Merging galaxy clusters at first contact
Multi-wavelength view of galaxy clusters 1E2216 and 1E2215, which appear to come into first contact ahead of merging.
The two hot, X-ray emitting gas halos associated with each cluster, with temperatures in excess of 50 million degrees Celsius, appear to be connected by a bridge of even hotter gas, reaching up to 100 million degrees Celsius.
Additional observations revealed that this gas bridge is shock-heated, with shock fronts propagating on either side from the inside out, along the equatorial plane of the merger. The presence of such a shock indicates that the two clusters are in the pre-merger phase, coming into contact for the very first time – something that has never been observed before.
The two galaxy clusters are located over one billion light years away from the Earth and have been drawn towards each other by gravity for billions of years. While the pre-merger phase lasts for a relatively short period of time – around 100 million years – the entire merging process takes billions of years to complete.
The image combines optical observations from the Sloan Digital Sky Survey (in the g, r, i filters) with X-ray data collected between 0.5 and 8.0 keV by NASA's Chandra space observatory (blue) and radio data at 325 MHz from the Giant Metrewave Radio Telescope, located in India (red).
The image spans about 10 arcminutes across.