Abstract: Interstellar archaeology, searching for cosmic-scale signatures of intelligence, is a different way to look for intelligence beyond our solar system. Unlike most radio SETI approaches, interstellar archaeology does not require intent to communicate on the part of the sender. Interstellar archaeology signatures include non-natural planetary atmospheric constituents, stellar doping, and signatures of astro-engineering. An interesting example of a possible interstellar archaeology artifact is a Dyson sphere, a shroud around a star to harvest the visible light coming from the star. The shroud converts the visible light output to infrared. A Dyson sphere is an illustration of a so-called Kardashev Type II civilization, one that exploits the energy of a star. A Type III civilization would utilize the energy of a galaxy. One way to construct a Type III civilization would be to convert many of the stars in a galaxy to Dyson Spheres. Interestingly, going from one Dyson sphere to many millions is a matter of replication and slow, reasonably tractable space travel. A spreading Dyson sphere-based galactic civilization might give rise to voids of visible light with corresponding increased infrared emission hotspots. Elliptical galaxies, more uniform than spiral galaxies, are logical places to look for these “Dyson-Annis voids” of visible light. This presentation reviews a search for stellar Dyson spheres using data from the IRAS space telescope that operated in the eighties. Searches of several nearly circular elliptical galaxies for Dyson-Annis voids will also be discussed. So far no interesting candidates have been found. These early searches illuminate both the opportunities and challenges involved with the interstellar archaeology approach. With few exceptions interstellar archaeological signatures are clouded. However SETI for so-called cultural transmissions and planetary atmosphere signatures are within reach.
A Search for Dyson Spheres using IRAS
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