Description: 海王星是第八大行星，也是距離太陽最遠的行星。和它的鄰居天王星一樣，海王星也是一顆冰巨行星。海王星的半徑略小於 2.5 萬公里，是地球半徑的四倍。海王星有一個堅固的岩石核心，周圍有一層高壓水、甲烷和氨。在太陽系外的早期，這些化學物質被凍結並吸附在年輕的海王星上，因此被稱為 "冰巨行星"。海王星的外部大氣層是一層厚厚的、蓬鬆的氫和氦。

它與太陽的典型距離約為 45 億千米，約為 30 個天文單位（地球-太陽距離）。海王星至少有 14 顆衛星和一個微弱的行星環。作為最外層的主行星，海王星的引力在塑造柯伊伯帶中較小天體的軌道方面起著關鍵作用。

肉眼看不到海王星。最初發現海王星是因為它的引力對天王星軌道的影響。數學家約翰-庫奇-亞當斯（John Couch Adams）和烏爾班-勒威耶（Urbain Le Verrier）都在 19 世紀 40 年代初預測了海王星的存在和位置。根據勒威耶的計算，約翰-戈特弗裡德-加勒於 1846 年首次確認了海王星。海王星以羅馬海神的名字命名。

Related Terms:

• 天文單位
• 巨行星
• 冰雪巨人
• 柯伊伯帶
• 外行星
• 太陽系
• 天王星

Term and definition status: The original definition of this term in English have been approved by a research astronomer and a teacher
The translation of this term and its definition is still awaiting approval

This is an automated transliteration of the simplified Chinese translation of this term

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