Galaxy clusters are thought to be the largest structures in the universe. Collisions between them may produce more energy than any events since the Big Bang, say researchers involved in the work. The research, which was first discussed last year, was presented Tuesday, Feb. 6 at a workshop on galaxy clusters in Sydney. Space is big. Until now there has been only weak evidence that clusters might collide.
Clusters are big groups of galaxies, huddled and held together by gravity.
Abell 3667 appears to have run into a slightly smaller galaxy cluster. As viewed from Earth, the distance between them is about twice the diameter of the Moon. But the readings are very faint. Afterwards you see only ripples and bits of wreckage, but that's enough to show that there's been a collision. The collisions might explain the origin of ultrahigh-energy cosmic rays, which remain a mystery.