Watching Astronauts train: Fun!!! Bigest exkplosion in history from Ophiuchus galaxy cluster about 390 million light-years from Earth. Galaxy clusters are the largest structures in the universe held together by gravity, containing thousands of individual galaxies, dark matter, and hot gas. The explosion blew out a hole in the wall of the cluster. This explosion was 5 x bigger than the previous record holder. The biggest explosion of course, was the Big Bang. The previous record holder, MS 0735+74, and hundreds and thousands of times greater than typical clusters.