距离太阳系最近的恒星是半人马星座 a 星,它距地球约 4.5 光年.若宇宙飞船相对于地球的速度为 v =0. 866 c ( c 表示真空中的光速 ) ,要自地球飞到半人马星座 a 星,按 飞船上的时钟 计算 , 需要 _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 年 .
A.
2.6
B.
5.2
C.
7.8
D.
10.4
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