Also known as Uranian planetoids, Class I: Ice Giants are massive,
frozen worlds that lurk on the outskirts of a star system. They are
also dramatically different from their gaseous brethren; while
Class J: Jovian planets are massive spheres of hydrogen and
helium, Class I worlds are typically composed of tenuous layers of
water, ammonia, and methane, surrounding a small core of ice and
iron. Many ice giants also have magnetic fields that are sharply
inclined to the axis of rotation.