Experts meet to decide Pluto fate, Finally we'll know what a 'planet' is... |
Experts meet to decide Pluto fate, Finally we'll know what a 'planet' is... |
Aug 14 2006, 06:06 AM
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Member Group: Members Posts: 295 Joined: 2-March 04 From: Central California Member No.: 45 |
-------------------- Eric P / MizarKey
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Aug 16 2006, 04:51 PM
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#2
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Junior Member Group: Members Posts: 78 Joined: 29-December 05 Member No.: 623 |
"A planet is a celestial body that (a) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape...."
The "roundness" criterion seems to me to be the start of a good definition. And if Pluto is a planet so is Ceres. However, the qualificaitions of "dwarf planet," "pluton," and planet-if-beyond-the barycenter seem extraneous. But there is a problem here. Keep in mind that we have no idea if Callisto is truly in hydrostatic equilibrium, so surely we have no idea about 2003 UB313. In reality the definition can't really be of "hydrostatic equilibrium" without defining an error bar. This seems pedantic but becomes a real issue: does Vesta count? Before its large impact, its shape was probably hydrostatic (cf. Thomas et al., Science 277, 1492 - 1495, 1997). Is Vesta penalized just for being whacked with an impact large compared to its radius? |
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