X-ray & Optical Images of Abell 1835, MS1455.0+2232, RXJ 1347.5-1145, and ZWCL 3146
These four galaxy clusters were part of a large survey of over 300 clusters used to investigate dark energy, the mysterious energy that is currently driving the accelerating expansion of the Universe. These images show X-rays from Chandra and optical light from Hubble and Sloan Digital Sky Survey. Researchers used a novel technique that takes advantage of the observation that the outer reaches of galaxy clusters, the largest structures in the universe held together by gravity, show similarity in their X-ray emission profiles and sizes.
(Credit: X-ray: NASA/CXC/Univ. of Alabama/A. Morandi et al; Optical: SDSS, NASA/STScI)