Optical Properties of Organic Haze Analogues in Water-rich Exoplanet Atmospheres Observable with JWST

TL;DR

This study measures the optical properties of organic haze analogues in water-rich exoplanet atmospheres to improve interpretation of JWST observations, highlighting the impact of haze properties on spectral analysis.

Contribution

It provides the first comprehensive optical constants for organic haze analogues across JWST's wavelength range, aiding atmospheric modeling and interpretation.

Findings

Optical constants cover 0.4 to 28.6 μm for haze analogues.

Haze optical properties significantly affect synthetic spectra.

The study offers a procedure to determine haze optical properties.

Abstract

JWST has begun its scientific mission, which includes the atmospheric characterization of transiting exoplanets. Some of the first exoplanets to be observed by JWST have equilibrium temperatures below 1000 K, which is a regime where photochemical hazes are expected to form. The optical properties of these hazes, which controls how they interact with light, are critical for interpreting exoplanet observations, but relevant experimental data are not available. Here we measure the density and optical properties of organic haze analogues generated in water-rich exoplanet atmosphere experiments. We report optical constants (0.4 to 28.6 {\mu}m) of organic haze analogues for current and future observational and modeling efforts covering the entire wavelength range of JWST instrumentation and a large part of Hubble. We use these optical constants to generate hazy model atmospheric spectra. The synthetic spectra show that differences in haze optical constants have a detectable effect on the spectra, impacting our interpretation of exoplanet observations. This study emphasizes the need to investigate the optical properties of hazes formed in different exoplanet atmospheres, and establishes a practical procedure to determine such properties.