For decades, scientists have wondered whether advanced alien civilizations might build enormous structures around their stars to capture energy. These hypothetical constructions are called Dyson Spheres, and they remain one of the most fascinating ideas in the search for extraterrestrial intelligence.
Recently, a new study by Amirnezam Amiri explored an intriguing question: If a Dyson sphere really existed, what would it look like to astronomers observing the sky? The answer may be surprising. According to the research, the coldest “stars” in our galaxy might not be stars at all. Instead, they could be enormous alien-built structures hiding the light of their host stars.
This idea opens a new pathway for scientists searching for technological civilizations somewhere in the Milky Way.
The Idea Behind Dyson Spheres
The concept of a Dyson sphere was first proposed in 1960 by Freeman Dyson. Dyson suggested that an extremely advanced civilization might need vast amounts of energy to power its technology. One way to achieve this would be to surround a star with structures that capture most or all of its energy output.
Instead of a single solid shell, modern scientists believe such a system would likely be a “Dyson swarm.” This would consist of millions or even billions of solar collectors orbiting the star, forming a dense cloud of energy-harvesting satellites.
These collectors would absorb the star’s light and convert it into usable energy for the civilization.
In theory, such a system could capture nearly 100 percent of a star’s energy, far more than any civilization on Earth currently uses.
Why Certain Stars Are Better for Megastructures
The study suggests that some types of stars would be much easier for a civilization to surround with a Dyson swarm.
Red Dwarf Stars
One of the most promising targets is the Red Dwarf.
Red dwarfs are the most common stars in the Milky Way, making up about 70 percent of all stars. They are smaller and cooler than our Sun, but they have an important advantage: they burn their fuel extremely slowly.
Some red dwarfs may live trillions of years, far longer than the current age of the universe.
Because these stars are smaller, a Dyson swarm could orbit relatively close to the star—between 0.05 and 0.3 astronomical units (AU). This means the structure would require less material to build compared to one around a large star like our Sun.
For an advanced civilization trying to maximize efficiency, red dwarfs could be ideal power plants.
White Dwarf Stars
Another interesting option is a White Dwarf.
White dwarfs are the dense remains of stars like the Sun after they exhaust their nuclear fuel. When a star becomes a white dwarf, it shrinks dramatically—down to about 1 percent of its original size.
Because of their tiny size, building a Dyson swarm around a white dwarf would require far less material. The collectors could orbit only a few million kilometers from the surface.
Even though white dwarfs are technically “dead” stars, they still release heat and radiation for billions of years, providing a steady long-term energy source.
For a highly advanced civilization, these compact stellar remnants could be extremely practical energy hubs.
How Astronomers Identify Stars
To understand how scientists might detect alien megastructures, we need to look at an important tool in astronomy called the Hertzsprung–Russell Diagram.
The H–R diagram is used to classify stars based on two main properties:
Temperature
Luminosity (brightness)
Stars occupy specific regions on this diagram depending on how hot and bright they are. For example:
Hot, bright stars appear in the upper-left region.
Cool, dim stars appear in the lower-right region.
This diagram helps astronomers understand how stars evolve over time.
But a Dyson sphere would completely change where a star appears on this chart.
Why a Dyson Sphere Would Look Extremely Cold
If a Dyson swarm surrounded a star, it would block most of the star’s visible light.
However, the basic laws of physics still apply—energy cannot simply disappear. According to the Law of Conservation of Energy, the energy absorbed by the megastructure must eventually be released again.
Instead of shining in visible light, the structure would release energy as heat, mostly in the form of infrared radiation.
This would make the system appear much cooler than normal stars.
For example:
A typical red dwarf has a surface temperature of about 3000 Kelvin.
A Dyson sphere might emit heat at only 50 Kelvin.
That is two orders of magnitude colder than ordinary stars.
In the H–R diagram, such an object would appear extremely far to the right side, where temperatures are very low.
Interestingly, no natural stars exist in that region.
This makes extremely cold but still luminous objects very suspicious—and potentially exciting—for astronomers.
Another Clue: A Surprisingly “Clean” Spectrum
Another sign of a possible Dyson swarm is the absence of cosmic dust.
Many young stars are surrounded by dusty disks that produce a characteristic silicate emission signature in their spectrum.
But a Dyson swarm made of engineered panels would not produce this dust signature.
Instead, the star system would appear unusually clean when observed with spectrographs.
This difference could help scientists distinguish between natural objects and possible alien megastructures.
Strange Brightness Patterns
A Dyson swarm would also create unusual brightness patterns.
Unlike a solid shell, a swarm would contain gaps between individual collectors. These gaps might allow some starlight to escape.
As the swarm rotates and the collectors move around the star, the system’s brightness could change in unusual ways.
Astronomers call these changes light curves.
Natural stars usually produce smooth and predictable light curves. But a Dyson swarm could cause irregular or unnatural variations, making the system stand out.
Telescopes Searching for Alien Megastructures
Modern space telescopes are already capable of detecting some of these signatures.
One of the best tools is the James Webb Space Telescope, which specializes in observing infrared radiation. Since Dyson spheres would radiate mainly in infrared light, Webb is perfectly suited for the job.
Another telescope that has already been used for this search is Wide-field Infrared Survey Explorer, often called WISE.
These telescopes scan the sky looking for unusually cold but bright objects that do not behave like normal stars.
Possible Dyson Sphere Candidates
In May 2024, researchers working on Project Hephaistos analyzed a catalogue of five million stars.
They identified seven potential Dyson sphere candidates, all located around red dwarf stars.
After further investigation, one of these objects was ruled out because a Supermassive Black Hole in the background was affecting the observations.
Even after that correction, five possible candidates remain.
While none of them are confirmed alien megastructures yet, they are intriguing enough to deserve closer study with more powerful telescopes.
A New Way to Search for Alien Civilizations
The study by Amiri provides astronomers with a new framework for identifying possible techno-signatures—evidence of advanced technology created by extraterrestrial civilizations.
Instead of looking only for radio signals, scientists can now search for unusual infrared objects that behave like extremely cold stars.
If one of these objects eventually turns out to be a Dyson swarm, it would be one of the most important discoveries in human history.
It would mean that somewhere in the vast expanse of the Milky Way, a civilization has advanced far enough to reshape an entire star system for energy.
Until then, astronomers will continue scanning the sky, watching the coldest “stars” in the galaxy—because one of them might not be a star at all.
Reference: Amirnezam Amiri, Dyson spheres on H-R diagram, arXiv (2026). DOI: 10.48550/arxiv.2602.23270
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