Glossary term: 行星環
Description: 太陽系中的四顆巨行星（木星、土星、天王星和海王星）都被無數小冰塊或岩石所環繞，這些微小物質的尺寸從微米到數米不等，形成了巨大的行星環結構。目前，我們還無法確定系外行星是否有類似的環系統。最壯觀的行星環是圍繞土星的復雜環系統，由多個環組成，並被環縫分隔開。其中一些結構是由與土星較大的衛星相互作用而形成的，而環內軌道運行的小衛星則清理出了環縫。關於這些行星環的形成有多種假說，大多數認為是由於衛星在土星引力作用下被撕裂或剝離而形成。據估計，土星的行星環將在幾億年內逐漸消失——從天文學的標準來看，這並不是很長的時間。木星、天王星和海王星的環系統相對不那麼明顯。
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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
This is an automated transliteration of the simplified Chinese translation of this term
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土星
Credit: 美國國家航空航天局、歐空局、A. Simon（戈達德太空飛行中心）和 M.H. Wong（加州大學伯克利分校） credit link
License: CC-BY-4.0 Creative Commons 姓名標示 4.0 國際 (CC BY 4.0) icons
天王星與星環
Credit: 美國國家航空航天局、歐洲航天局和 M. Showalter（SETI 研究所） credit link
License: PD Public Domain icons
