Jones, B.W.; Underwood, D.R. and Sleep, P.N.
(2004). Extrasolar 'Earths' in habitable zones: targets of opportunity.
In: Beaulieu, J.P.; Lecavelier des Etangs, A. and Terquem, C. eds.
321, Extrasolar planets: today and tomorrow.
Astronomical Society of the Pacific Conference Series, 321.
Astronomical Society of the Pacific, pp. 393–400.
We have shown that Earth-mass planets could survive in variously restricted regions of the habitable zones (HZs) of most of a sample of nine of the 102 main-sequence exoplanetary systems confirmed by 25 September 2003. In a preliminary extrapolation of our results to the other systems, we estimate that roughly a half of these systems could have had an Earth-mass planet confined to the HZ for at least the most recent 1000 Ma. The HZ migrates outwards during the main-sequence lifetime, and so this proportion varies with stellar age – about two-thirds of the systems could have such a planet confined to the HZ for at least 1000 Ma at sometime during the main-sequence lifetime. Clearly, these systems should be high on the target list for exploration for terrestrial planets. We have reached this conclusion by launching putative Earth-mass planets in various orbits and following their fate with mixed-variable symplectic and hybrid integrators. Whether the Earth-mass planets could form in the HZs of the exoplanetary systems is an urgent question that needs further study
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