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A radio phoenix is a region of a galaxy cluster emitting radio that is presumed to be the revival of previous radio emission. It is presumed some past event, such as a galaxy merger, created the conditions to produce radio (e.g., plasma in motion that is gaining density and is within magnetic field) and later after the radio emission died down, a more-recent, nearby event recreated those conditions in the same place. The presumption is that the plasma had yet to fully return to its "normal" state, and a lesser effect (from a more distant event) was enough to revive the radio emission to the point that we can detect it.