Astronomers also use another unit called a parsec.

天文学家用另一种单位——秒差。

They use a distance called the parsec (a contraction of parallax and second), based on a universal measure called the stellar parallax and equivalent to 3.26 light-years.

他们用的离单位是“秒差”一种普遍用的、名叫恒视差的量度方法，相当3.26光年。