A gigantic “cold front” hurtling through the Perseus galaxy cluster spans about two million light years and has been traveling for over five billion years, over a third of the age of the universe, longer than the existence of our Solar System. Astronomers expected that such an old cold front would have been blurred out or eroded over time because it has traveled for billions of years through a harsh environment of sound waves and turbulence caused by outbursts from the huge black hole at the center of Perseus.
Chandra X-Ray observations of the central regions reveals evidence of the turmoil that has wracked the cluster for hundreds of millions of years. One of the most massive objects in the universe, the cluster contains thousands of galaxies immersed in a vast cloud of multimillion degree gas with the mass equivalent of trillions of suns. Enormous bright loops, ripples, and jet-like streaks are apparent in the image below. The dark blue filaments in the center are likely due to a galaxy that has been torn apart and is falling into NGC 1275, a.k.a. Perseus A, the giant galaxy and supermassive black hole that lies at the center of the cluster.
The sharpness of the Perseus cold front suggests that the structure has been preserved by strong magnetic fields that are wrapped around it. The comparison of NASA’s Chandra X-ray data to theoretical models also gives scientists an indication of the strength of the cold front’s magnetic field for the first time.
This graphic below shows the cold front. The image above contains X-ray data from Chandra—for regions close to the center of the cluster —along with data from ESA’s XMM-Newton and the now-defunct German Roentgen (ROSAT) satellite for regions farther out. The Chandra data have been specially processed to brighten the contrast of edges to make subtle details more obvious.
While cold fronts in the Earth’s atmospheres are driven by rotation of the planet, those in the atmospheres of galaxy clusters like Perseus are caused by collisions between the cluster and other clusters of galaxies. These collisions typically occur as the gravity of the main cluster pulls the smaller cluster inward towards its central core. As the smaller cluster makes a close pass by the central core, the gravitational attraction between both structures causes the gas in the core to slosh around like wine swirled in a glass. The sloshing produces a spiral pattern of cold fronts moving outward through the cluster gas.
Aurora Simionescu and collaborators originally discovered the Perseus cold front in 2012 using data from ROSAT (the ROentgen SATellite), ESA’s XMM-Newton Observatory, and Japan’s Suzaku X-ray satellite. Chandra’s high-resolution X-ray vision allowed this more detailed work on the cold front to be performed.
The Daily Galaxy via Chandra X-ray Observatory