Since physicist Freeman Dyson first proposed the idea in 1960, the hypothetical “Dyson sphere” has become one of the most interesting concepts in extraterrestrial intelligence exploration. Scientists are now envisioning a Dyson “swarm” consisting of countless orbiting structures that capture nearly all of the star’s energy, rather than a single solid shell.
Although this concept has long been discussed theoretically, important questions remain. What would astronomers see if it actually existed? New research by Amirnezam Amiri of the University of Arkansas. Currently available as a preprint on arXiv and scheduled for publication in 2016. universeLet’s explore exactly what these giant structures look like through modern telescopes. The study also identifies the types of stars most likely to host them.
Red dwarfs and white dwarfs are the main targets
One of the most likely candidates is a red dwarf. These small, cold stars are the most common type in the Milky Way, and because they consume nuclear fuel so slowly, they can survive for trillions of years, far longer than the universe has ever existed.
Their relatively small size also makes them attractive from an engineering perspective. According to the study, a Dyson swarm could orbit a red dwarf star at a distance of about 0.05 to 0.3 astronomical units and would require far less construction material than swarms built around large stars like the Sun.
White dwarfs may be even more attractive. These dense stellar remnants are the remaining cores of stars like our Sun that have run out of fuel and collapsed to just about 1% of their original size.
The Dyson group is so compact that it can orbit just a few million kilometers above the star’s surface, greatly reducing the scale of the structures required. White dwarfs also emit energy at a steady rate over billions of years, making them reliable long-term power sources.
How Dyson spheres change the appearance of stars
Astronomers classify stars using the Hertzsprung-Russell (HR) diagram, which plots a star’s temperature and luminosity. Using a Dyson sphere dramatically changes where stars appear on that star map.
This structure would absorb virtually all of the star’s radiation instead of letting visible light escape. Energy cannot simply disappear, so an equal amount of energy must be released into space as heat in the infrared part of the spectrum. In effect, the megastructure would absorb starlight, use that energy for the purpose its builder intended, and radiate the excess as infrared heat.
The star’s total energy output remains the same, but its apparent temperature becomes much lower. HR diagrams use bolometric luminosity (that is, luminosity across the entire spectrum), so the object remains the same luminosity but shifts dramatically toward the cooler side of the diagram.
unique infrared signature
This change in temperature is one of the study’s most shocking predictions. A typical red dwarf star has a surface temperature of about 3000K. However, the effective temperature of the surrounding Dyson sphere may be around 50K, about two orders of magnitude lower.
There are no known natural stars occupying that region of the HR diagram. Any object found there would immediately be an interesting candidate for further investigation.
Another possible clue is the absence of dust. Ordinary stars often exhibit silicate emissions associated with dusty disks. In contrast, the Dyson swarm is made up of radiator panels rather than dust, giving it an unusually “clean” spectrum.
Looking for strange light curves
The study also highlights that it is almost certainly impossible to construct a truly solid-state Dyson sphere. The latest calculations show that the amount of material required is unrealistic, even around relatively small stars.
Instead, advanced civilizations might build swarms of many independent solar collectors, leaving gaps between them or varying their density throughout the structure. When these components orbit around a star, they can cause highly unusual and unnatural changes in brightness that depart from normal stellar behavior.
James Webb and the pursuit of alien megastructures
The James Webb Space Telescope specializes in infrared observations, making it particularly well-suited for exploring these hypothetical structures. Older missions such as WISE are also contributing to this effort.
In May 2024, Project Hephaestus researchers reported seven promising Dyson sphere candidates, all associated with red dwarfs, after examining a catalog of nearly 5 million stars. One candidate was later ruled out because a perfectly aligned supermassive black hole in the background explained the anomalous signal.
Still, there remain five candidates worthy of detailed study. Although not confirmed as an alien megastructure, Amiri’s study provides astronomers with another set of observational clues that may help distinguish between genuine technosignatures and natural cosmic phenomena. If the Dyson group exists somewhere in the Milky Way, future infrared observations may eventually reveal where it is hiding.
