1110.4525 (M Joshi et al.)
M Joshi, R Haberle
M-stars comprise 80% of main-sequence stars, and so their planetary systems
provide the best chance for finding habitable planets, i.e.: those with surface
liquid water. We have modelled the broadband albedo or reflectivity of water
ice and snow for simulated planetary surfaces orbiting two observed red dwarf
stars (or M-stars) using spectrally resolved data of the Earth's cryosphere.
The gradual reduction of the albedos of snow and ice at wavelengths greater
than 1 ?m, combined with M-stars emitting a significant fraction of their
radiation at these same longer wavelengths, mean that the albedos of ice and
snow on planets orbiting M-stars are much lower than their values on Earth. Our
results imply that the ice/snow albedo climate feedback is significantly weaker
for planets orbiting M-stars than for planets orbiting G-type stars such as the
Sun. In addition, planets with significant ice and snow cover will have
significantly higher surface temperatures for a given stellar flux if the
spectral variation of cryospheric albedo is considered, which in turn implies
that the outer edge of the habitable zone around M-stars may be 10-30% further
away from the parent star than previously thought.
View original:
http://arxiv.org/abs/1110.4525
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