Astrobiology (general)

Likelihood And Appearance Of Life Beyond The Earth: An Astronomical Perspective

By Keith Cowing
Status Report
May 9, 2024
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Likelihood And Appearance Of Life Beyond The Earth: An Astronomical Perspective
Relative sizes of three planetary systems: HR 8799 (top), the Solar system (middle) and TRAPPIST-1 (bottom). Dot sizes correspond to relative masses, and horizontal distances to orbit sizes, both on logarithmic scales. Stars are yellow, hot planets are red, planets inside the habitable zone are green, and cold planets are blue. For the habitable zone limits, the ‘loose’ definition was adopted; see Section 3. — astro-ph.GA

As of 2023, over 5,500 planets are known to orbit stars other than our Sun. We can measure their sizes and orbital periods, infer their masses and temperatures, and constrain their compositions.

Based on these data, about 1% of extrasolar planets are potentially habitable for life as we know it, implying that of the billions of planets in our Galaxy, some may actually be inhabited, at least by microbes.

However, recognizing signs of alien life forms is a major challenge for current technology, because of the wide range of conditions on extrasolar planets, and because of the wide range of forms that life may take. This chapter reviews observations of exoplanets and discusses astrobiological definitions of habitability and the likelihood of finding life beyond the Earth, both within and outside the Solar system.

Floris van der Tak (SRON / University of Groningen, The Netherlands)

Comments: Book chapter, to appear in First Contact: Aliens and Humans in Contemporary Science Fiction, eds. M. van Dijk, F. Bosman, K. Glimmerveen (Springer). Aimed at audience without professional background in natural sciences

Subjects: Astrophysics of Galaxies (astro-ph.GA)
Cite as: arXiv:2405.05115 [astro-ph.GA] (or arXiv:2405.05115v1 [astro-ph.GA] for this version)
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Submission history
From: Floris van der Tak
[v1] Wed, 8 May 2024 15:12:46 UTC (60 KB)

Explorers Club Fellow, ex-NASA Space Station Payload manager/space biologist, Away Teams, Journalist, Lapsed climber, Synaesthete, Na’Vi-Jedi-Freman-Buddhist-mix, ASL, Devon Island and Everest Base Camp veteran, (he/him) 🖖🏻