A relatively large celestial body that orbits a star (e.g., Earth or Jupiter in the solar system).
望遠鏡で土星の輪やその周りの惑星を観察した。
I observed Saturn's rings and the planets around it with a telescope.
この系には多くの惑星が存在すると考えられている。
It is believed that many planets exist in this system.
太陽系の惑星は内側から水星、金星、地球、火星と続く。
The planets of the solar system, from the inside outward, are Mercury, Venus, Earth, Mars, and so on.
Figuratively, a surprise contender or someone who unexpectedly gains prominence (a 'dark horse').
今大会の若手選手はまさにダークホース、まさに惑星のようだ。
The young player in this tournament is truly a dark horse—like a surprise planet.
小さな会社が新製品で業界の惑星になった。
A small company became an industry dark horse thanks to its new product.