These Stars Hidden in the Night Sky Might Not be Stars At All but Megastructures

[00:00:00]When we search for extraterrestrial intelligence, we typically look for two things: biosignatures and technosignatures.

[00:00:09]Biosignatures are telltale signs in a planet's atmosphere, such as the simultaneous presence of oxygen and methane, which strongly suggest biological processes.

[00:00:20]Technosignatures are evidence of engineered technology.

[00:00:24]For decades, the search for technosignatures relied almost entirely on radio astronomy.

[00:00:30]Projects under the SETI umbrella point massive dishes at the sky, listening for narrow band radio transmissions.

[00:00:37]However, radio waves attenuate over vast interstellar distances, and a civilization might only use easily detectable radio frequencies for a brief period in its technological development.

[00:00:51]Because of this limitation, physicists have long argued for a different approach based on a universal constant: thermodynamics.

[00:01:01]In 1960, physicist Freeman Dyson published a paper suggesting that to find an advanced civilization, we should look for their waste heat.

[00:01:10]Dyson reasoned that as a civilization advances, its energy requirements grow exponentially. Eventually, they will outgrow the resources of their home planet and require the total energy output of their host star.

[00:01:25]To capture this energy, they would need to construct a massive array of solar collectors orbiting the star, a concept that became known as the Dyson swarm.

[00:01:36]The scale of such an engineering project is difficult to conceptualize, which is part of why astrophysicist Nikolai Kardashev proposed a framework for measuring it in 1964, the Kardashev scale.

[00:01:50]The scale categorizes civilizations by their energy consumption. A type one civilization harnesses all the energy of its planet. A type two civilization harnesses the total energy of its star, and a type three civilization scales this up to harness the energy of an entire galaxy.

[00:02:09]Building a Dyson swarm to achieve type two status around a star like our sun requires a staggering, almost inconceivable amount of raw material.

[00:02:20]Despite the theoretical difficulty, astronomers have actively looked for these structures.

[00:02:26]The most famous instance occurred in 2015 with the observation of KIC 8462852, commonly known as Tabby's Star.

[00:02:37]Data from the Kepler space telescope, which was designed to detect the minute dimming of a star when a planet passes in front of it, revealed that Tabby's Star was dimming erratically.

[00:02:48]Sometimes the light dropped by as much as 22%.

[00:02:52]A Jupiter-sized planet passing in front of a star typically blocks less than 1% of its light.

[00:02:59]The massive, asymmetric dips led researchers to seriously consider the possibility of a partial Dyson swarm or an alien mega structure under construction.

[00:03:10]Subsequent observations, however, ruled out the mega structure hypothesis by analyzing the dimming across different wavelengths of light.

[00:03:18]When the star dimmed, it lost more blue light than red light, a wavelength-dependent pattern that is the exact signature of fine space dust.

[00:03:28]Solid objects like solar panels or spacecraft block all wavelengths of light equally.

[00:03:34]Tabby's Star is likely surrounded by a massive, uneven cloud of dust resulting from a shattered comet or planetesimal.

[00:03:43]The case perfectly illustrates the primary challenge in hunting for Dyson swarms, distinguishing artificial structures from natural dust.

[00:03:52]Both absorb visible starlight and re-emit it as infrared radiation, which is exactly what makes the two so difficult to tell apart from a distance.

[00:04:01]But a recent study refines how and where we should be looking for these structures.

[00:04:06]Previous theoretical work focused heavily on sun-like stars. The new research suggests that a highly advanced civilization would optimize their engineering for longevity and material efficiency, making sun-like stars a poor target. Instead, they would focus on low-mass stars, specifically red dwarfs and white dwarfs.

[00:04:28]Red dwarfs are the most abundant stars in the Milky Way, making up roughly 70% of the stellar population.

[00:04:35]They burn through their hydrogen fuel extremely slowly, meaning their lifespans are measured in trillions of years.

[00:04:42]For a civilization looking to build a permanent energy infrastructure, a red dwarf offers unparalleled stability.

[00:04:50]Furthermore, because they're cooler and smaller than the sun, their habitable zone is much closer to the star, typically between 0.05 and 0.3 astronomical units.

[00:05:02]A civilization could build a Dyson swarm at this close range, drastically reducing the total surface area required and solving the material shortage problem.

[00:05:13]The new models map exactly how these structures would appear to our telescopes, utilizing the Hertzsprung-Russell diagram, or HR diagram, which plots a star's luminosity against its surface temperature.

[00:05:26]Natural stars fall into predictable sequences on this chart based on their mass and age.

[00:05:32]If a Dyson swarm completely encloses a star, the total energy output, the luminosity, remains unchanged because energy cannot be destroyed.

[00:05:42]However, the swarm absorbs the high-energy visible light, utilizes it, and then vents the excess energy as low-frequency infrared waste heat.

[00:05:52]Because the surface area of the swarm is vastly larger than the star itself, this waste heat is emitted at a much lower temperature.

[00:06:02]A typical red dwarf sits in the lower right section of the HR diagram with a surface temperature of around 3,000 K.

[00:06:09]According to thermodynamic models, if that same red dwarf is fully enclosed by a Dyson swarm, the apparent surface temperature drops to roughly 50 K, which is about -223° C.

[00:06:24]This shifts the object far to the right on the HR diagram, placing it in a region where no natural stars exist. To an external observer, the object would appear anomalously faint in visible light while radiating an intense uniform spectrum of infrared energy.

[00:06:44]To confirm such an object is not simply a dust-obscured star like Tabby's Star, astronomers must rely on spectroscopy.

[00:06:52]Natural circumstellar dust disks are rich in silicates. When analyzed with a spectrograph, these dust clouds produce specific emission lines that correspond to silicate chemistry.

[00:07:04]A Dyson swarm, presumably constructed from refined metals, carbon nanotubes, or other advanced synthetic materials, would not produce a silicate signature.

[00:07:15]Astronomers are already applying these parameters to existing astronomical surveys. In 2024, researchers from Uppsala University in Sweden published the results of Project Hephaestus, a dedicated search for Dyson spheres.

[00:07:30]The team analyzed a data set of 5 million stars cataloged by the Gaia, 2MASS, and WISE surveys. They built a custom analytical pipeline to filter out known natural sources of infrared excess, such as young stellar objects, background galaxies, and natural dust clouds.

[00:07:48]Out of 5 million stars, the pipeline identified seven distinct candidates.

[00:07:54]As it turns out, all seven candidates are red dwarfs.

[00:08:00]These objects exhibit a clear anomalous infrared excess that aligns with a thermodynamic profile of a partial Dyson swarm.

[00:08:09]Since then, however, follow-up observations have found that at least one of the seven candidates is likely contaminated by a background galaxy, rather than the star itself. And further research suggests similar contamination could explain the rest.

[00:08:24]So, yeah, it remains entirely possible that the remaining candidates represent an extreme or rare phase of natural dust disk evolution that our current models do not fully account for.

[00:08:37]However, the candidates provide exact coordinates for follow-up observations, and modern astronomy possesses the ideal instrument to investigate them, the James Webb Space Telescope.

[00:08:49]Its highly sensitive spectrometers are capable of targeting these red dwarfs, analyzing their infrared emissions, and searching for the presence or absence of silicate dust.

[00:09:01]By applying the laws of thermodynamics and utilizing comprehensive stellar surveys, astronomers are now conducting galaxy-wide audits of stellar energy output.

[00:09:13]The search for extraterrestrial intelligence has moved beyond listening for radio broadcasts and into something closer to auditing the galaxy's energy budget, star by star.

[00:09:24]JWST is already positioned to check these seven candidates for the telltale absence of silicate dust.

[00:09:31]But the next major leap comes from the Nancy Grace Roman Space Telescope, set to launch in August this year, which will survey vast swaths of the sky with a field of view hundreds of times larger than Hubble's.

[00:09:45]If Dyson swarms exist anywhere in our galaxy, the tools to find them are no longer theoretical.

[00:09:52]They're here.

[00:09:54]What do you guys think?

[00:09:56]Let me know by dropping in your comments below. And as always, don't forget to subscribe to Territory, because this is your space.