Wednesday, March 25, 2015

Habitability of Possible Exomoons in Observed F-star ExoPlanetary Systems From the Impact of Ultraviolet Light

UV Habitability of Possible Exomoons in Observed F-star Planetary Systems


Sato et al


In the present study we 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 them, 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 different orbits with eccentricities ranging from 0.08 to 0.72. Particularly, we consider the stellar UV environments provided by the photospheric stellar radiation in regard to the circumstellar habitability of the system. According to previous studies, DNA is taken as a proxy for carbon-based macromolecules following the paradigm that extraterrestrial biology might be based on hydrocarbons. Thus, the DNA action spectrum is utilized to represent the impact of the stellar UV radiation. Atmospheric attenuation is taken into account based on parameterized attenuation functions. We 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 in systems of high ellipticity. For some systems large values of damage are attained compared to an Earth-type planet at Earth-like positions in the solar system. A highly protective exomoon atmosphere would be required in most systems to foster habitable environments, notwithstanding extremophiles or systems based on nonstandard exobiology, which are beyond the scope of the present study.

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