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Glossary term: 恆星時

Description: 恆星時根據地球相對於夜空中遙遠恆星的自轉來計算時間。在夜晚,我們可以看到夜空中的恆星圍繞著我們旋轉。如果我們選擇一顆恆星,並記錄下它在天空中到達最高位置的時間,那麼整整一個恆星日之後,即用我們的時鐘測量的 23 小時 56 分 4.1 秒之後,這顆恆星將再次到達最高位置。

這與太陽日有著微妙的區別,太陽日是指連續兩天當地正午(太陽到達天空最高點的時間)之間的時間。由於地球還在繞太陽公轉,對於地球上的觀測者來說,一年中太陽在天空中的位置會發生額外的變化。在地球相對於遙遠恆星自轉一圈的時間裡,太陽已經移動了,地球需要再自轉一圈才能趕上。這就是太陽日比恆星日長一點的原因。

恆星日對天文學家來說很重要,因為它告訴他們在白天或夜晚的某個時刻,天空的哪些部分在頭頂上,從而可以觀測到哪些天體。在標準天文坐標系--赤道坐標系中,地球上任何地方(不包括兩極)的恆星時都是同一個角度,即天空正上方一點的赤經(該坐標系中用於指定天空中位置的坐標之一)。實際上,當今的天文學家在觀測時使用的是高度精確的原子鐘測量的時間,然後使用計算機計算哪個時鐘時間對應哪個恆星時。

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

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