We didn't see a surplus toward the nearby Virgo galaxy cluster, for example, so they'd have to be coming from even more distant galaxies, clear across the Universe!

例如，我们没有看到靠近处女座星系团有任何余光，所以它们一定来自更遥远的星系，完全横跨了宇宙！

Like star clusters, galaxies in galaxy clusters are bound to the cluster by their own mutual gravity, and move through the cluster on long orbits that can take billions of years to complete.

就像星团一样，星系团中的星系通过自身的相互引力与星系团结合在一起，并沿着可能需要数十亿年才能完成的长轨道在星系团中移动。