Clusters of Galaxies

Clusters of galaxies are the most massive gravitationally bound objects in the universe. OIR scientists study images and spectra of clusters to determine their masses, distribution, and the properties of the clusters and their member galaxies. The large velocities of cluster galaxies provided the first evidence of dark matter. Today, scientists continue to study clusters to understand how dark matter and galaxies are connected. Clusters are rare objects that have been formed recently; the abundance of clusters and their recent evolution therefore measure the amount of structure in the universe and its growth history.