Japanese is a language rich in vocabulary, including words related to astronomy and the planets. Learning these terms not only broadens your lexicon but can also enhance your understanding of the culture, as many Japanese words have historical and mythological significance. Below you’ll find a selection of Japanese words for planets and astronomical terms accompanied by their definitions and example sentences.

惑星 (わくせい; wakusei)
This is the general term for “planet” in Japanese. It combines the characters for “bewilder” or “lead astray” (惑) and “star” (星).

太陽系には８つの惑星があります。
(There are eight planets in the solar system.)

太陽 (たいよう; taiyō)
“Sun”; from the characters meaning “thick” or “big” (太) and “sun” or “positive” (陽).

太陽は今日も明るく輝いています。
(The sun is shining brightly today as well.)

月 (つき; tsuki)
“Moon”; a straightforward term with no kanji combination, representing the satellite we see orbiting our planet.

今夜、月がとても美しいです。
(Tonight, the moon is very beautiful.)

水星 (すいせい; suisei)
“Mercury”; the planet closest to the sun, combining the characters for “water” (水) and “star” (星).

水星は小さくて、太陽に近いから、なかなか見ることができません。
(Mercury is small and close to the sun, so it’s hard to see.)

金星 (きんせい; kinsei)
“Venus”; combining “metal” or “gold” (金) and “star” (星), often associated with beauty and brightness.

金星は明け方と夕方によく見えます。
(Venus is often visible at dawn and dusk.)

地球 (ちきゅう; chikyū)
“Earth”; from the characters for “earth” or “ground” (地) and “sphere” (球).

私たちは地球という惑星に住んでいます。
(We live on a planet called Earth.)

火星 (かせい; kasei)
“Mars”; consists of “fire” (火) and “star” (星), possibly referring to its reddish appearance.

火星には生命が存在すると考えられています。
(It is thought that there might be life on Mars.)

木星 (もくせい; mokusei)
“Jupiter”; joining the characters for “tree” or “wood” (木) and “star” (星).

木星は太陽系で一番大きな惑星です。
(Jupiter is the largest planet in the solar system.)

土星 (どせい; dosei)
“Saturn”; made up of “soil” or “earth” (土) and “star” (星), known for its distinctive rings.

土星の輪は望遠鏡で見えることがあります。
(The rings of Saturn can sometimes be seen with a telescope.)

天王星 (てんのうせい; tennōsei)
“Uranus”; the characters translate to “heavenly king star” (天王星).

天王星は普通の望遠鏡では見えないことが多いです。
(Uranus is often not visible with a normal telescope.)

海王星 (かいおうせい; kaiōsei)
“Neptune”; translates to “sea king star” (海王星).

海王星は非常に遠いので、詳細はよくわかっていません。
(Neptune is very far away, so not much is known about it in detail.)

星座 (せいざ; seiza)
“Constellation”; combining “star” (星) and “seat” or “location” (座).

空にはたくさんの星座があります。
(There are many constellations in the sky.)

天の川 (あまのがわ; Amanogawa)
“The Milky Way”; the characters translate to “heaven’s river” (天の川), reflecting the Milky Way’s appearance as a river of stars in the sky.

夏の夜空には天の川がきれいに見えます。
(The Milky Way is beautifully visible in the summer night sky.)

Whether you’re an aspiring astronomer or simply a language enthusiast, these Japanese words can help you discuss the cosmos with confidence and a better grasp of how astronomical objects are perceived in Japanese culture. As you continue to explore both the night sky and the Japanese language, keep an eye (or a telescope!) out for these celestial terms.