Is there a thin line between jealousy and admiration?

I am sure I am not the first person to think of this. Granted that jealousy is an ugly emotion, but it seems to me that at least in some cases the only distinction between jealousy and admiration is that the admired person is perceived to be completely out of one’s league whereas in the case of jealousy the perception is that the person is on one’s own level. Comments?