A high school student from Turkey became interested in the following question: what if advanced extraterrestrial civilizations used not the radiation of their stars as an energy source, but their rotational angular momentum? Would we then be able to detect them from a great distance?
Dyson Spheres
It is believed that an advanced extraterrestrial civilization would require truly enormous amounts of energy for its activities. The best source of that energy would be the radiation of its own star. To collect it efficiently, scientists have proposed building gigantic structures around the star known as Dyson spheres.
The concept is interesting because, if Dyson spheres really exist, we could theoretically detect them using existing telescopes simply by looking for stars that emit significantly more energy in the infrared spectrum than they should, given their mass and their brightness in the visible and ultraviolet ranges. However, Рhys.org reports that this may not be the best way to search for advanced civilizations.
The discussion concerns a paper by Turkish high school student Şahin Torlakçı that recently appeared on the arXiv preprint server. In it, the author correctly notes that constructing a Dyson sphere would require an incredibly large amount of material. In addition, preserving the structural integrity of such a construction would be extremely difficult, regardless of the strength of the material used.
That is why detecting extraterrestrial civilizations through Dyson spheres is extremely difficult: they may simply not build them. However, there is another way to obtain a gigantic amount of energy from a star, and it could also potentially reveal the location of extraterrestrials.
Rotational Angular Momentum
Torlakçı believes that extraterrestrial civilizations could use the rotational angular momentum of their stars. After all, every star is not only a thermonuclear reactor, but also a gigantic sphere of extremely dense gas that rotates. In other words, a civilization could effectively consume the rotation of its own star.
Of course, it would not be possible simply to attach a turbine to the Sun or any other star. However, there are several ways to extract rotational momentum indirectly. The first is based on using the energy of Alfvén waves in the star’s corona. If they are made to interact with a conductor, the conductor will begin extracting energy from them, and the source of that energy is the rotation of the star itself.
Another method would involve having a conductor interact directly with the star’s magnetic field through the Lorentz force. At the same time, under Newton’s second law, a reaction force would arise that would slow the star’s rotation.
In general, there may be many ways to use a star’s rotational angular momentum. However, over tens of millions of years, all of them should lead to a relatively rapid decrease in the star’s rotation rate, something that does not occur under natural conditions. It is precisely this difference that astronomers on Earth could notice.
Torlakçı has already carried out his own study. He used a dataset from the Kepler space telescope and identified 6,725 stars in the Milky Way whose spectral class is similar to that of the Sun. Among them, two were found to rotate abnormally slowly. The author does not claim that extraterrestrials must be present there, but he believes these stars deserve closer attention in the search for alien radio signals.
