Astronomers look for signs of advanced technological civilizations
A new study published in the Astrophysical Journal by Héctor Socas-Navarro, a researcher at the IAC, examines the possibility of detecting hypothetical artificial satellites orbiting other worlds. Socas proposes a new technomarker, characterized by the fact that it could be produced by current technology on Earth. There is a region in space around planets called the “Clarke Belt,” after Arthur C. Clarke, who in 1945 published a paper on the use of geostationary orbits for telecommunications.
For the first time in history, the scientific community is hopeful that finding life elsewhere in the universe will become a reality in the not too distant future. This is due, in part, to the new generation of giant telescopes, currently in the planning stages, with which astronomers hope to conduct detailed analyzes of the atmospheres of planets beyond the solar system. For this reason, researchers are making efforts to investigate evidence for biomarkers of life on these planets. Finding intelligent civilizations or technological capability, however, seems much less likely. To begin with, researchers lack “technical markers,” the analogs of biomarkers, that reveal the presence of technology. Since the 1980s, there have been searches for radio signals from other civilizations, so far without success. This is not surprising since radio emissions from a society such as ours would not be detectable at interstellar distances unless deliberately focused in the direction of the receiver. In the scientific literature, there have been proposals to search for technical markers, for example, the so-called “Dyson Spheres”, hypothetical artificial megastructures built around a star to collect its light and thus supply the energy of a civilization much more advanced than our own. .
The publication presents a variety of simulations of “Clarke exobelts” to investigate the possible footprint they would leave in the light of the parent star as the planet transits its disk. The optimal conditions for observing them are found for planets orbiting red dwarf stars, which are also the best places to look for exoplanets in general.
The article published in the Astrophysical Journal describes how these artificial belts can be distinguished from natural rings. Using this technique, current projects and space missions designed to detect exoplanets and their moons and rings could also be used to detect this marker. “We have to keep our eyes open, in case we detect such traces in the data,” says Héctor Socas
Earth’s Clarke Belt, consisting of geostationary and geosynchronous satellites, is not dense enough to be detected at interstellar distances, at least with our current observing capabilities. About two-thirds of existing satellites are in the so-called “low orbit” region, meaning the first few hundred kilometers above Earth, where space debris is already a major problem. T
The Clarke Belt orbit is 36,000km above Earth, and is currently much less populated, but the paper shows that in recent decades, the density of satellites in these orbits has been growing exponentially. If this rate continues, our Clarke Belt would be detectable from other stars by the year 2200.
The speed could even be accelerated if the cost of access to these orbits were lower, for example, with new reusable rockets or by building a future space elevator. Or it could slow down if technological advances lead to other priorities. In any case, there is an active debate about whether humanity should send messages into space or whether we should listen discreetly without revealing our presence. “In this context, the exponential increase in our satellite population could become a telltale sign, whether we like it or not. This is a point that needs to be taken into account in this debate,” says Socas.
Asked if we will one day discover a Clarke Exobelt and therefore find an extraterrestrial civilization, the researcher says: “It seems unlikely, but it costs nothing to look. It’s like someone giving you a lottery ticket. You know it’s highly unlikely you’ll win, but since you have it, you can check the result, just in case.”