Seeing Dyson Civilizations

In summary, the circumstellar shells of Dyson civilizations-at temperatures ~300 degrees K and radii ~1 a.u.--can be detected with existing telescopes and state-of-the-art infrared detectors in the 8-13-u window out to distances of several hundred parsecs. But discrimination of Dyson civilizations from naturally occurring low-temperature objects is very difficult, unless Dyson civilizations have some further distinguishing feature, such as monochromatic radio-frequency emission.