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Megastructures of type-III civilizations orbiting galaxies

Zaza N. Osmanov

TL;DR

The paper investigates the feasibility and detectability of megastructures associated with Type-III civilizations orbiting galaxies, specifically in regions where galactic radiation is comparable to the CMB. It derives the orbital and energetic requirements for placing a solar-mass megastructure at distances where the Galactic flux does not dominate over the CMB, and demonstrates that such orbits are dynamically and energetically plausible for a highly advanced civilization. Key results include a flux-based constraint $I_G \simeq (\Sigma_0/4)\times (r_d/x)$ leading to $x/R \gtrsim 5.5\times(\Sigma_0/\Sigma_{MW})\times( r_d/r_{MW})\times (R_{MW}/R)$ and an orbital velocity $v \simeq \sqrt{GM/x} \simeq 270\times(\cdot)^{-1/2}$ km s$^{-1}$; energy considerations yield $t \sim 10^5$ yr travel times and $\tau \approx 6\times10^3$ yr to reach Milky Way luminosity under modest growth, indicating feasibility. The study also discusses microlensing as a potential detectability channel, with an angular scale near $\theta \approx 90$ micro-arcseconds at 1 Mpc, suggesting observational prospects for identifying such structures, pending a more detailed analysis. The work frames galaxy-scale technosignatures as a plausible observational target for future SETI efforts.

Abstract

The article discusses the possibility of a Type-III extraterrestrial civilization constructing megastructures around a galaxy in regions where the galactic radiation becomes indistinguishable from the CMB radiation. For a Milky Way-like galaxy, we estimated the corresponding distance from its center at which a solar mass megastructure would need to be placed. We also showed that, from an energetic standpoint, placing such a massive object into orbit poses no fundamental difficulties. The detectability of the megastructure was also addressed.

Megastructures of type-III civilizations orbiting galaxies

TL;DR

The paper investigates the feasibility and detectability of megastructures associated with Type-III civilizations orbiting galaxies, specifically in regions where galactic radiation is comparable to the CMB. It derives the orbital and energetic requirements for placing a solar-mass megastructure at distances where the Galactic flux does not dominate over the CMB, and demonstrates that such orbits are dynamically and energetically plausible for a highly advanced civilization. Key results include a flux-based constraint leading to and an orbital velocity km s; energy considerations yield yr travel times and yr to reach Milky Way luminosity under modest growth, indicating feasibility. The study also discusses microlensing as a potential detectability channel, with an angular scale near micro-arcseconds at 1 Mpc, suggesting observational prospects for identifying such structures, pending a more detailed analysis. The work frames galaxy-scale technosignatures as a plausible observational target for future SETI efforts.

Abstract

The article discusses the possibility of a Type-III extraterrestrial civilization constructing megastructures around a galaxy in regions where the galactic radiation becomes indistinguishable from the CMB radiation. For a Milky Way-like galaxy, we estimated the corresponding distance from its center at which a solar mass megastructure would need to be placed. We also showed that, from an energetic standpoint, placing such a massive object into orbit poses no fundamental difficulties. The detectability of the megastructure was also addressed.

Paper Structure

This paper contains 5 sections, 6 equations, 1 figure.

Table of Contents

  1. Introduction
  2. Discussion and Results
  3. Conclusion
  4. Declaration of competing interest
  5. Acknowledgments

Figures (1)

  • Figure 1: A schematic illustration showing the locations of the galactic center (C) and the megastructure (M). We also show the distances and the differential force ${\bf dF}$, which represents the gravitational force exerted on the megastructure by an infinitesimal region located in the plane of the galaxy.