Colossal Cosmic Cold Front –Survived Over 1/3 the Age of the Universe (Weekend Feature)

Perseus Cluster Cold Front

 

A colossal “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.

 

Perseus Cluster

 

Colossal Cosmic Cold Front — “Survived Over 1/3 the Age of the Universe”

An enormous “cold front” of gas of 30 million degrees is hurtling through the Perseus galaxy cluster. It spans about two million light years and has been traveling for over five billion years, over a third of the age of the universe and 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 turbulence caused by outbursts from the huge black hole at the center of Perseus.

 

Its mass equivalent to trillions of suns

Chandra X-Ray observations of the central regions reveal 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.

Magnetic Fields –The Key

The sharpness of the Perseus cold front of “cool” gas 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.

 

Perseus Cluster Cold Front

 

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.

 

 

Cold Fronts Common in Galaxy Clusters

When asked about her thoughts about the possible origin of the cold front and if  any similar cold fronts been detected in other galaxy clusters, astrophysicist Aurora Simionescu, leader of the research team,  replied in an email to The Daily Galaxy: “‘Cold fronts’ are very common in clusters of galaxies. The sharp eyes of the Chandra X-ray observatory has allowed us to find many cold fronts located in the bright centers of galaxy clusters, within a distance of several hundred thousand light years. The Perseus Cluster was the first example where we realized that these structures could go out much further into the outskirts of the system, so the swirling motions that cause these cold fronts extend over scales of several millions of light years. You can think of it a bit like a really really large space hurricane. The Perseus Cluster is the brightest galaxy cluster in X-rays so it was natural that this is where the first discovery of such an extreme phenomenon would happen, just because we can observe it easier, but it’s very possible that there are many other cases out there. In fact, we now think that the clusters Abell 2142, Abell 2029, RXJ2014.8-2430, and Virgo, host these very large cold fronts as well, and who knows how many more have yet to be discovered if we look hard enough.”

New Discoveries in the Perseus Cluster

When asked by The Daily Galaxy if any subsequent discoveries have been made of other fascinating phenomena in the Perseus Cluster, Simionescu replied: “Yes, lots… where to begin! A few years ago we were able to measure the actual velocities of the gas flows in the very central parts of the Perseus Cluster — they are about 100 miles per second, which sounds incredibly fast but it’s actually slower than what we initially expected to find. Unfortunately we did not go far enough from the center to probe the swirling motions on very large scales, but we are working on building new satellites that will be capable of doing that. In the meantime, one of my PhD students discovered this year a shock front in the outer parts of the Perseus Cluster, more than 5 million light years from the center. This is different from a cold front, because at shocks the gas is actually heated up. In fact these shocks at very very large distances from the cluster centers are thought to be responsible for the fact that the intracluster gas is so hot that we can see it in X-ray light — and Perseus is once more paving the way for their discovery.” 

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.

Maxwell Moe, astrophysicist, NASA Einstein Fellow, University of Arizona via Aurora Simionescu, The split in the ancient cold front in the Perseus cluster, NASA and Chandra X-ray Observatory