Description: 冥王星是太陽系中的天體之一。它位於柯伊伯帶，在海王星軌道之外。它曾被稱為太陽系第九大行星，但在 2006 年被重新歸類為矮行星。它於 1930 年被克萊德-湯博發現。冥王星與太陽的平均距離為 60 億千米，半徑為 1185 千米（比地球的衛星還小）。冥王星上的一年相當於地球上的 247.9 年，一天相當於地球上的 6.4 天。

2015年，美國國家航空航天局的 "新視野 "號飛船成為第一個飛越冥王星的航天器，並首次提供了冥王星表面及其大氣層的詳細信息。冥王星表面非常寒冷，幾乎沒有氫可以以氣態形式存在。冥王星僅有的一點大氣主要是氮氣，表面有大片冰凍的氮氣平原。它的大氣層延伸到1600千米的距離。冥王星由岩石（70%）和冰（30%）組成。它有五顆已知的衛星：卡戎（Charon）、斯提克斯（Styx）、尼克斯（Nix）、刻耳柏洛斯（Kerberos）和海德拉（Hydra）。

Related Terms:

• 天體
• 矮行星
• 柯伊伯帶
• 海神
• 太陽系

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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