Methods and Results of an Optical Search for Extraterrestrial Civilizations

Abstract

The prospects for searches for optical signals arriving from extraterrestrial civilizations are discussed. Two criteria for an artificial origin for optical emission are analyzed – intensity variations with a a semiotic time structure and the presence of narrow laser lines. We propose to attempt to detect and study these signals by investigating "suspicious" astronomical objects with extremely high time resolution, 10-7 s. We will use the special hardware/software photometric complex MANIA (Multichannel Analysis of Nanosecond Intensity Alterations), which consists of a photometer, a "time - code" converter that is the recording system, a PC/AT 486 computer, and a tape recorder. Special statistical methods and programs for the search and analysis of any type of brightness variability of astronomical objects on time scales from 10-7 – 102s are described. The criteria for choosing objects to be included in the search for extraterrestrial civilizations signals are discussed. We propose to search for Type I civilizations by investigating 161 stars of spectral types F9V-G5V within 25 pc of the Sun. As possible beacons (transmitters) of Type II extraterrestrial civilizations, we propose to consider objects that have unusual characteristics, in particular, lineless optical spectra. The results of observations of 60 objects and the limits for the power of possible signals are reported.