2005ApJ...627..534A

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.