They go out and point a telescope at the sky, take a picture, identify what are stars and throw them away, look at the galaxies, estimate how far away they are, and plot them up.
他们出去拿望远镜对准天空，拍一张图片 找出里面都有什么星星然后扔掉，然后再观察星系 估计他们离我们有多远，然后把它们分区画好