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S. Franck, C. Bounama, W. von Bloh (Potsdam Institute for Climate Impact Research), M. Cuntz (University of Texas at Arlington)
We investigate whether Earth-like planets could on principle exist on stable orbits in the habitable zone of extrasolar planetary systems. Such a configuration is described as dynamically habitable. Our definition of habitability does not just depend on the parameters of the central star, but also on the properties of the planetary climate model. In particular, habitability is linked to the photosynthetic activity of the planet, which in turn depends on the planetary atmospheric carbon dioxide concentration, and is thus strongly influenced by the planetary geodynamics. This leads to additional spatial and temporal limitations of habitability, as the HZ becomes narrower with time due to the persistent decrease of the planetary carbon dioxide concentration. To estimate the orbital stability of hypothetical terrestrial planets, recent studies investigating the effects of the giant planets in such systems, have been taken into account. The system 47 UMa has been identified to host two Jupiter-mass planets at respectable distances from the host star, which has properties very similar to those of our Sun, including mass, effective temperature, spectral type, and metallicity. The star 55 Cnc has an outer planetary companion orbiting at about Jupiter distance and two inner giant planets at very small orbits. We show that the existence of a dynamically habitable Earth-like planet is principally possible in both systems (Cuntz et al. 2003, von Bloh et al. 2003). This likelihood depends critically on the percentage of the planetary land/ocean coverage (Franck et al. 2003) and is significantly increased for planets with a high percentage of ocean surface (water worlds).
Cuntz, M., von Bloh, W., Bounama, C., and Franck, S. 2003. Icarus 162, 214.
Franck, S., Cuntz, M., von Bloh, W., and Bounama, C. 2003. Int. J. Astrobiology 2(1), 35.
Von Bloh, W., Cuntz, M., Franck, S., and Bounama, C. 2003. Astrobiology 3(4), 681.
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Bulletin of the American Astronomical Society, 36 #2
© 2004. The American Astronomical Soceity.