I'm writing a story where there's a federation of minor planets that uses Esperanto as its official language. I'm trying to call them something like "the federation of minor planets", because I'm not creative, and came up with "Federacio de la Planedetoj". However, I'm looking for something that means "composed of", and "de" doesn't seem to mean that. I guess I could make something up about how they specifically chose "de" to emphasize that they're controlled by the minor planets, but I'd still prefer to find a preposition that means the right thing.
TL;DR: What's the word for "composed of"?
Incidentally, if anyone wants to provide a better translation for any other part of the phrase, please do.