Fig. 1
Estimates for the outer boundary of the classical habitable zone from previous studies. The red and blue curves show the cloud-free boundaries from Kasting et al. (1993) and Kopparapu et al. (2013), respectively. The results for an atmosphere with 100% CO2 clouds from Selsis et al. (2007) is shown in yellow. This estimate is based on a calculation by Forget & Pierrehumbert (1997), which is additionally marked in the figure.
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