The Number of Possible CETIs within Our Galaxy and the Communication Probability among These CETIs

Abstract

As the only known intelligent civilization, human beings are always curious about the existence of other communicating extraterrestrial intelligent civilizations (CETIs). Based on the latest astrophysical information, we carry out Monte Carlo simulations to estimate the number of possible CETIs within our Galaxy and the communication probability among them. Two poorly known parameters have a great impact on the results. One is the probability of life appearing on terrestrial planets and eventually evolving a into CETI ($f_c$), and the other determines at what stage of their host star's evolution CETIs would be born ($F$). In order to ensure the completeness of the simulation, we consider a variety of combinations of $f_c$ and $F$. Our results indicate that for optimistic situations (e.g. $F=25\%$ and $f_c=0.1\%$), there could be $42777_{-369}^{+267}$ CETIs and they need to survive for $3_{-2}^{+17}$ yr ($2000_{-1400}^{+2000}$ yr) to achieve one-way communication (two-way communication). In this case, human beings need to survive $0.3_{-0.298}^{+0.6}$ Myr to receive one alien signal. For pessimistic situations (e.g. $F=75\%$ and $f_c=0.001\%$), only $111_{-17}^{+28}$ CETIs could be born and they need to survive for $0.8_{-0.796}^{+1.2}$ Myr ($0.9_{-0.88}^{+4.1}$ Myr) to achieve one-way communication (two-way communication). In this case, human beings need to survive $50_{-49.6}^{+250}$ Myr to receive one signal from other CETIs. Our results may quantitatively explain why we have not detected any alien signals so far. The uncertainty of the results has been discussed in detail and would be alleviated with the further improvement of our astronomical observation ability in the future.

arXiv commentPublished in ApJ

References in corpus (14)

• Planck 2015 results. XIII. Cosmological parameters
• Cosmic Star Formation History
• The Galaxy in Context: Structural, Kinematic and Integrated Properties
• Characteristics of planetary candidates observed by Kepler, II: Analysis of the first four months of data
• The Star Formation Histories of Local Group Dwarf Galaxies I. Hubble Space Telescope / Wide Field Planetary Camera 2 Observations
• The Galactic Habitable Zone and the Age Distribution of Complex Life in the Milky Way
• An analytical model for the history of cosmic star formation
• A simple model for the evolution of disc galaxies: The Milky Way
• Terrestrial, Habitable-Zone Exoplanet Frequency from Kepler
• The First Planets: the Critical Metallicity for Planet Formation
• Probing the Faintest Stars in a Globular Star Cluster
• The Astrobiological Copernican Weak and Strong Limits for Extraterrestrial Intelligent Life
• Strategies and Advice for the Search for Extraterrestrial Intelligence
• A Quantitative Assessment of Communicating Extra-Terrestrial Intelligent Civilizations in the Galaxy and the Case of FRB-like Signals

Cited by in corpus (3)

• Eta-Earth Revisited II: Deriving a Maximum Number of Earth-like Habitats in the Galactic Disk
• Lotka-Volterra Models for Extraterrestrial Self-Replicating Probes
• SETI in 2022