These cosmic megastructures could be a giveaway for intelligent alien life
A team of researchers is on the hunt for advanced alien civilizations in the Milky Way.
But the Ph.D. student at Uppsala University’s Department of Physics and Astronomy is not just searching for any alien life. He’s trying to find an alien civilization so advanced that they are able to harness the power of a star through a megastructure known as a Dyson sphere.
“That's the thing that my first project tried to answer, how likely is to find a Dyson sphere in the galaxy,” Suazo tells Inverse. “That’s complicated, but not impossible.”
In a paper presented at the annual meeting of the European Astronomical Society held in July, Suazo explored the potential for Dyson spheres across the Milky Way galaxy.
From his research, Suazo saw at least five stars that could potentially house a Dyson sphere.
What is a Dyson sphere?
A Dyson sphere is a theoretical megastructure built around a star to harness its energy output, first proposed by physicist Freeman Dyson in a paper published in 1960.
In the paper, Dyson presented Dyson spheres as a solution to the growing energy needs of a hyper-advanced alien civilization to sustain its existence. The civilization would employ space-based stellar energy harvesting swarms around their host star — and possibly other stars surrounding it — to feed their energy outlets.
Dyson based his proposal on the fact that a planet only receives a small fraction of the energy produced by its host star. For instance, Earth only receives about one-billionth of the Sun’s total energy output. But by creating a space-based structure, a civilization could meet its energy needs to push its technologically advanced society to the next level.
Dyson also proposed that the search for extraterrestrial intelligence (SETI) programs should “search for sources of infrared radiation” to “accompany the recently initiated search for interstellar radio communications.”
WHAT’S NEW — Using data gathered by Gaia, a space-based telescope launched by the European Space Agency in 2013, and NASA’s WISE, a wide-field infrared space telescope, the team surveyed the Milky Way for potential Dyson sphere-hosting stars.
But rather than the model first envisioned by Dyson himself, the understanding of Dyson spheres nowadays is more of a swarm of satellites or solar panels around a star.
In order to search for Dyson spheres, the team looks for the properties of the star itself. A star produces radiation, and if a star is blocked by some sort of structure then the radiation would decrease. Instead of producing optical radiation, a star with a Dyson sphere around it will then emit radiation in the mid-infrared wavelength with temperatures between 100 to 600 Kelvin.
The Dyson sphere will also glow.
Their survey classified Dyson spheres into four categories:
- Cool Dyson spheres, ones with stars that have temperatures below 200 Kelvin
- Intermediate spheres, with temperatures somewhere between 100 to 600 Kelvin
- Perfect cases, with high temperatures that make them easily detectable
- Transparent Dyson spheres, ones with a few solar panels that make them hard to detect
The transparent Dyson spheres are the most difficult to detect since they have a small number of structures in the swarm, and therefore somewhat invisible.
“The transparent scenario would be when they are just starting the project, when the civilization would have assembled a few solar panels,” Suazo says. “Of course we cannot see that, it will look like a normal star because you won’t get any signal.”
The team identified five sources that could potentially host a hyper-advanced alien civilization based on the temperature and how many solar panels could be covering the star.
If Dyson spheres do exist around those stars, scientists could potentially be able to detect them.
“If they have high covering factor, like a lot of solar panels, and they have temperatures of 200 Kelvin, then yes we could detect them,” Suazo says. “But it really takes work to look for candidates.”
Suazo suggests coming up with a more efficient method to search for stellar candidates by eliminating non-reliable data and only investigate ones with high-quality data.
WHY IT MATTERS — The search for Dyson spheres in the Milky Way could finally answer humanity’s biggest question: Are we alone in the universe?
“It would change our perspective on our place in the universe,” Suazo says.
Not only would humanity know that we’re not alone, but it could also help us design our own Dyson spheres. But in order to develop the proper technology, the human civilization likely needs another 100 to 200 years, according to Suazo.
WHAT’S NEXT — Suazo and his team now want to do follow-up observations for the potential sources of Dyson spheres using the Nordic Optical Telescope located in the Canary Islands.
“We will be looking at the specific sources that are promising, but it’s going to take time,” Suazo says.
Abstract: Dyson spheres are hypothetical structures that high-level civilizations may have built up to harvest the energy of their host star. As in any thermodynamic process, the conversion of stellar energy would involve the emission of waste heat that would be emitted as infrared radiation. If we picture a Dyson sphere as a swarm of smaller satellites collecting the energy from its host star, a broad family of partial Dyson spheres with different covering factors seems plausible. At the same time, these partial Dyson spheres would block some of their host stellar light, leading to a drop in their optical fluxes. Nowadays, we count on missions that have mapped the sky in the optical as well as in the mid-infrared, specifically Gaia and WISE. Both together provide magnitude measurements for roughly 10^7 - 10^8 stars in the galaxy and can recover the two signatures mentioned above. Using this data we estimate how many stars are compatible with Dyson spheres based on Dyson sphere models with temperature ranges between 100-1000 K. In this work, we identify four different scenarios: transparent Dyson spheres, Cool Dyson spheres, intermediate states, and perfect cases.