This is a composite image of X-rays from Chandra and optical data from Hubble of the galaxy cluster ACT-CL J0102-4915, located about 7 billion light years from Earth. This cluster has been nicknamed "El Gordo" (or, "the fat one" in Spanish) because of its gigantic mass.
Scientists first announced the discovery of El Gordo with Chandra and ground-based optical telescopes in 2012. They determined that El Gordo is the most massive, the hottest, and gives off the most X-rays of any known galaxy cluster at its distance or beyond.
New data from the Hubble Space Telescope suggests El Gordo weighs as much as 3 million billion times the mass of our Sun. This is about 43 percent higher than the original estimate based on the X-ray data and dynamical studies.
-Megan Watzke, CXC