Infrared Astronomy:
Infrared astronomy is a burgeoning field with
implications for many different areas of astronomy. One of the
principal
uses appears mundane at first, the search for cosmic dust. However it
is
this dust that gives birth to stars and provides clues about many
aspects of the
evolution of the Universe. We are each, after all, only cosmic dust
cycled through several stars and loaned to our bodies for a mere one
hundred millionth of the age of the universe. The Caltech/NASA
site and the associated
tutorial give some general background information on infrared and
infrared astronomy. A good technical summary of dust in the Universe is
Astrophysics of Dust,
Volume CS-309, Editors: A. Witt, G. Clayton and B. Draine (2004),
Astronomical Society of the Pacific.
Infrared astronomy is the key to looking for Dyson
Spheres. The principal device used for the Dyson Sphere search
at Fermilab has been the IRAS infrared satellite that flew in the mid
eighties. The
web link is listed below. Links to other related infrared facilities
are also given.
In December, 2005 a Spitzer Space Telescope
team announced the observation of some of the ingredients of life in a
cloud around IRS 46. The Dyson Sphere search tools can be used to look
for similar
nearby objects.
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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.
An unambiguous Dyson Sphere signature could
be
interesting evidence for “cosmic archaeology”, that is signs of
intelligent
activity elsewhere in the Universe. Cosmic archaeology signatures
represent a different approach to finding intelligence elsewhere in the
Universe. Unlike 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] has 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 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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