Brightest Cluster Galaxies

At the center of most clusters sits an enormous Brightest Cluster Galaxy (BCG) — a giant elliptical that has grown by cannibalizing smaller galaxies over billions of years. A BCG can hold trillions of stars and outweigh the Milky Way ten times over.

The BCG in the Perseus Cluster sends sound waves through the surrounding hot gas — cosmic bass notes far too low for human ears. These waves carry energy into the intracluster medium, keeping the gas from cooling and forming too many new stars.