Imaging & Spectroscopy

Optical Properties Of Organic Hazes In Water-rich Exoplanet Atmospheres: Implications For Observations With JWST

By Keith Cowing
Press Release
astro-ph.EP
January 10, 2023
Filed under , , , , ,
Optical Properties Of Organic Hazes In Water-rich Exoplanet Atmospheres: Implications For Observations With JWST
Model spectra of a water-rich atmosphere around a GJ 1214 b -like planet, showing the effect of our newly measured haze optical properties. We also show the existing Hubble data of GJ 1214 b (Kreidberg et al. 2014)1 . All spectra have been normalized by subtracting the mean of each transit depth from the spectrum, to better show the relative sizes of absorption features. The top panel (A) shows the spectra of our modeled atmospheres from 0.4 to 14 microns; bottom panel (B) shows our model atmospheres focused on Hubble Wide Field Camera 3/G141 instrument wavelengths. In teal, we show models of clear atmospheres with the laboratory atmospheric composition. Orange lines show hazy models generated using the optical properties for Titan-like hazes as measured by Khare et al. (1984). Red and blue lines show models generated using our newly derived optical properties for hazes made from 400 and 300 K water-rich atmospheres, respectively. The molecules and/or hazes responsible for the atmospheric features are indicated in each plot. Given the same other atmospheric assumptions, the presence of our newly measured hazes would be differentiable from a Titan-like haze with observations from existing space-based observatories like Hubble and JWST, as with the GJ 1214 b data shown here. — astro-ph.EP

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 data are not available.

Here we measure the optical properties of organic haze analogues generated in water-rich exoplanet atmosphere experiments. We report optical constants (0.4 to 28.6 micron) of organic hazes 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.

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

Comments: 4 figures, 1 Table, Paper under review in Nature Astronomy
Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Instrumentation and Methods for Astrophysics (astro-ph.IM)
Cite as: arXiv:2301.02745 [astro-ph.EP] (or arXiv:2301.02745v1 [astro-ph.EP] for this version)
Submission history
From: Chao He
[v1] Fri, 6 Jan 2023 23:14:19 UTC (3,208 KB)
https://arxiv.org/abs/2301.02745
Astrobiology, Astrochemistry

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