Another measure comes from counting the number of clusters of galaxies in the universe to measure the volume of space and the rate at which that volume is increasing. (britannica.com)
The highest peaks in the maps correspond the foreground massive clusters of galaxies that lie 5 billion light - years away. (sciencedaily.com)
Some of the most dramatic evidence of dark matter shows up in images of large clusters of galaxies. (discovermagazine.com)