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This composite image from NASA's Chandra X-ray Observatory and Hubble Space Telescope shows the massive galaxy cluster MACS J0717 where four separate galaxy clusters have been involved in a collision — the first time such a phenomenon has been documented.
MACS J0717 is located about 5.4 billion light-years from Earth. It is one of the most complex galaxy clusters ever seen.
Image Credit: NASA, ESA, CXC.