From: LARRY KLAES (ljk4_at_msn.com)
Date: Mon Oct 29 2007 - 20:26:02 PDT
Habitable planets around the star Gl 581?
Authors: Franck Selsis (CRAL, LAB), J. F. Kasting, B. Levrard (CRAL, IMCCE),
J. Paillet, I. Ribas, X. Delfosse (LAOG)
(Submitted on 28 Oct 2007)
Abstract: Radial velocity surveys are now able to detect terrestrial planets
at habitable distance from M-type stars. Recently, two planets with minimum
masses below 10 Earth masses were reported in a triple system around the
M-type star Gliese 581. Using results from atmospheric models and
constraints from the evolution of Venus and Mars, we assess the habitability
of planets Gl 581c and Gl 581d and we discuss the uncertainties affecting
the habitable zone (HZ) boundaries determination. We provide simplified
formulae to estimate the HZ limits that may be used to evaluate the
astrobiological potential of terrestrial exoplanets that will hopefully be
discovered in the near future. Planets Gl 581c and 'd' are near, but
outside, what can be considered as the conservative HZ. Planet 'c' receives
30% more energy from its star than Venus from the Sun, with an increased
radiative forcing caused by the spectral energy distribution of Gl 581. Its
habitability cannot however be positively ruled out by theoretical models
due to uncertainties affecting cloud properties. Irradiation conditions of
planet 'd' are comparable with those of early Mars. Thanks to the warming
effect of CO2-ice clouds planet 'd' might be a better candidate for the
first exoplanet known to be potentially habitable. A mixture of various
greenhouse gases could also maintain habitable conditions on this planet.
Comments: Astronomy and Astrophysics (2007) accepted for publication
Subjects: Astrophysics (astro-ph)
Cite as: arXiv:0710.5294v1 [astro-ph]
Submission history
From: Franck Selsis [view email] [via CCSD proxy]
[v1] Sun, 28 Oct 2007 15:37:38 GMT (389kb)
http://arxiv.org/abs/0710.5294
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