Wednesday, August 01, 2018 by Edsel Cook
A Spanish researcher made an argument that the search for intelligent alien life should concentrate on looking for signs of a “Clarke Exobelt,” a densely populated belt of artificial satellites surrounding the home planet of a hypothetical advanced alien civilization. In his recently published paper, he believed that this technological marker could be spotted by a new generation of large telescopes, an article in Science Daily stated.
Earlier efforts to detect alien civilizations focused on the radio emissions produced by a technologically advanced culture such as humankind. Decades of listening for electromagnetic signals have not produced any results, so researchers are considering other potential markers for alien life.
Instituto de Astrofísica de Canarias (IAC) researcher Hector Socas brought up a different technomarker that can be generated by a civilization on at least the same technological level as humankind. He pointed out that a certain region of space around Earth – the so-called Clarke belt – contained many geostationary and geosynchronous satellites that provide various services to people on the planet.
Socas simulated a number of Clarke belts that contained various population levels of such satellites. He studied the effect of these denser rings of artificial satellites on the light of different stars as the planet transited across the disk of its parent star.
Based on the results of his simulations, he reported that the transit effect would stand out the most against the backdrop of red dwarf stars. These happen to be the most numerous kind of star, which makes them the best candidates for hosting exoplanets.
An advantage of targeting Clarke belts is the technique’s ease of adoption by existing projects and missions. Instruments with the power and sensitivity to spot exoplanets, moons, and ring systems will be able to spot the Clarke belt of an alien civilization.
Examples of these instruments are the soon-to-be-retired Kepler space observatory and its ground-based counterpart, the High Accuracy Radial velocity Planet Searcher (HARPS) spectrograph in Chile. These two observatories accounted for a good percentage of the exoplanets found in the recent decade.
“It is a search which we will have for nothing,” said Socas, who published his findings in the science journal The Astrophysical Journal. “We have to keep our eyes open, just in case we detect this traces in the data.” (Related: Scientist believes advanced alien civilization inhabited our solar system long before humans came along.)
As it currently stands, humankind’s Clarke belt is not dense enough to be detectable by current levels of human technology at interstellar ranges. Two out of every three human satellites are found in low orbit, just a few hundred miles over Earth.
In comparison, the Clarke belt orbit is 22,369 miles (36,000 km) over Earth. It is much roomier and has far fewer occupants.
However, the IAC paper also noted that the number of satellites in the belt is increasing at an exponential rate. If it maintained the current level of population growth, humankind’s Clarke belt would show up at interstellar distances starting in 2200.
Furthermore, current and future developments could change the timetable of the Clarke belt’s visibility. If it became cheaper and easier to access the orbital region via reusable rockets or similar technologies, the belt could fill up much faster and start showing up on alien instruments ahead of time.
“In this context, the exponential increase in our population of satellites could end up by becoming a signal which gives us away, whether we like it or not. This is a point which should be taken into account in this debate,” said Socas.
Follow the search for the Clarke exobelt of alien civilizations at Space.news.