最終更新日：2025/11/21

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(astronomy) A hypothetical planet in the Solar system, beyond the currently known outermost planet. (The term was applied to Eris for a short while, when Pluto was still considered the ninth planet.)

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Planet X

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Planet X

固有名詞

廃用

(astronomy) A hypothetical planet in the Solar system, beyond the currently known outermost planet. (The term was applied to Eris for a short while, when Pluto was still considered the ninth planet.)

日本語の意味

天文学用語。太陽系の既知の最外縁惑星の外側に存在すると仮定される惑星。プルートがまだ第9惑星とされた時期、短期間エリスに適用されていた用語。

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Some astronomers continue to search for Planet X despite decades of debate over its existence.

Google翻訳 / DeepL翻訳

一部の天文学者は、その存在をめぐる何十年にもわたる議論にもかかわらず、太陽系で現在知られている最も外側の惑星の外側にある仮説上の惑星を探し続けている。

詳細

意味（1）

(astronomy) A hypothetical planet in the Solar system, beyond the currently known outermost planet. (The term was applied to Eris for a short while, when Pluto was still considered the ninth planet.)

意味（2）

(astronomy, obsolete) A theoretical planet responsible for reported gravitational perturbations of Neptune's orbit. (This was initially believed to be Pluto. The reported perturbations were an error.)

意味（3）

詳細

Planet X

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Planet X

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