This one galaxy cluster is representative of over 80 clusters that were used to track the effects of dark energy on these massive objects over time. First shown in optical light, this galaxy cluster, Abell 85, is then seen in X-ray light from NASA's Chandra X-ray Observatory. Most of the matter in galaxy clusters is in the form of very hot gas, which emits copious amounts of X-rays. By studying clusters across large distances, astronomers have determined that dark energy has stifled their growth.
Credits: X-ray (NASA/CXC/SAO/A.Vikhlinin et al.); Optical (SDSS)