The Grand Unification: Active Galactic Nuclei

Abstract

The clue to understanding radio galaxies and quasars lies in their remarkable radio emitting jets. It’s all a matter of perspective. Long, narrow streams of highly energetic gas squirt from the center of a galaxy, emitting radio waves as they go. The radio jet in NGC 6251 is dramatically shown in radiograph form in Figure 12.1. It is 1.2 million light-years in length, which makes it the straightest and longest known object in the universe. The jet is a conduit along which energetic material carries energy and magnetic fields from the nucleus of the galaxy to the outer radio lobes. How are these jets formed and what holds them together? For the jets to be so long and straight a good “memory” is required, something that allows the flowing material to maintain a uniform direction for a very long time, a million years or more, which would be the travel time of some of the jets if the matter flowed at the speed of light. But how fast is that material flowing? Where does the energy come from that enables them to illuminate radio lobes a million light-years away? To rephrase this, what inflates the radio lobes?