Volume 482, Number 3, May II 2008
|Page(s)||989 - 1007|
|Section||Planets and planetary systems|
|Published online||04 March 2008|
Spectropolarimetric signatures of Earth-like extrasolar planets*
Aerospace Engineering Department, Technical University Delft, Kluyverweg 1, 2629 HS, Delft, The Netherlands
2 SRON Netherlands Institute for Space Research, Sorbonnelaan 2, 3584 CA Utrecht, The Netherlands e-mail: email@example.com
Accepted: 29 December 2007
We present results of numerical simulations of flux F and degree of polarization P of light that is reflected by Earth–like extrasolar planets orbiting solar type stars. Our results are presented as functions of the wavelength (from 0.3 to 1.0 μm, with 0.001 μm spectral resolution) and as functions of the planetary phase angle. We use different surface coverages for our model planets, including vegetation and a Fresnel reflecting ocean, and clear and cloudy atmospheres. Our adding-doubling radiative transfer algorithm, which fully includes multiple scattering and polarization, only handles horizontally homogeneous planets, so we simulate fluxes and polarization of horizontally inhomogeneous planets by weighting results obtained for homogeneous planets. Like F, P of the reflected starlight is shown to depend strongly on the phase angle, on the composition and structure of the planetary atmosphere, on the reflective properties of the underlying surface, and on the wavelength, in particular in wavelength regions with gaseous absorption bands. The sensitivity of P to a planet's physical properties appears to be different than that of F. Combining flux with polarization observations thus makes for a strong tool for characterizing extrasolar planets. The calculated total and polarized fluxes are made available through the CDS.
Key words: polarization / techniques: polarimetric / stars: planetary systems / radiative transfer / Earth
© ESO, 2008
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