Relative likelihood for life as a function of cosmic time

Abstract

Is life most likely to emerge at the present cosmic time near a star like the Sun? We address this question by calculating the relative formation probability per unit time of habitable Earth-like planets within a fixed comoving volume of the Universe, dP(t)/dt, starting from the first stars and continuing to the distant cosmic future. We conservatively restrict our attention to the context of ``life as we know it'' and the standard cosmological model, ΛCDM . We find that unless habitability around low mass stars is suppressed, life is most likely to exist near ∼ 0.1M⊙ stars ten trillion years from now. Spectroscopic searches for biosignatures in the atmospheres of transiting Earth-mass planets around low mass stars will determine whether present-day life is indeed premature or typical from a cosmic perspective.