Galaxy Clusters(def.): def. Galaxies can swarm together to form groups and clusters of galaxies held together by their mutual gravity. X-ray observations show that these enormous systems of galaxies are filled with colossal clouds of hot gas.

Galaxy clusters are the largest objects in the Universe held together by gravity. Chandra detects the superheated gas that fills the space between the hundreds and thousands of galaxies in these enormous clusters. Galaxy clusters are used to investigate mysteries of dark matter and dark energy. More >