Query : 2020A&A...640A.121G

2020A&A...640A.121G - Astronomy and Astrophysics, volume 640A, 121-121 (2020/8-1)

Colors of an Earth-like exoplanet. Temporal flux and polarization signals of the Earth.


Abstract (from CDS):

Context. Understanding the total flux and polarization signals of Earth-like planets and their spectral and temporal variability is essential for the future characterization of such exoplanets.
Aims. We provide computed total (F) and linearly (Q and U) and circularly (V) polarized fluxes, and the degree of polarization P of sunlight that is reflected by a model Earth, to be used for instrument designs, optimizing observational strategies, and/or developing retrieval algorithms.
Methods. We modeled a realistic Earth-like planet using one year of daily Earth-observation data: cloud parameters (distribution, optical thickness, top pressure, and particle effective radius), and surface parameters (distribution, surface type, and albedo). The Stokes vector of the disk-averaged reflected sunlight was computed for phase angles α from 0° to 180°, and for wavelengths λ from 350 to 865nm.
Results. The total flux F is one order of magnitude higher than the polarized flux Q, and Q is two and four orders of magnitude higher than U and V, respectively. Without clouds, the peak-to-peak daily variations due to the planetary rotation increase with increasing λ for F, Q, and P, while they decrease for U and V. Clouds modify but do not completely suppress the variations that are due to rotating surface features. With clouds, the variation in F increases with increasing λ, while in Q, it decreases with increasing λ, except at the largest phase angles. In earlier work, it was shown that with oceans, Q changes color from blue through white to red. The α where the color changes increases with increasing cloud coverage. Here, we show that this unique color change in Q also occurs when the oceans are partly replaced by continents, with or without clouds. The degree of polarization P shows a similar color change. Our computed fluxes and degree of polarization will be made publicly available.

Abstract Copyright: © ESO 2020

Journal keyword(s): radiative transfer - polarization - techniques: polarimetric - planets and satellites: terrestrial planets - planets and satellites: atmospheres - planets and satellites: surfaces

Simbad objects: 4

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Number of rows : 4
N Identifier Otype ICRS (J2000)
ICRS (J2000)
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2023
1 TOI-700 PM* 06 28 23.2285331376 -65 34 45.520447908   14.524 13.076 12.659 10.70 M2V 41 0
2 TOI-700b Pl 06 28 23.2287828000 -65 34 45.521569925           ~ 9 0
3 NAME Luhman 16A BD* 10 49 14.0238534572 -53 19 05.005159625           L7.5 48 0
4 * 51 Peg b Pl 22 57 27.9804167474 +20 46 07.782240714           ~ 646 1

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