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Summary: TRANSIT LIGHT-CURVE SIGNATURES OF ARTIFICIAL OBJECTS
Luc F. A. Arnold
Observatoire de Haute-Provence, Centre National de la Recherche Scientifique, 04870
Saint-Michel-l'Observatoire, France; arnold@obs-hp.fr
Received 2005 February 2; accepted 2005 March 23
ABSTRACT
The forthcoming space missions, able to detect Earth-like planets by the transit method, will a fortiori also be able
to detect the transits of artificial planet-sized objects. Multiple artificial objects would produce light curves easily
distinguishable from natural transits. If only one artificial object transits, detecting its artificial nature becomes more
difficult. We discuss the case of three different objects (triangle, two-screen, and louver-like six-screen) and show
that they have transit light curves distinguishable from the transits of natural planets, either spherical or oblate,
although an ambiguity with the transit of a ringed planet exists in some cases. We show that transits, especially in
the case of multiple artificial objects, could be used for the emission of attention-getting signals, with a sky coverage
comparable to that of the laser pulse method. The large number of planets (several hundreds) expected to be
discovered by the transit method by future space missions will allow us to test these ideas.
Subject headinggs: extraterrestrial intelligence -- planetary systems
1. INTRODUCTION
Current Search for Extraterrestrial Intelligence (SETI) pro-
grams concentrate on the search for radio or optical laser pulse
emissions (Tarter 2001). We propose here an alternative approach
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