Formulation and Resolutions of the Red Sky Paradox

TL;DR

This paper investigates the apparent scarcity of observable red dwarf stars despite their abundance and potential for hosting habitable planets, proposing probabilistic models and possible resolutions to the Red Sky paradox.

Contribution

It formulates a Bayesian framework to analyze the Red Sky paradox and outlines multiple potential resolutions, guiding future observational strategies.

Findings

Red dwarfs are numerous and long-lived but rarely observed as hosts for complex life.

Proposed resolutions include observational biases, planetary habitability limits, and stellar evolution effects.

Future surveys could support or refute these resolutions based on planet occurrence and habitability data.

Abstract

Most stars in the Universe are red dwarfs. They outnumber stars like our Sun by a factor of 5 and outlive them by another factor of 20 (population-weighted mean). When combined with recent observations uncovering an abundance of temperate, rocky planets around these diminutive stars, we're faced with an apparent logical contradiction - why don't we see a red dwarf in our sky? To address this "Red Sky paradox", we formulate a Bayesian probability function concerning the odds of finding oneself around a F/G/K-spectral type (Sun-like) star. If the development of intelligent life from prebiotic chemistry is a universally rapid and ensured process, the temporal advantage of red dwarfs dissolves softening the Red Sky paradox, but exacerbating the classic Fermi paradox. Otherwise, we find that humanity appears to be a 1-in-100 outlier. Whilst this could be random chance (resolution I), we outline three other non-mutually exclusive resolutions (II-IV) that broadly act as filters to attenuate the suitability of red dwarfs for complex life. Future observations may be able to provide support for some of these. Notably, if surveys reveal a paucity temperate rocky planets around the smallest (and most numerous) red dwarfs then this would support resolution II. As another example, if future characterization efforts were to find that red dwarf worlds have limited windows for complex life due to stellar evolution, this would support resolution III. Solving this paradox would reveal guidance for the targeting of future remote life sensing experiments and the limits of life in the cosmos.