Potential for life to exist and be detected on Earth-like planets orbiting white dwarfs

Abstract

With recent observations confirming exoplanets orbiting white dwarfs, there is growing interest in exploring and quantifying the habitability of temperate rocky planets around white dwarfs. In this work, the limits of the habitable zone of an Earth-like planet around a white dwarf are computed based on the incident stellar flux, and these limits are utilized to assess the duration of habitability at a given orbital distance. For a typical $0.6 M_\odot$ white dwarf an Earth-like planet at $\sim 0.012$ AU could remain in the temporally evolving habitable zone, maintaining conditions to support life, for nearly 7 Gyr. In addition, additional constraints on habitability are studied for the first time by imposing the requirement of receiving sufficient photon fluxes for UV-mediated prebiotic chemistry and photosynthesis. We demonstrate that these thresholds are comfortably exceeded by planets in the habitable zone. The prospects for detecting atmospheric biosignatures are also evaluated, and shown to require integration times on the order of one hour or less for ongoing space observations with JWST.