Description: 視差是由於觀察者視點的變化，導致天體在天空中位置的表觀變化。天空中的位置變化，以角度表示，是相對於我們所知道的最遠的物體來確定的——過去是使用遙遠的恆星；是被稱為類星體的極其遙遠的物體，它們確定了所謂的國際天球參考框架。視位置變化的角度與天體離我們的距離成反比，因此視差測量是確定鄰域天體距離的有力工具（"視差法"）。對於太陽系天體，從地球上不同位置同時進行觀測可以得到有效的視差值。對於恆星來說，視差角是觀測者位置與視線成直角移動一個天文單位（地球-太陽平均距離）時的偏移值。觀測者的位置移動量可以通過相隔幾個月的觀測來實現，在這幾個月之間，地球沿著圍繞太陽的軌道移動。根據定義，在這種條件下視差角為 1 弧秒的天體與地球的距離為 1 秒差距（3.26 光年）。在一年中，恆星在天空中的視位置會劃出一個橢圓，其半主軸就是視差角。迄今為止最精確的恆星視差是由歐空局的蓋亞任務提供的，蓋亞任務是專門為這項任務設計的太空望遠鏡。

Related Terms:

• 週年視差

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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