THE PROSPECTS FOR EARTH-LIKE PLANETS WITHIN KNOWN EXTRASOLAR PLANETARY SYSTEMS

We consider the possible existence of habitable Earth-like planets in four recently discovered extrasolar planetary systems. Such prospectiv e planets must have orbits that are (1) dynamically stable, and (2) al low for surface temperatures compatible with liquid water. We find tha t three of the four new systems (51 Peg, rho(1) Cnc, and 47 UMa) are e asily capable of supporting habitable planets. The fourth (70 Vir) is capable of having a habitable planet only under rather extreme circums tances. To obtain these results, we develop a probabilistic formulatio n for the coupled problem of orbital stability and planetary habitabil ity.