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
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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
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