In 1960, Freeman Dyson introduced a visionary concept of advanced civilizations constructing colossal megastructures around their stars to harness their energy and expand their habitable zones. Fast forward to 2015, the astronomical community was captivated when the star KIC 8462852, known as Tabby’s Star, began experiencing perplexing dimming episodes. Though subsequent analysis in 2018 suggested that the dimming was likely due to dust rather than solid structures, Tabby’s Star ignited fascination in the idea of megastructures and their associated technosignatures.
Dyson’s ideas emerged during a time when astronomers were oblivious to the vast abundance of exoplanets in our Milky Way galaxy. The discovery of the first confirmed exoplanet didn’t occur until 1992, and today, we’ve identified a staggering 5,514 exoplanets. Considering this wealth of planetary real estate, a team of researchers from Bangalore, India, has recently proposed an intriguing alternative. Instead of constructing megastructures, advanced civilizations could opt for a simpler and less destructive solution: acquiring planets within their own system or capturing free-floating planets (FFPs) beyond and relocating them into the star’s habitable zone (HZ).
This groundbreaking research was spearheaded by Raghav Narasimha, a physics graduate student at Christ University in Bangalore, India, and joined by Margarita Safonova and Chandra Sivaram, who are respectively a Department of Science and Technology (DST) Woman Scientist and a professor of astrophysics at the Indian Institute of Astrophysics (IIAP) in Bangalore, India. Their preprint paper titled “Making Habitable Worlds: Planets Versus Megastructures” has recently surfaced online and is currently under review for publication in Astrophysics and Space Science.
The problem with megastructures
The notion of advanced civilizations constructing colossal structures to harness their star’s energy has a long history, dating back to the early 20th century. Early examples include John Desmond Bernal’s concept of the Bernal sphere, outlined in his 1929 work, “The World, the Flesh & the Devil.” Bernal proposed that such structures would primarily be built from materials sourced from smaller asteroids, Saturn’s rings, or other celestial remnants, rather than solely relying on Earth’s resources.
Olaf Stapledon expanded upon this idea in his science fiction novel “Star Maker,” where he depicted a future civilization capable of crafting artificial planets in space for permanent habitation. These immense hollow spheres, made of advanced super-metals and transparent adamant, varied in size from small asteroids to spheres larger than Earth. Dyson’s 1960 proposal paper may have drawn inspiration from these concepts.
In Dyson’s seminal paper, “Search for Artificial Stellar Sources of Infrared Radiation,” he posited that civilizations would build what came to be known as a “Dyson sphere” to harness energy and expand their living space. Dyson reasoned that advanced civilizations, observable from cosmic distances, would have evolved to maximize their habitat following Malthusian principles, resulting in the creation of artificial biospheres enveloping their parent stars.
However, Dyson’s calculations were initially limited to our solar system’s habitable space, primarily Earth. Nonetheless, he suggested that celestial bodies, such as Jupiter, held vast amounts of material that could be repurposed for constructing these artificial biospheres. Using Jupiter as an example, Dyson proposed creating a spherical shell around the sun, about 2 to 3 meters thick, with a density of 200 grams per square centimeter.
Dyson also recommended that SETI researchers search for these structures in our galaxy by detecting their heat signatures, specifically in the infrared range of 8 to 10 microns due to excess infrared radiation from the structures’ waste heat.
While astronomers have continued to search for such objects, they have not yet found evidence of Dyson civilizations. An alternative proposal by Narasimha and colleagues involves moving multiple planets within the sun’s habitable zone to increase the livable space in our solar system without destroying planets.
Critics of Dyson’s original calculations and assumptions have pointed out several issues. For instance, Dyson’s idea of using Jupiter as a resource did not account for the fact that only a small portion of Jupiter’s mass (about 13%) could be utilized for construction, as the majority consists of hydrogen and helium, which are impractical as building materials. Additionally, advancements in technology and other factors influencing population dynamics challenge Dyson’s premise based on Malthusian Theory, which predicts that population growth will inevitably outstrip available resources.
Narasimha and his colleagues raise several critical concerns regarding Dyson’s original proposal. One major issue is that enclosing a star like our sun in a Dyson sphere would trap all of its solar wind inside, leading to the disappearance of the heliosphere. This would expose the Dyson sphere to heightened levels of cosmic rays, potentially posing a threat to the biosphere within.
Moreover, their analysis highlights both technical and ethical problems with the concept. Constructing such a megastructure would require utilizing all inner planets and even some of the outer planets, effectively obliterating the familiar solar system, including Earth with its unique biosphere. This contradicts the principles of Planetary Protection, which are established UN policies aimed at preserving celestial bodies within our solar system.
Additionally, in our current solar system, Jupiter’s gravitational influence plays a crucial role in deflecting asteroids, reducing the risk of collisions with Earth. However, a Dyson sphere, or even a ring, would be highly vulnerable to minor disturbances, such as meteorite impacts, potentially resulting in collisions with the central star.
Furthermore, they point out that the interior of a solid Dyson sphere would lack gravity unless it rotates, and even then, gravity would be present only at the equator, equivalent to Earth’s 1 g. This continuous illumination, with no nights, would cause the interior to reflect sunlight with Earth-like albedo, making the sky significantly brighter than a typical day on Earth. Without a natural magnetic field, the Dyson sphere’s inhabitants would be exposed to solar flares, coronal mass ejections, and solar wind with no protection.
Lastly, the immense timescales required to construct a Dyson sphere must be considered. Building such a megastructure would be an enormous endeavor, not accounting for a civilization’s potential long-term stability and sustainability over extended periods, a factor known as the “L parameter” in the famous Drake Equation. Given these circumstances, the practicality and advisability of creating such a megastructure appear highly questionable.
During Dyson’s era, the prevailing assumption was that most stars hosted at least one planet within their systems. Thanks to data gathered by telescopes like Kepler, Hubble, TESS, and the upcoming James Webb Space Telescope, astronomers now estimate there could be a staggering 100 billion planets just in our Milky Way galaxy. Moreover, recent research indicates the existence of possibly a trillion free-floating planets, also known as “rogue planets,” within our galaxy.
The intriguing notion proposed by Narasimha and colleagues is that if these planets could be strategically moved into a star’s habitable zone, it would offer civilizations an exponential increase in living space. These advanced societies could import new planets as needed over time and designate them for various purposes. Crucially, this approach avoids the destruction of entire planetary systems.
They refer to these planets used for industrial and technological purposes as “service worlds.” Remarkably, even free-floating planets could be brought into use as service worlds. The mechanism for moving these planets involves powerful laser arrays, potentially in the Zetawatt or Etawatt (10^24 W) power range, which is already employed in nuclear fusion research. Their calculations suggest that the energy required for this planetary rearrangement would be orders of magnitude less than that needed to dismantle planets like Jupiter for Dyson sphere construction.
Beyond the material advantages, a civilization capable of manipulating planets within its system could also alter the orbital mechanics of these worlds. This idea resonates with Konstantin Tsiolkovsky’s 1895 vision of advanced beings who could adjust daily cycles, year lengths, and seasonal temperatures on their planets at will.
This research naturally prompts questions about how SETI researchers might detect such civilizations and their “technosignatures.” While Dyson proposed detecting megastructures through infrared signatures, Narasimha and colleagues suggest that engineered planetary systems would produce distinct technosignatures. This could include powerful narrowband laser arrays, detectable over vast cosmic distances.
This concept aligns with the work of Prof. Philip Lubin, who suggested that advanced civilizations could be detected by observing “spillover” from laser arrays used for communication, propulsion, or asteroid defense. In fact, NASA’s Technosignature Report in 2018 identified optical communications, laser propulsion, and directed-energy methods as viable technosignatures.
Additionally, Narasimha’s team highlights that engineered systems would exhibit unique profiles compared to natural systems. They propose searching for Strange Exoplanetary Architectures (SEAs) as a search parameter for biosignatures and technosignatures. These SEAs could encompass unusual planet arrangements or systems with multiple Earth-like planets positioned unusually close to their star.
In summary, astronomers are urged to explore Strange Exoplanetary Architectures as part of their SETI efforts. The search for modified or orchestrated planetary systems could unveil the presence of multiple habitable planets, service worlds, and advanced communication infrastructure between them. Perhaps some systems even feature multiple stars, each with its own arrangement of planets to support distinct civilizations. The possibilities are both scientifically compelling and profoundly imaginative.
Source: Universe Today