# Optical Properties of Organic Hazes in Water-rich Exoplanet Atmospheres: Implications for Observations with JWST

**Authors:** Chao He, Michael Radke, Sarah E. Moran, Sarah M. Horst, Nikole K. Lewis, Julianne I. Moses, Mark S. Marley, Natasha E. Batalha, Eliza M. -R. Kempton, Caroline V. Morley, Jeff A. Valenti, Veronique Vuitton  
**arXiv:** [2301.02745](https://arxiv.org/abs/2301.02745)  
**Date:** 2023-01-06  
**Summary page:** https://www.summarizepaper.com/en/paper/2301.02745v1/

## Key points

- The James Webb Space Telescope (JWST) has started its scientific mission, including the atmospheric characterization of transiting exoplanets.
- Some of the first observed exoplanets have equilibrium temperatures below 1000 K, where photochemical hazes are expected to form.
- Researchers generated organic haze analogues in water-rich exoplanet atmosphere experiments and measured their optical properties across a wide range of wavelengths.
- Using these optical constants, hazy model atmospheric spectra were generated and differences in haze optical constants were found to have a detectable effect on the spectra.
- Transit depth differences between haze models range from ~100 ppm in the mid-IR to ~150 ppm in the visible and near-IR—all within the sensitivity of JWST and Hubble measurements.
- This study highlights the need for further investigation into how different haze optical properties impact our interpretation of exoplanet observations and establishes a practical procedure to determine such properties.
- Simplified assumptions were used in this simulation, and future model development is required for a comprehensive exploration into haze impacts on observations of exoplanet atmospheres.

## Summary

The James Webb Space Telescope (JWST) has recently begun its scientific mission, which includes the atmospheric characterization of transiting exoplanets. Some of the first exoplanets observed by JWST have equilibrium temperatures below 1000 K, where photochemical hazes are expected to form. To address this gap in knowledge, a team of researchers generated organic haze analogues in water-rich exoplanet atmosphere experiments and measured their optical properties (0.4 to 28.6 micron). The resulting data cover the entire wavelength range of JWST instrumentation and a large part of Hubble. Using these optical constants, the researchers generated hazy model atmospheric spectra and found that differences in haze optical constants have a detectable effect on the spectra. The transit depth differences between haze models range from ~100 ppm in the mid-IR to ~150 ppm in the visible and near-IR—all of which are well within the sensitivity of JWST and Hubble measurements. This study emphasizes the need for further investigation into how different haze optical properties impact our interpretation of exoplanet observations and establishes a practical procedure to determine such properties. Simplified assumptions were used in this simulation—such as atmospheric pressure-temperature profiles and particle radius and mass distribution—and future model development is required for a comprehensive exploration into haze impacts on observations of exoplanet atmospheres.