Glossary term: 星云
Description: 星云是一种遥远的天体,具有云的外观。通常,星云由星际气体和尘埃组成。在历史上,星云一词指的是所有延展的、边缘模糊的天体,包括我们今天所认识的星系--像银河系这样的遥远恒星系统。如今,星云一词仅限于指代星际介质中的气体和尘埃云,即星系内恒星之间的气体和尘埃。星云被分为许多不同的种类:分子云相对较冷,颜色较暗,主要由分子氢组成;新的恒星就是在这样的云中形成的。巨型分子云可以包含多达数百万个太阳质量的氢气。年轻恒星频繁地喷射出狭窄的电离气体喷流;当这些喷流激发周围的气体时,就会形成一种叫做赫比-哈罗(Herbig–Haro)天体的星云。当大质量恒星形成后,它们的强烈辐射会使周围的气体发出特征性的红光;这种由炽热的电离氢气组成的星云被称为 HII 区(电离氢区)。其他类型的星云与恒星的死亡有关:低质量恒星的死亡会留下不断膨胀的气体外壳,这种星云(命名上有些令人困惑)被称为行星状星云。当大质量恒星以超新星的形式爆发时,喷出的气体会形成一种叫做超新星遗迹的星云。
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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
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License: CC-BY-4.0 Creative Commons 署名 4.0 国际 (CC BY 4.0) icons
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License: CC-BY-4.0 Creative Commons 署名 4.0 国际 (CC BY 4.0) icons
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License: CC-BY-4.0 Creative Commons 署名 4.0 国际 (CC BY 4.0) icons
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License: CC-BY-4.0 Creative Commons 署名 4.0 国际 (CC BY 4.0) icons
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License: CC-BY-4.0 Creative Commons 署名 4.0 国际 (CC BY 4.0) icons
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