Sarthak Dasadia, a physics doctoral student at the University of Alabama in Huntsville, recently identified a massive shock wave emanating from a merging galaxy cluster known as Abell 655.
The shock wave is the second-strongest merger shock — bested only by the Bullet Cluster shock, which astronomers measured in 2006.
The latest wave is moving outward from the merging cluster at a speed of 2,700 kilometers per second — three times the speed at which sound travels through Abell 655.
Increasingly, astronomers are looking to the merging of galaxies and galactic clusters for insights into how large celestial objects form and evolve. Shock waves can reveal characteristics of the inter-cluster environment and the nature of the extremely hot plasma found between the merging clusters.
When galaxy clusters measuring several light-years across are thrown into a slow-motion collision, their cold cores and layers of hot gas are forced together, creating violent turbulence.
“When two cold cores collide, they may create a shock of heated gas,” Dasadia said in a news release. “Such mergers are actually among the most energetic events in the universe, other than the Big Bang itself.”
The shock waves and turbulence produced by merging galaxy clusters aren’t entirely foreign. Meteorologists and marine scientists study similar phenomena — the merging of clusters of disparate temperatures. But models of scale are no substitute for the real thing.
“Technically, we observe the same features in space that we do on Earth,” Dasadia said. “This area has been studied extensively before at small scales, but few had done the work to discover what I found here at such big scales.”