Climatological and ultraviolet‐based habitability of possible exomoons in F‐star systems

Abstract

BackgroundThe identification of conditions suitable for life is considered a key element of modern‐day astronomy, astrophysics, and astrobiology. This research encompasses the environments of stars of different spectral types and evolutionary status. In this article, we focus on the possibility of habitable moons in selected F‐star systems.Materials and MethodsWe explore the astrobiological significance of F‐type stars of spectral type between F5 V and F9.5 V, which possess Jupiter‐type planets within or close to their climatological habitable zones. These planets, or at least a subset of those, may also possess rocky exomoons, which potentially offer habitable environments. Our work considers eight selected systems. The Jupiter‐type planets in these systems are in notably differing orbits with eccentricities between 0.08 (about Mars) and 0.72. We consider the stellar UV environments provided by the photospheric stellar radiation, which allows us to compute the UV habitable zones for the systems. Following previous studies, deoxyribonucleic acid (DNA) is taken as a proxy for carbon‐based macromolecules following the paradigm that extraterrestrial biology might be based on hydrocarbons.ResultsWe found that the damage inflicted on DNA is notably different for the range of systems studied, and also varies according to the orbit of the Jupiter‐type planet, especially for systems of high ellipticity, as expected. Furthermore, the UV levels in the CLI‐HZs of the F‐type stars are generally more severe than for the solar environment, except for regions beyond the outer limits of the general habitable zones. Particular emphasis was placed on locations akin to Earth‐equivalent (i.e., homeothermic) positions in the Solar System. The general conditions of habitability in F‐star systems are also affected by the rapidness of stellar evolution; nonetheless, based on previous research on the origin of life on Earth, a generally favorable assessment about the overall possibility of life around F‐type stars can be conveyed. For some systems studied here, excessive values of damage are attained if compared to today's Earth or during the Archean eon.ConclusionConsidering that the detection of exomoons around different types of stars will remain challenging in the foreseeable future, we view our work also as an example and template for investigating the combined requirements of climatological and UV‐based habitability for exosolar objects. Further studies for systems of stars with other spectral types and/or other evolutionary status will be considered as part of our future research.