Dyson Spheres and Interstellar Archaeology  updated December 17, 2010  D. Carrigan carrigan@fnal.

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Dyson Spheres:

In 1960 Dyson (Science 131, 1667 (1960)) suggested that an advanced civilization inhabiting a solar system might break up the planets into very small planetoids or pebbles to form a loose shell that would collect all the light coming from the star. The shell of planetoids would vastly increase the available "habitable" area and absorb all of the visible light. The stellar energy would be reradiated at a much lower temperature. If the visible light was totally absorbed by the planetoids a pure Dyson Sphere signature would be an infrared object with luminosity equivalent to the hidden star and a blackbody distribution with a temperature corresponding to the radius of the planetoid swarm. For the case of the Sun with the planetoids at the radius of the Earth the temperature would be approximately 300 ºK. Many of the earlier searches for Dyson Spheres have looked for so-called partial Dyson Spheres where the loose shell only partially obscures the star. The Dyson Sphere investigation at Fermilab looks for so-called pure Dyson Spheres as well as partial Dyson Spheres. The Fermilab Dyson sphere search was covered in a June, 2008 Fermilab astrophysics seminar.  The article  was published as Astrophysical Journal 698  2075-2086 (2009). It is available online at http://stacks.iop.org/0004-637X/698/2075

The general subject of Dyson spheres is covered in a Scholarpedia web article done with Freeman Dyson at http://www.scholarpedia.org/article/Dyson_sphere

Interstellar Archaeology:

An unambiguous Dyson Sphere signature could be interesting evidence for "interstellar archaeology”, that is signs of intelligent activity elsewhere in the Universe. Interstellar archaeology signatures represent a different approach to finding intelligence elsewhere in the Universe. Unlike most SETI signals generated as beacons, the creation of a Dyson Sphere signature did not require an active strategy on the part of the originating “civilization”. Lemarchand [SETIQuest, Vol. 1, #1, p.3] and Carrigan have reviewed a wide range of other possible signatures of extraterrestrial technological activity. An interesting distinction between SETI searches and systematic searches for objects like Dyson Spheres is that no presumption has to be made concerning the intent or motivation of the originating “civilization”. In this sense a Dyson Sphere search is more akin to a search for extra solar planets.
The subject of interstellar archaeology  was covered in a February, 2010 Fermilab astrophysics seminar. The work has been published as "Starry Messages: Searching for Signatures of Interstellar Archaeology", Richard A. Carrigan, Jr,, Journal of the British Interplanetary Society, 63, 90 (2010). A preprint appeard earlier as astro-ph arXiv1001.5455

The Dyson Sphere search at Fermilab Interstellar Archaeology table
Other Dyson Sphere searches Kardashev scale
Dyson Sphere search exercise for amateurs
Exoplanet atmosphere signatures for intelligence
Dyson Sphere engineering Astroengineering
Other Dyson Sphere sites Galactic scale possibilities
Dyson Sphere Look Alikes
Infrared astronomy