Credit: NASA, ESA, CXC, C. Ma, H. Ebelin

This composite image shows the massive galaxy cluster MACS J0717.5+3745 (MACS J0717, for short), where four separate galaxy clusters have been involved in a collision - the first time such a phenomenon has been documented. Hot gas in X-rays from NASA's Chandra X-ray Observatory have been combined with optical data from NASA's Hubble Space Telescope. The coolest gas is reddish purple, the hottest gas is blue, and the temperatures in between are purple. The repeated collisions in MACS J0717 are caused by a 13-million-light-year-long stream of galaxies, gas, and dark matter - known as a filament - pouring into a region already full of matter. MACS J0717 is located about 5.4 billion light-years from Earth. It is one of the most complex galaxy clusters ever seen.

Provider: Space Telescope Science Institute

Image Source: https://hubblesite.org/contents/news-releases/2009/news-2009-17

Curator: STScI, Baltimore, MD, USA

Image Use Policy: http://hubblesite.org/copyright/