This word order is confusing to me. Why not z jakiej planety jestes? Or jestes z jakiej planety? Why split jakiej and planety. Is this more natural in polish?
the "from which" is like one of the few actual rules we have- you always have
preposition+adjectives/other describing words+noun/pronoun.
I think "From which one are you of the planets" would be a better literal translation.
Can this be asked in a sarcastic way to poke fun at a friend, as it is in English?
Unless you actually meant to say that you are with someone called Joviuś ;)
You're right. And both forms are correct in proper context. That said, for some reason when asking about places, e.g. From which city, country, planet are you? We use "Jaki" not który. I've never really thought about it, and man, it's weird. It seems to me that "który" is more about differentation from group of the same objects.
Well, we generally try to keep to jaki = what (what kind of) and który = which. The English sentence uses "what", the Polish one uses "jakiej". And "której" would indeed, as Kwarkje wrote, sounds as if there was a closed group to choose from.
They really do. Polish have way too many exceptions in my opinion, being naturally evolved and quite old much of it is explained by history of it. Nonetheless, it still irks each new genertion of learners. Last time when it was reformed a little was a hundred years ago.
from which planet you are ? was refused. I suppose this is not correct English ?
Yes, that's not a correct word order of an English question. It should be "From which planet are you?" to be correct, although I believe that's not exactly a common order nowadays.