Uses of Linear Polarization as a Probe of Extrasolar Planet Atmospheres

TL;DR

Linear polarization observations of extrasolar planets can greatly improve contrast with their stars and provide insights into atmospheric properties, making it a promising method for exoplanet characterization.

Contribution

This paper highlights the advantages of using linear polarization measurements to study extrasolar planet atmospheres and discusses the feasibility of such observations.

Findings

LP contrast between stars and planets can be over 10,000 times

LP data can diagnose atmospheric composition, size, and shape

Feasibility of LP observations for exoplanets is promising

Abstract

We point out some advantages of making observations of extrasolar planets in linearly polarized (LP) light. Older cool stars have quite low levels (~ 10^-4 to 10^-5) of fractional LP, while extrasolar planets can have relatively high fractional LP (~0.1). Observations in LP light can therefore significantly enhance contrast between the planet and its parent star. Data on LP as a function of planetary orbital phase can be used to diagnose the properties (e.g., composition, size, and shape) of the scatterers in the planetary atmosphere. We discuss the feasibility of LP observations of extrasolar planets.