Recebido via net.
So, let's see:
(1) Ceres -- after 206 years as an "asteroid" -- is suddenly reclassified as a planet.
2) Several KBOs considerably larger than Ceres are nevertheless not planets, apparently because they're icy and thus not massive enough to have probably "rounded" themselves gravitationally.
3) The precise defintion of "rounded" is apparently left totally ambiguous. (Is Pallas round? Is Vesta -- which differs mildy but significantly in its axial widths? Is Iapetus round, since it's about 1500 km wide but its axial widths differ by about 50 km? What about Neptune's moon Proteus, which looks like a marshmallow? or 2003 EL61, which is cigar-shaped, as wide as Pluto along its long axis but only half as wide along its shorter ones?
4) Charon is suddenly a "planet" despite the fact that it orbits Pluto (which in itself is defensible given the definition of a "binary planet" as one whose barycenter is beyond the outer surface of either partner), has been called a "moon" for 28 years, and is only about 1000 km across.
So, let's see:
(1) Ceres -- after 206 years as an "asteroid" -- is suddenly reclassified as a planet.
2) Several KBOs considerably larger than Ceres are nevertheless not planets, apparently because they're icy and thus not massive enough to have probably "rounded" themselves gravitationally.
3) The precise defintion of "rounded" is apparently left totally ambiguous. (Is Pallas round? Is Vesta -- which differs mildy but significantly in its axial widths? Is Iapetus round, since it's about 1500 km wide but its axial widths differ by about 50 km? What about Neptune's moon Proteus, which looks like a marshmallow? or 2003 EL61, which is cigar-shaped, as wide as Pluto along its long axis but only half as wide along its shorter ones?
4) Charon is suddenly a "planet" despite the fact that it orbits Pluto (which in itself is defensible given the definition of a "binary planet" as one whose barycenter is beyond the outer surface of either partner), has been called a "moon" for 28 years, and is only about 1000 km across.
You want to know what the reaction of the general public will be to this baffling farrago? Take a look at Kevin Drum's reaction at http://www.washingtonmonthly.com/archives/individual/2006_08/009347.php - and Drum is a highly educated layman. Now consider what Jay Leno's reaction will be, along with that of millions of befuddled children AND their equally befuddled teachers. Astronomers have just shoved a pie in their own faces unequalled since the Hubble Mirror Affair. And it couled have been avoided if the defintion of "planet had instead just been set at some unavoidably) arbitrary but easty-to-remember figure -- such as a maximum-axial diameter of 200 km -- which allowed Pluto in but kept out legions of small and confusing riffraff (while also maintaining the binary-planet concept, for the day when we finally discover a binary KBO whose smallest member has a maximum diameter of over 2000 km).
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