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.
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