A general modeling scheme for assessing the suitability for life on any Earth-like extrasolar planet is presented. This approach is based on an integrated Earth system analysis in order to calculate the habitable zone in main-sequence-star planetary systems. A new attempt by Lineweaver to estimate the formation rate of Earth-like planets over cosmological time scales is applied to calculate the average number of habitable planets in the Milky Way as a function of time. The combination of this results with our estimations of extrasolar habitable zones yields the average number of habitable planets over cosmological time scales. We find that there was a maximum number of habitable planets at the time of Earth's origin.
展开▼
