A University of Alabama in Huntsville (UAH) student has discovered a shock wave in the merging galaxy cluster Abell 655 that is the second strongest ever of its kind, taking a backseat only to the Bullet Cluster shock. The finding was discovered using observations from the Chandra X-ray Observatory.
The shock wave - located to the north of the Abell 655 cluster - is travelling at a speed of 2,700 kilometers per second, which is approximately three times the local speed of sound in the cluster. Scientists are excited by the discovery for its potential to open up doors that will further scientific exploration.
"Studying mergers of galaxy clusters has proven to be crucial to our understanding of how such large scale objects form and evolve," said Sarthak Dasadia, a researcher at the University of Alabama in Huntsville and first author of the study, adding that shocks allow us to study the hot plasma between galaxies.
"This could open a door, where people can do a number of different studies based on what I have found," Dasadia said.
Shock waves in galaxy clusters are already being used for numerous facets of science, including the exploration of dark matter, the magnetic field in intercluster space and particle acceleration in the intracluster medium.
Although the universe is full of ancient galaxy clusters that have mellowed out over time and don't show much activity, the unrelaxed clusters such as Abell 665 are dynamically active and make great candidates for unveiling data on merger features like shock waves.
"These galaxy clusters are not boundary objects," Dasadia said. "They do not have a very well-defined boundary around them."
When massive clusters with undefined boundaries collide, their cold cores and the hot gases that surround them are thrown into chaos, leading to shocks and gas fronts.
"When two cold cores collide, they may create a shock of heated gas," Dasadia said. "Such mergers are actually among the most energetic events in the universe, other than the Big Bang itself."
The collision and resulting shock wave that Dasadia observed took place approximately 3.2 billion years ago, which is the amount of time that it took for its light to reach the Earth.
"It amazes me how long it takes for this information to even reach the Earth," Dasadia says. "Then I am also amazed by our technology, by how much we have advanced in developing the telescopes and equipment it takes to be able to observe and study these interactions."
The findings were published in the March 17 issue of The Astrophysical Journal Letters.
