It probably wouldn’t surprise you to know that if you put a supermassive black hole in the middle of a party, it’ll have a pretty big impact.
We know this is true if the party is actually a galaxy cluster. These are like cities of galaxies, collections of hundreds and sometimes thousands of galaxies all orbiting one another. They make up some of the largest structures in the Universe (called superclusters) and are themselves some of the dominant structures in the Universe.
Galaxy clusters tend to have a lot of hydrogen gas floating around between the galaxies, and it can even be the most massive component of the cluster, outweighing the galaxies themselves. That gas tends to be hot, like really hot, tens of millions of degrees. For a long time this was a mystery, because gas like that should cool pretty rapidly (in a few hundred million years, which is short compared to the age of the Universe).
Artwork depicting the wind of gas blown out by the extremely hot disk of material around a supermassive black hole. Credit: NASA/JPL-Caltech
But now we understand that there’s usually a really massive galaxy in the center of the cluster, and it ...