Description: 在一年的时间里，当地球和地球上的所有天文观测者绕太阳运行时，这些观测者的视角会发生变化。与夜空中最遥远的天体作对比，这种视角变化导致了夜空中较近天体的视位置发生改变。这使得这些天体在一年的时间里在夜空中看起来移动在微小的椭圆轨迹上，这种效应被称为周年视差。视运动椭圆的主轴以角度表示，相当于天体（年）视差角的两倍。视差角相当于观测者位置变化一个天文单位（AU），即平均地日距离，或相隔半年的天文观测之间的地球位移的一半。距离单位”parsec“是”秒差距“的缩写，其定义是，对于距离地球1秒差距的恒星，年视差角相当于1角秒。

Related Terms:

• 视差

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

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