A search for laser light from the directions of Alpha Centauri A and B was performed by examining 15362 optical, high-resolution spectra obtained between 2004 and 2018. None of the spectra exhibit laser emission lines. The threshold was 10% of the continuum intensity of the spectra of both stars at all wavelengths between 3850 and 6900 {\AA}. This search would have revealed optical laser light from the directions of Alpha Cen B if the laser had a power at least 1.4 to 5.4 MW (depending on wavelength) and was positioned within the 1 arcsecond field of view (projecting to 1.3 AU), for a benchmark 10-meter laser launcher. For Alpha Cen A, the laser power must be 3 times greater for detection. Lasers of smaller aperture would also have been detected but would require more power. Considering all optical surveys, a growing desert is emerging in the search for extraterrestrial technology.
Cite
@article{arxiv.2211.11756,
title = {A Search for Optical Laser Emission from Alpha Centauri AB},
author = {G. W. Marcy},
journal= {arXiv preprint arXiv:2211.11756},
year = {2022}
}