Key Takeaways:

  • Scientists are searching for signs of alien megastructures by looking for stars with unusual amounts of infrared radiation.
  • They found 7 potential megastructures around M-dwarf stars within 1000 light-years of Earth.
  • These potential megastructures could be Dyson Spheres, giant structures built around stars to capture their energy.
  • Even if such advanced civilizations exist, Dyson Spheres might not be necessary due to potential future advancements in energy efficiency.
  • Building Dyson Spheres would require an immense amount of material, making them a very challenging project.

You can search for proof of extraterrestrial technological civilizations in three different ways. One is to look out for deliberate attempts by them to communicate their existence, for example, through radio broadcasts. Another is to search for proof that they have traveled through the solar system. And a third option is to look for signs of large-scale engineering projects in space.

The third strategy was used by a group of astronomers who looked through data from recent astronomical surveys to find seven potential alien megastructures, or Dyson spheres, “deserving of further analysis.” The journal Monthly Notices of the Royal Astronomical Society publishes their research.

Dyson spheres: astronomers report potential candidates for alien megastructures—here's what to make of it
Tabby’s Star in infrared (left) and ultraviolet (right). Credit: Wikipedia

This detailed research is searching stars for “oddballs”—items that could be alien megastructures. However, the authors are careful not to make any overblown claims. The seven objects belong to a class of stars called “M-dwarfs”—a class of stars that are smaller and less bright than the sun—and are all situated within a light-year of Earth.

The physicist Freeman Dyson first proposed the idea of Dyson spheres in 1960 as a means of allowing a highly developed society to utilize the power of a star. Their structures, which included factories, homes, and floating power collectors, would eventually surround the star almost completely, resembling a sphere.

What Dyson realized is that these megastructures would have an observable signature. In the recent study, the team looked for Dyson’s signature, which is a known excess of infrared radiation. That’s because megastructures would absorb visible light given off by the star, but they wouldn’t be able to harness it all. Rather, they would need to “dump” additional energy as a much longer wavelength of infrared light.

Unfortunately, a lot of other objects, like disks of gas and dust or comets and other debris, can also produce this kind of light. But the seven promising candidates aren’t obviously due to a disk, as they weren’t good fits to disk models.

It is noteworthy to mention another characteristic of the Dyson sphere, which is the star’s visible light dipping as the megastructure moves in front of it. Such a signature has previously been discovered. Tabby’s star, Kic 8462852, generated much excitement because it displayed numerous strange dips in light that might be caused by an extraterrestrial megastructure.

It’s most likely not an extraterrestrial megastructure. Numerous natural explanations have been proposed, including comet clouds traveling through dust clouds. Still, it’s a strange observation. Finding this signature would be a logical next step for the seven candidates.

The case against Dyson spheres

On the other hand, Dyson spheres might not even exist. They are not likely to be there, in my opinion. That’s not to say they couldn’t exist; rather, it’s more likely that no civilization able to construct them would have needed to (unless it was a massive work of art).

Dyson’s reasoning for thinking about megastructures of this kind presumed that highly developed civilizations would need a lot of power. At about the same time, astronomer Nikolai Kardashev proposed a scale based almost exclusively on power consumption to measure how far civilizations had progressed.

This made sense, sort of, in the 1960s. In the past, as technology developed and the population grew, humanity’s power consumption grew exponentially. As a result, people simply projected this growing demand into the future.

However, during the past 50 years—and particularly in the last decade—our world’s energy consumption has begun to grow considerably more slowly. Furthermore, Dyson and Kardashev never explained the purpose of these enormous amounts of power; instead, they assumed (quite correctly) that they would be required to carry out whatever it is that highly developed extraterrestrial civilizations do.

But, as we now look ahead to future technologies we see efficiency, miniaturization and nanotechnologies promise vastly lower power use (the performance per watt of pretty much all technologies is constantly improving).

A quick calculation tells us that we would need a surface area equivalent to one billion Earths if we were to harvest 10% of the sun’s energy at the distance that the Earth is from the sun. And if we had a super-advanced technology that could make the megastructure only 10km thick, that’d mean we’d need about a million Earths worth of material to build them from.

The fact that there are only 100 Earths’ worth of solid material in our solar system presents a serious challenge: in order to construct their Dyson sphere, our advanced extraterrestrial civilization would have to disassemble every planet into 10,000 planetary systems and transport the components to the star. To do it with the material available in a single system, each part of the megastructure could only be one meter thick.

This is presuming that they make use of every element found in a planetary system. If their constructions required a significant amount of carbon, for example, we would have to destroy millions of planetary systems in order to obtain it. It’s a hell of a job, but I’m not saying an extremely advanced alien civilization couldn’t accomplish this.

I’d also strongly suspect that by the time a civilization got to the point of having the ability to build a Dyson sphere, they’d have a better way of getting the power than using a star, if they really needed it (I have no idea how, but they are a super-advanced civilization).

Maybe I’m wrong, but it can’t hurt to look.

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