A multicolor mosaic image of the massive galaxy cluster, Abell 370, located in the constellation Cetus – named for a sea monster in Greek mythology. Galaxy clusters are the largest structures in the universe bound by gravity, and consist of thousands of galaxies and large amounts of dark matter. Abell 370 formed when two less massive galaxy clusters merged together billions of years ago. It is more than 6.5 billion light-years away from Earth. The mosaic is approximately 4.5 million light-years across and has been constructed from deep optical imaging in the Legacy Surveys’ eighth data release. (Image: John Moustakas/Siena College; Legacy Surveys team)