NASA investigated: If aliens harnessed solar power, could we detect them?

Somewhere in the vast expanse of the galaxy, an advanced alien civilization might be tapping into the energy of its star. NASA, always on the frontier of discovery, is curious about whether such activity could be detected.

The space agency, armed with some of the most powerful telescopes known to humanity—and with plans to build even more advanced ones—has begun to consider whether it’s possible to spot the signatures of large-scale solar energy harnessing on distant, Earth-like planets. As our scientists gaze ever deeper into the cosmos, they’re pondering the possibility that an extra society, in need of power, might utilize their star’s nearly limitless energy supply, much like humans are increasingly turning to solar power.

Ravi Kopparapu, a NASA planetary scientist who spearheaded this research published in the Astrophysical Journal, explained to Mashable: “We propose it’s a natural technological evolution that an advanced civilization could make.”

Solar panels, which are primarily made from silicon—a material abundant throughout the universe—are highly reflective. This reflective nature makes expansive solar arrays a potentially detectable target for NASA’s efforts to identify life, whether simple or complex, on planets beyond our solar system, known as exoplanets.

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The team questioned whether a large space telescope, like the forthcoming Habitable Worlds Observatory, might be capable of detecting these solar farms on a planet located as far as 30 light-years away—a distance that, while vast, is still relatively close by cosmic standards. This observatory, often referred to as a “super-Hubble,” would feature a mirror nearly 20 feet (6 meters) across, dwarfing the legendary Hubble telescope’s 7.8-foot (2.4 meters) mirror.

On Earth, the researchers estimate that humanity could satisfy all its energy needs by covering around 2.5% of the planet’s surface with solar panels. If the population were to balloon to 30 billion, this would require about 9% of the land to be covered. But how much of a distant exoplanet’s surface would need to be covered in solar panels for it to be detectable by the “super-Hubble”? The team’s simulations suggested a staggering 23% of an Earth-like planet’s surface would need to be blanketed in these reflective arrays.

“That’s huge,” Kopparapu remarked.

From our perspective, this seems like an unlikely scenario. However, the needs and strategies of another civilization might differ significantly. It’s also possible that a different species wouldn’t require such vast amounts of energy, making sprawling solar farms unnecessary. They could have access to highly efficient technologies or maintain a low population, thereby reducing the need for extensive solar panel coverage.

“A civilization may not need as much energy as we think,” Kopparapu pointed out.

NASA investigated:

Yet, it’s conceivable that an intelligent species on a rocky, desert-like planet similar to Mars might decide to cover a significant portion of its surface with solar panels. In such a world, where hydroelectric power might be scarce or nonexistent, solar energy could be the most viable option. Or perhaps they would have reasons beyond our current understanding for doing so.

“We can’t judge what a civilization’s motives are,” Kopparapu emphasized.

Beyond solar panels, some scientists have speculated for decades about the potential for megastructures designed to surround a star, capturing enormous amounts of stellar energy. These colossal constructs, known as Dyson Spheres, might seem like an impractical choice for a technologically advanced civilization.

“Surely a society that can place enormous structures in space would be able to access nuclear fusion or other space-efficient methods of generating power,” noted Vincent Kofman, a NASA research scientist involved in the study, in an agency statement. (Humanity itself is still striving to achieve nuclear fusion energy, though this technology remains a distant goal.)

Future telescopes, such as the Habitable Worlds Observatory, will be searching for a variety of potential signs of life. Research like this informs scientists about what to look for—be it pollution, life-sustaining atmospheric components, or other technological signatures. While detecting solar panels on a distant world might seem improbable, it’s not outside the realm of possibility. In the search for extraterrestrial civilizations—whether they are exceedingly rare or more common than we imagine—almost anything is possible.

Who knows what these powerful instruments will discover, even light-years away?

“They might even find city lights,” Kopparapu speculated.