Other rich clusters show the same segregation of the spirals from the ellipticals as the Coma Cluster. Ellipticals gather together in the center of clusters while spirals prefer to stay close to the periphery. The Coma cluster is a rich galaxy cluster with thousands of galaxies. The Hercules cluster is a poor cluster with less than a hundred galaxies. The clustering phenomenon does not stop with galaxies.
Galaxy clusters attract each other to produce superclusters of tens to hundreds of clusters.
The discovery of these huge structures was made recently from years of taking doppler shifts of thousands of galaxies. The doppler shifts of the galaxies were converted to distances using the Hubble Law . The voids are typically 150 million light years across. Two pioneers in the mapping of the structure of the universe are Margaret Geller and John Huchra. They and their students have taken thousands of spectra of galaxies along thin pie-shaped slices of the sky.