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, 02:02 PM
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Senior Member Group: Members Posts: 1018 Joined: 29-November 05 From: Seattle, WA, USA Member No.: 590 |
It does seem that it would have been useful to create a more general term (e.g. planetoid) to cover any non-fusing body rounded by its own gravity (absent effects of rotation or tides) but ignoring its orbital dynamics. Eath, Luna, Ceres, Titan, etc. would all be planetoids. Everything smaller could be an asteroid (or maybe a new name), while everything larger would be a star. Only a truly transforming cataclysm could transform one into another.
A multiple planetoid would just be any long-term stable, gravitationally bound set of planetoids. (Likewise you could have a multiple asteroid I guess.) The planet vs. moon distinction still comes down to whether one member of the system sufficiently dominates the rest. I suppose the barycenter definition is as good as any for this purpose, although it bothers me that it depends on the density of the planet(oid). This also suggests that we might usefully make a distinction between a "moon," which would have to be a planetoid, and a "moonlet" (is there a better name) which is just an asteroid that's gravitationally bound to a planetoid. |
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