Alien civilizations with technology on a par with humanity's could be detectable using today's instruments.
A new study suggests that if geostationary satellites are thick enough around an alien world, they could be spotted with telescopes already hunting for undiscovered planets.
Both governments and private corporations on our own world use geostationary satellites — which orbit such that they hover over the same spot on Earth — for science, communications, espionage and military applications.
If advanced alien civilizations loft enough satellites into their own geostationary belts, these spacecraft could create a dense, ring-like structure visible from Earth, according to the study.
Socas-Navarro simulated the presence of belts of geostationary satellites around exoplanets, to see whether they could be detected by instruments like NASA's Kepler space telescope and the agency's recently launched Transiting Exoplanet Survey Satellite (TESS).
He found that the belt would need to be about 0.01 percent full for such spacecraft to detect it, whether populated by many small satellites or a handful of large, city-size objects.