Dyson spheres are hypothetical megastructures that an alien civilization builds to use all the energy of its star. However, it is very difficult for us to recognize them, and especially to distinguish them from natural astronomical objects.
Dyson spheres and red dwarfs
Scientists continue to search for alien civilizations in space. And one of the main ways to do that is by searching for Dyson spheres. But recently, researchers have noticed that their external resemblance to quite natural objects prevents them from doing so.
The Dyson sphere itself is a giant structure with a diameter close to the orbit of a planet receiving as much light as Earth. In order to capture the energy of the star they, according to those who seek them, must be built. It is believed that an advanced civilization would require it in much larger quantities than ours.
However, seeing them by themselves at cosmic distances is still almost impossible. The best way to do this is in the infrared range, because they emit excess energy there. However, in such cases they become like red dwarfs, but this is only at first glance.
In truth, it is possible to distinguish between these two types of objects. We do know exactly what the red dwarf itself looks like and its typical emission spectrum. So anything different is something interesting.
Hephaistos project and quasars
Excited by this opportunity, the scientists founded the Hephaistos project. Its essence was to collect data from the astronomical satellites Gaia, 2MASS and WISE, working specifically in the infrared range.
In total, about 5 million objects were analyzed and among them scientists found 7, which spectra were very different from small red stars. They rushed to announce them as candidates for the Dyson sphere.
In truth, other astronomers urged them to take their time. They found that they could be quasars, i.e. black holes actively absorbing and ejecting matter. If the galaxies in which they are located are covered in dense dust clouds, they should look like this.
Hence, a new problem arises in the search for Dyson spheres: how to distinguish them from dust-shadowed quasars. The researchers suggest that rather than proving each case separately, they first investigate existing active black holes to understand their spectra and immediately rule them out in future explorations.
According to phys.org
