A researcher has proposed a new approach for identifying advanced civilisations elsewhere in the universe. The method involves using powerful telescopes to identify rings of satellites around the home worlds of intelligent aliens. The approach is similar to conventional methods of identifying exoplanets by identifying dips in the brightness of the host star. The study shows how such rings of artificial satellites can be distinguished from normal planetary rings of dust, rock or ice. Red Dwarf stars have been identified as the most promising type of star on which to use the approach. Red Dwarf stars are also a good place to hunt for exoplanets, and are a common type of star to host the planets most likely to harbour life.
The scientific community is getting increasingly hopeful of the imminent discovery of extraterrestrial life. A number of rocky exoplanets in orbit in the habitable zone of their host stars have been identified. The habitable exoplanet catalogue lists 53 such planets, out of which 22 are about the size of the Earth. The TRAPPIST-1 system has seven rocky exoplanets in orbit around an ultracool dwarf star 40 light years away, and liquid water could potentially exist on the surfaces of all these worlds in the right conditions. New evidence suggests that some of the planets in the TRAPPIST-1 system may have even more water than the Earth.
The next generation of space telescopes, including the James Webb Space telescope will allow researchers deeper into the atmospheres of these promising exoplanets, looking for markers of life. The search would be a hunt for atmospheric biomarkers, such as the build up of oxygen in the atmosphere along with the ozone layer because of photosynthesis by plants, or organisms that release methane and nitrous oxide. While such an approach can allow scientists to identify planets which are likely to harbour life, biomarkers alone cannot indicate the technological progress of the life forms on the alien worlds. One approach is to use these next generation of telescopes to identify signs of industrial activity in the atmospheres of the planets.
One of the biggest campaigns to find technologically advanced aliens, the Search for Extraterrestrial Intelligence (SETI), attempted to find evidence of intelligent signals being transmitted across interstellar space. Despite using distributed computing to analyse signals, no aliens were found. There are problems with scanning the skies for radio signals though. Radio emissions from a civilisation similar to the Earth’s would not be detectable at interstellar distances, unless the transmitter was directly aimed at the receiver. Another problem is the short duration for which radio broadcasts were the primary mode of communication. The problem is that radio is likely to be the major form of communication for only a short span of time in the timeline of a civilisation, and is likely to go obsolete within about 150 Earth years. The global communications network primarily works through fiberoptic telecommunication cables now.
Another approach is to identify a Dyson Sphere, that would make a star essentially disappear for a time. A Dyson Sphere is a massive hypothetical structure that harvests the entire energy output of a star, and is the sign of a civilisation more advanced than humans. KIC 8462852, also known as the WTF star, Tabby’s star, Boyajian’s Star and LGM-2 was an interesting candidate for a Dyson Sphere because of sudden dips in the brightness of the star. Eventually, after a sustained campaign of observations, a Dyson Sphere was ruled out around the star, and researchers now believe that there is just a massive ring of dust around the star. Previous searches for Dyson Spheres have also yielded no results. Dyson Spheres, a build up of industrial gases and radio signals are all technomarkers, or technosignatures. These are essentially signs of an alien civilisation, that can be observed from afar.
A researcher from the Instituto de Astrofísica de Canarias (IAC) has proposed a new technomarker for identifying advanced alien civilisations. The research includes a number of simulations, that explore how the light of the host star would interact when a planet with a large number of satellites in orbit around it travels across its path. These patterns form signatures, and could allow researchers to identify technologically sophisticated extraterrestrials. The region around the Earth used by these satellites is known as the Clarke Belt, in honour of Arthur C Clarke, who proposed a satellite communication system or “extra-terrestrial relays”, and wrote a number of science fiction novels as well. Looking for Clarke Exobelts using the next generation of telescopes, is another option available for humans to detect aliens.
However, there are problems with this approach too. First of all, the technique would not work on the low Earth orbit, which is the most popular orbit for satellites today. You would need a considerable build up of geostationary and geosynchronous orbit to detect a ring of such satellites at interstellar distances. The build up of satellites in these orbits are expected to increase with the progress of our own civilisations. These methods could make launches cheaper, including the use of reusable rockets, as well as the construction of a space elevator (a concept that Arthur C Clarke explored in The Fountains of Paradise). It is estimated that by the year 2020, our own Clarke Belt could be observed by alien scientists using the same methods over interstellar distances.
While the approach could be used to find intelligent aliens, the study has implications for the security of humans as well. There is debate within the scientific community on whether establishing contact with an alien civilisation, especially an advanced one is desirable. For those who want humans to remain hidden, a build up of satellites in the Clarke Belt practically broadcasts the existence of an advanced civilisation around Earth. Socas explains, “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.” Because of our satellites, either we could find the little green men, or the little green men could find us. The research has been published in The Astrophysical Journal.