其中一颗三十天沿轨道运行一周，而另一颗所需时间恰好是它的运行周期的两倍。

One takes 30 days to complete an orbit, the other exactly twice as long.

youdao

其中一颗三十天沿轨道运行一周，而另一颗所需时间恰好是它的运行周期的两倍。

One takes 30 days to complete an orbit, the other exactly twice as long.

youdao