This is why I said "spheroidal", not "spherical". Even the Earth is oblate.Michael Kilderry wrote:I think the best way to determine if something is a planet or not might be whether it is spherical in shape or not, but even this has problems.
What if we discover an object 1km in diameter that is very spherical in shape, just by chance? And where do we draw the line between spherical and irregularly shaped objects? What about the oblate Jupiter?
As for such a world to be in that condition, it would probably be better to see if the candidate is of sufficient mass to condensate spheroidally, rather than being shaped by happenstance. Additionally, to achieve this condition, a layered density structure- ie: a core- will have formed as part of its mass condensation.
Thus the question is, not about its size, but whether it has sufficient mass to have formed a spheroid entirely on its own. This is the only practical way to determine planethood.
A 1km object is just not going to have the mass to be spheroidal unless it's made of neutrons or quarks!
I'm beginning to think the universe wasn't made for planets to be classified depending on characteristics, there's always something that breaks the rule.
The Universe could care less about defining things by nice, rounded-off artificial measurements, such as 2000km diametres, because the Universe doesn't understand such arbitrary and artificial measurements. Physics doesn't work that way.
d.m.f.