A compact radio source usually described as the "core" coincides with the galactic nucleus. Most of the radio emission does not come directly from the well-collimated "jets", but from the broader "lobes" that are found around the jet paths. The plasma in the lobes is believed to have been supplied by the jets over millions of years. In the more powerful radio galaxies, there are usually small, bright radio "hot spots" near the boundaries of each lobe. These hot spots are thought to be where strong shocks form near the ends of the supersonic jet outflow.
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What causes the radio emission seen? The origin of the radio emission from Cygnus A and other radio galaxies was soon identified by UCSD's Geoffrey Burbidge as Synchrotron Emission, light produced by "relativistic" electrons, moving near the speed of light, spiralling around lines of magnetic force. |
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