Thus, life-hosting exoplanets may be rarer than hoped.
If our planet were just a little closer to the Sun, a runaway greenhouse effect would render it unliveable, a climate model suggests. The simulation, which helps to define the inner edge of a star system’s ‘habitable zone’, drastically reduces the fraction of Sun-like stars that might harbour a rocky planet suitable for life, according to some scientists. But others note that the model, although detailed, might be too restrictive because it applies only to Earth-like planets on which water is abundant.
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Taking all these factors into account, the model suggests that the inner edge of the Solar System’s habitable zone is about 142 million kilometres from the Sun, or about 95% of Earth’s average orbital distance.
Hat tip: Bioethics.com