Pandora’s Cluster Has Extremely Violent History

An international collaboration of researchers says that one of the most interesting galaxy clusters in the known Universe is the result of a violent collision between four individual galaxy clusters. The merging process lasted for more than 350 million years.

In order to study the structure, which is called Abell 2744, experts used a variety of telescopes, both on the ground and in Earth's orbit. Some of the most important ones were the NASA Hubble Space Telescope and the Very Large Telescope.

The VLT is located at the Paranal Observatory, which the European Southern Observatory (ESO) operates atop Cerro Paranal, in the Atacama Desert in northern Chile. The instrument has four separate telescopes, which function via interferometry.

Using this impressive array of capabilities, researchers determined that the cluster they see today was in fact not formed steadily, or through simple mergers, but rather during a 4-way collisions that laster for hundreds of millions of years.

“We nicknamed it Pandora’s Cluster because so many different and strange phenomena were unleashed by the collision. Some of these phenomena had never been seen before,” says team member and astronomer Renato Dupke.

For experts, having the opportunity to study a structure such as this one may be a once-in-a-lifetime opportunity, given the extremely low odds of something like this happening. The sheer number of interactions between four galactic clusters is baffling experts.

“Like a crash investigator piecing together the cause of an accident, we can use observations of these cosmic pile-ups to reconstruct events that happened over a period of hundreds of millions of years,” says lead scientist Julia Merten.

“This can reveal how structures form in the Universe, and how different types of matter interact with each other when they are smashed together,” the expert adds further. Data from the NASA Chandra X-Ray Observatory and the Japanese Subaru telescope were also used in this research.

“Abell 2744 seems to have formed from four different clusters involved in a series of collisions over a period of some 350 million years. The complicated and uneven distribution of the different types of matter is extremely unusual and fascinating,” lead study author Dan Coe adds.

This discovery is bound to keep a part of the international astronomical community busy for a while. Understanding the intricate interactions that are still occurring in Abell 2744 will take decades.