Atmospheres & Climate

Feasibility Study on Retrieving Exoplanetary Cloud Cover Distributions Using Polarimetry

By Keith Cowing
Status Report
May 22, 2024
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Feasibility Study on Retrieving Exoplanetary Cloud Cover Distributions Using Polarimetry
Polarization of planetary phase functions for the cases of two cloud cap configurations and for a cloud-free atmosphere to illustrate the effect of locally obscured limb polarization on the net phase function at wavelengths of πœ† = 550 nm. The three panels show the spatially resolved normalized Stokes parameters π‘ž(𝛼) and 𝑒(𝛼) for selected phase angles 𝛼 of spatially resolved planetary disks. — astro-ph.EP

Context. As a new growing field, exocartography aims to map the surface features of exoplanets that are beyond the resolution of traditional observing techniques. While photometric approaches have been discussed extensively, polarimetry has received less attention despite its promising prospects.

Aims. We demonstrate that the limb polarization of an exoplanetary atmosphere offers valuable insights into its cloud cover distribution. Specifically, we determine an upper limit for the polarimetric precision, which is required to extract information about the latitudinal cloud cover of temperate Jovian planets for scenarios of observations with and without host stars.

Methods. To compute the scattered stellar radiation of an exoplanetary atmosphere and to study the polarization at various planetary phase angles, we used the three-dimensional Monte Carlo radiative transfer code POLARIS.

Results. When the planetary signal can be measured separately from the stellar radiation, information about the latitudinal cloud cover for polar cap models is accessible at polarimetric sensitivities of 0.1 %. In contrast, a precision of about 10βˆ’3 ppm is required when the stellar flux is included to gain this information.

S. Winning, M. Lietzow-Sinjen, S. Wolf

Comments: Accepted for publication in Astronomy & Astrophysics. 8 pages, 5 figures
Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Instrumentation and Methods for Astrophysics (astro-ph.IM)
Cite as: arXiv:2405.12727 [astro-ph.EP] (or arXiv:2405.12727v1 [astro-ph.EP] for this version)
Submission history
From: Simon Winning
[v1] Tue, 21 May 2024 12:33:09 UTC (829 KB)


Explorers Club Fellow, ex-NASA Space Station Payload manager/space biologist, Away Teams, Journalist, Lapsed climber, Synaesthete, Na’Vi-Jedi-Freman-Buddhist-mix, ASL, Devon Island and Everest Base Camp veteran, (he/him) πŸ––πŸ»