Cygnus A is the most powerful radio galaxy known to astronomers. Its radio image shows the central nucleus as a red dot between two huge lobes, each of which is roughly the size of our Milky Way galaxy. The lobes are tremendously powerful, emitting about 1 trillion times the luminosity of our Sun (thatΓÇÖs about ten times the lumi- nosity of our entire galaxy). Note that the lobesΓÇÖ edges are red while their inner portions are a ΓÇ£coolerΓÇ¥ blue. Although the red areas are now at the lobe edges, they were not always. Like a hot metal poker pressed into a stick of butter, this hot material ΓÇ£drilledΓÇ¥ its way out from the galaxyΓÇÖs center. The material left behind cooled, eventually forming the blue areas of the radio lobes.
