupiter, Saturn, Uranus, Neptune) would be planets, as would Ceres (currently classified as an asteroid), Pluto, Charon and 2003 UB313 ('Xena'). The latter three would also be plutons, and an unknown number of other objects could also be recognised as planets and as plutons in future, depending on how strictly 'roundness' is defined.
On Friday, a group led by Julio Fernández from Montevideo's University of the Republic proposed that an additional criteria should be stipulated - that a planet should be 'by far the largest body in its local population'. If this was approved, the number of planets would return to eight and objects such as Pluto would be dwarf planets. It would be unlikely that any further unqualified planets would be added, since this would involve the discovery of a massive planet farther than Neptune.
The IAU votes on Thursday, but in the meantime a straw poll of astronomers at John Hopkins University in Baltimore, which was released the same day as the second proposal, threw up a range of interestingly conflicting opinions.
Of course this is more a matter of language than science, but I reckon we should return to eight 'proper' planets - much simpler (the textbooks would have to be rewritten either way!).
Labels: science
posted by Kuvera at
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