双節棍[nunchaku] nunchaku (two linked fighting sticks)
一双[issou] pair (esp. of folding screens)
一卵性双生児[ichiranseisouseiji] identical twins
双紙[soushi] written work (esp. a bound text, as opposed to a scroll)
自己双対[jikosoutsui] self dual

双刃[moroha] double-edged
双暗車[souansha] twin propellers
双殻類[soukakurui] bivalves
双眼[sougan] both eyes

異星人[iseijin] alien (from another planet)
一つ星[hitotsuboshi] evening star
１等星[ittousei] first-magnitude star
衛星[eisei] satellite
衛星地球局[eiseichikyuukyoku] (satellite) earth station

衛星放送[eiseihousou] satellite broadcasting
火星[kasei] Mars (planet)
火星人[kaseijin] Martian
海王星[kaiousei] Neptune (planet)
巨星[kyosei] giant star