New research suggests a way to identify possible Dyson swarms: look for extremely cold objects in the infrared, without signs of dust, around red dwarfs and white dwarfs
Since physicist Freeman Dyson introduced the idea in 1960, the "Dyson sphere" has become one of the most sought-after possible technological signatures in the search for advanced alien civilizations.
The basic idea is that a civilization far more advanced than ours could surround its star with a "sphere" (or in our more modern understanding, a "swarm" of smaller components) in order to capture almost all of the star's energy. Such a structure is theoretically possible, but astronomers still face an important question: what would it look like from Earth?
A group of researchers from the Korea Institute of Geoscience and Mineral Resources (KIGAM) in a preprint published on the arXiv website examine this question and identify the type of stars in which it is most worthwhile to look for Dyson clusters.
Small stars are better targets.
One promising category is red dwarfs. These are the most common stars in the Milky Way, and they use up their nuclear fuel very slowly, so they can last for a very long time. Some are expected to last trillions of years, much longer than the current age of the universe.
Because they are also much smaller than the Sun, a Dyson swarm can be placed about 0.05 to 0.3 astronomical units from the star's surface, reducing the amount of material needed to build it.
White dwarfs can be even more attractive from an engineering perspective. They are the cooled, dense remnants of stars like the Sun, compressed to a tiny size with a radius of about one percent of the original star. Around a white dwarf, a Dyson swarm can orbit within just a few million kilometers of the star's surface, so building a huge structure that collects energy is much less demanding than building one around a larger star. White dwarfs can also emit energy steadily for billions of years, and could be potential reliable long-term energy sources.
The starlight will turn to heat.
But what would stars surrounded by such megastructures actually look like? Astronomers typically use a tool called the HR (Hertzsprung-Russell) diagram to classify stars by their temperature and luminosity. But because a Dyson sphere would block all of a star’s natural light, it would completely change its place on the diagram.
Energy cannot be created or destroyed, so the sphere itself would have to emit exactly the same amount of radiation as the star puts into it. It just does so in the form of heat, or infrared light. So you can basically think of a Dyson sphere as a shell that absorbs the star's light, does something useful with that energy, and then emits it as heat.
When the ball does this, it shifts the star's position all the way to the right, where the low temperatures are mapped on the diagram. The luminosity itself doesn't change at all, it's just shifted to the left, and since HR diagrams use bolometric luminosity (i.e., the luminosity across all spectra), it will appear in the same vertical place on the diagram as its host star, whether it's a red dwarf or a white dwarf.
But the important thing is how far to the right the star is offset. The surface temperature of a typical red dwarf, which lies in the lower right corner of the HR diagram, is around 3,000 degrees Kelvin. The temperature of a Dyson sphere orbiting a star would be 50 degrees – two orders of magnitude lower. There are no natural stars in this region, so any such body would be of great interest as a potential Dyson swarm.
Strange signals will stand out.
Another factor that contributes to the possibility that a body is a Dyson swarm is the absence of dust. A star without a Dyson sphere would typically show a spectral line of silicate emission that is often associated with dark disks. But there is no dust around the radiator plates, so they would appear very "clean" to a spectrograph monitoring them.
It should be noted that in the “swarm” methodology, there will likely be gaps between some of the solar collectors, or varying thickness in certain parts of the swarm. This is so that the material requirements are truly physically possible – modern calculations show that even with a relatively small radius, a real full Dyson sphere is not physically possible. If these small gaps exist, the star will behave very unstable, with unnatural light curves as the structure rotates.
For the scientific article: DOI: 10.48550/arXiv.2602.23270
Short FAQ
What is a Dyson swarm?
A hypothetical array of satellites or facilities that orbit a star and collect a large portion of its energy.
Why would he look "cold"?
Because the energy absorbed from the star's light will be re-emitted mainly as heat in the infrared range, the observed temperature will therefore be very low.
Which stars are the best candidates?
Mainly red dwarfs and white dwarfs, because they are small, relatively stable, and allow the construction of a Dyson swarm at smaller distances and with lower material cost.
Have candidates been found yet?
According to the article, the Hephaistos project identified seven strong candidates in 2024, and after disqualifying one of them, several more candidates remained that require follow-up observations.
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