Ongoing collision between at least three galaxy clusters

Astronomers have captured a spectacular ongoing collision between at least three galaxy clusters, combining NASA’s Chandra Observatory, ESA’s XMM-Newton Observatory, and three radio telescopes.

Collisions and mergers of this kind are the main way that galaxy clusters can grow into the gigantic cosmic edifices seen today. They also act as the largest particle accelerators in the universe, according to NASA.

The giant galaxy cluster forming from this collision is Abell 2256, located 780 million light-years from Earth. This composite image of Abell 2256 combines X-rays from Chandra and XMM in blue with radio data collected by the Giant Metrewave Radio Telescope (GMRT), the Low Frequency Array (LOFAR), and the Karl G. Jansky Very Large Array (VLA). all in red, plus optical and infrared data from Pan-STARRs in white and pale yellow.

Astronomers studying this object are trying to find out what gave rise to this unusual-looking structure. Each telescope tells a different part of the story. Galaxy clusters are some of the largest objects in the universe, containing hundreds or even thousands of individual galaxies. In addition, they contain huge reservoirs of superheated gas, with temperatures of several million degrees Fahrenheit. Only X-ray telescopes like Chandra and XMM can see this hot gas.

The radio emission from this system comes from an even more complex set of sources. The first is the galaxies themselves, in which the radio signal is generated by particles shooting out in jets from supermassive black holes at their centers. These jets shoot out into space in straight, narrow lines (the ones labeled “C” and “I” in the annotated image, using the astronomer’s naming system) or slow down as the jets interact with the gas with the that collide, creating complex shapes and filaments (“A”, “B” and “F”). Source F contains three sources, all created by a black hole in a galaxy aligned with the leftmost source of this trio.

The radio waves also come from huge filamentary structures (labeled “relic”), most located to the north of the radio-emitting galaxies, likely generated when the collision created shock waves and accelerated particles in the gas along more than two million light-years.

Finally, there is a “halo” of radio emission located near the center of the collision. Since this halo overlaps with X-ray emission and is dimmer than the filamentary structure and galaxies, another radio image has been produced to highlight the faint radio emission.