Scientists discovered a vast wave of hot gas in the nearby Perseus galaxy cluster, combining data from NASA’s Chandra X-ray Observatory with radio observations and computer simulations. The researchers say the wave formed billions of years ago, after a small galaxy cluster grazed Perseus and caused its vast supply of gas to slosh around an enormous volume of space.
“Perseus is one of the most massive nearby clusters and the brightest one in X-rays, so Chandra data provide us with unparalleled detail,” said lead scientist Stephen Walker at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “The wave we’ve identified is associated with the flyby of a smaller cluster, which shows that the merger activity that produced these giant structures is still ongoing.”
A wave spanning 200,000 light-years is rolling through the Perseus galaxy cluster, according to observations from NASA’s Chandra X-ray Observatory coupled with a computer simulation. The simulation shows the gravitational disturbance resulting from the distant flyby of a galaxy cluster about a tenth the mass of the Perseus cluster. The event causes cooler gas at the heart of the Perseus cluster to form a vast expanding spiral, which ultimately forms giant waves lasting hundreds of millions of years at its periphery. Merger events like this are thought to occur as often as every three to four billion years in clusters like Perseus.
Galaxy clusters are the largest structures bound by gravity in the universe today. Some 11 million light-years across and located about 240 million light-years away, the Perseus galaxy cluster is named for its host constellation. Like all galaxy clusters, most of its observable matter takes the form of a pervasive gas averaging tens of millions of degrees, so hot it only glows in X-rays.
The researchers also found that the size of the waves corresponds to the strength of the cluster’s magnetic field. If it’s too weak, the waves reach much larger sizes than those observed. If too strong, they don’t form at all. This study allowed astronomers to probe the average magnetic field throughout the entire volume of these clusters, a measurement that is impossible to make by any other means.