A Statistical Estimation of the Occurrence of Extraterrestrial Intelligence in the Milky Way Galaxy

Creators: Cai, Xiang; Jiang, Jonathan H.; Fahy, Kristen A.; Yung, Yuk L.

Abstract

In the field of astrobiology, the precise location, prevalence, and age of potential extraterrestrial intelligence (ETI) have not been explicitly explored. Here, we address these inquiries using an empirical galactic simulation model to analyze the spatial–temporal variations and the prevalence of potential ETI within the Galaxy. This model estimates the occurrence of ETI, providing guidance on where to look for intelligent life in the Search for ETI (SETI) with a set of criteria, including well-established astrophysical properties of the Milky Way. Further, typically overlooked factors such as the process of abiogenesis, different evolutionary timescales, and potential self-annihilation are incorporated to explore the growth propensity of ETI. We examine three major parameters: (1) the likelihood rate of abiogenesis (λ_A); (2) evolutionary timescales (T_(evo)); and (3) probability of self-annihilation of complex life (P_(ann)). We found P_(ann) to be the most influential parameter determining the quantity and age of galactic intelligent life. Our model simulation also identified a peak location for ETI at an annular region approximately 4 kpc from the galactic center around 8 billion years (Gyrs), with complex life decreasing temporally and spatially from the peak point, asserting a high likelihood of intelligent life in the galactic inner disk. The simulated age distributions also suggest that most of the intelligent life in our galaxy are young, thus making observation or detection difficult.

Additional Information

© 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/). Received: 13 December 2020 / Revised: 11 January 2021 / Accepted: 12 January 2021 / Published: 18 January 2021. This research was supported by the Jet Propulsion Laboratory, California Institute of Technology, under the contract with NASA. We acknowledge the partial funding support from the NASA Exoplanet Research Program NNH18ZDA001N-2XRP. We also thank the Virtual Planetary Laboratory at the University of Washington for support. This research was funded by the NASA Exoplanet Research Program NNH18ZDA001N-2XRP. Author Contributions. Conceptualization, J.H.J.; methodology, X.C. and J.H.J.; software, X.C. and J.H.J.; validation, J.H.J., K.A.F., and Y.L.Y.; formal analysis, X.C. and J.H.J.; investigation, X.C. and J.H.J.; resources, J.H.J.; data curation, X.C. and J.H.J.; writing—original draft preparation, X.C. and J.H.J.; writing—review and editing, J.H.J., K.A.F., and Y.L.Y.; visualization, X.C. and J.H.J.; supervision, J.H.J.; project administration, J.H.J.; funding acquisition, J.H.J. and Y.L.Y. All authors have read and agreed to the published version of the manuscript. Data Availability Statement. The data underlying this article are available in the article. For additional questions regarding the data sharing, please contact the corresponding author at Jonathan.H.Jiang@jpl.nasa.gov. Institutional Review Board Statement. This article has been approved for unlimited release by the Document Review Services at the Jet Propulsion Laboratory (JPL), California Institute of Technology. Record: URS297443; Submitted by author: Jonathan H Jiang on 12/13/2020; Document Type: Journal Article; Title: A Statistical Estimation of the Occurrence of Extraterrestrial Intelligence in the Milky Way Galaxy; The JPL clearance number is CL#21-0186. Informed Consent Statement. Not applicable. The authors declare no conflict of interest.

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