Due to this finding, astronomers' views of how clusters and individual galaxies evolve have changed. Space is big. Until now there has been only weak evidence that clusters might collide. The research was discussed at a workshop on galaxy clusters at the Australia Telescope National Facility headquarters in Sydney on Tuesday, Feb. 6.
Clusters are large groups of galaxies held together by gravity.
Abell 3667 appears to be a large cluster that has run into a slightly smaller one. The reason for this belief is a pair of arcs of radio emission that straddle the cluster 12 million light-years apart. Afterwards you see only ripples and bits of wreckage, but that's enough to show that there's been a collision. These types of radio arcs are extremely rare. The first ones found were thought to be ghostly remains of dead, dissipated galaxies and were dubbed 'relics', Ms Johnson-Hollitt explains.