But my rotation period is unknown, now isn't that weird?

但是我的自然周期仍然未知，有点奇怪吧？

And by matching the rotation periods on the map with stellar signposts in the sky, aliens could find their way to Earth relatively easily.

通过将地图上的自转周期与天空中的指路星体一比照，外星人就可以相对容易地找到通往地球的路。