The first three heavenly bodies have ancient Japanese names:
Sun = Taiyou
Moon = Tsuki
Earth = Chikyuu
The next five planets have names based on the Chinese names, which are in turn based on the “Five Elements” of Chinese alchemy:
Mercury = Suisei – the water planet
Venus = Kinsei - the metal planet
Mars = Kasei - the fire planet
Jupiter = Mokusei - the wood planet
Saturn = Dosei - the earth planet
The final three planets have names that are direct translations of their meanings in Latin, because they were discovered after Japan’s renewed contact with the West:
Uranus = Tennousei - the heavenly king’s planet
Neptune = Kaiousei - the ocean planet
Pluto = Meiousei - the dark planet
These last three may have better translations. Those are mine, based on my limited understanding of the kanji.