Description: 光年是一個長度單位，在天文學中有時用來表示極遠的天文距離，如恆星之間或星系之間的距離。它的定義是光在真空中傳播一年所行進的距離：9.46萬億千米，即9.5×10¹²千米。使用“光年”這個單位後，極遠的距離在數字上就變得更容易處理了：距離太陽最近的恆星有40萬億千米，更簡單地說就是4.25光年。天文學家還使用“光分”以及“光時”這兩個單位：光從太陽出發，到達地球大約需要8分鐘，到達海王星大約需要4小時。“光年”這個術語在天文學研究中實際上很少使用，因為天文學家更傾向於使用“秒差距”（約 3.26 光年）來衡量距離。

Related Terms:

• Parsec

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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