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Originally Posted by [1ponders]
Great discussion guys. What are the feelings about using a naming system based on size? Planet (minimum size = mars), planetoid (minimum size = 500km) and planetesimal (down to about 150 km), smaller than that asteroid. Comets stay as they are.
Or alternatively, based on distance from the sun and size, major planets = mercury out to pluto, minor planets out past pluto
Just some thoughts
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All reasonable approaches Paul, but as I've outlined below this sort of classification by drawing boundaries along continuum variables such as distance or diameter is entirely arbitrary - meaning you could easily draw boundaries at different points and be equally justified, so it will be difficult to get agreement. If we are to classify we should seek qualitative rather than quantitative variables that distinguish bodies with fundamentally different evolutionary histories - easier said than done. A good example is the method of distinguishing stars from non-stars based on internal fission of hydrogen into helium. This provides a convenient qualitative point of difference rather than simply saying stars with >0.05 solar masses are stars. It's also scientifically meaningful in that the history and future of the "body" on one side on this divide will experience a very different history and future to one on the other side.
cheers,