Exoplanets & Exomoons

Detection of Aerosols at Microbar Pressures in an Exoplanet Atmosphere

By Keith Cowing
June 21, 2021
Filed under
Detection of Aerosols at Microbar Pressures in an Exoplanet Atmosphere
Broadband white light curve of WASP-69b for HST/G430L (green), HST/G750L (yellow), and HST/G414 (blue), and the retrieved transit model is indicated in red.

Formation of hazes at microbar pressures has been explored by theoretical models of exoplanet atmospheres to explain Rayleigh scattering and/or featureless transmission spectra, however observational evidence of aerosols in the low pressure formation environments has proved elusive.

Here, we show direct evidence of aerosols existing at ∼1 microbar pressures in the atmosphere of the warm sub-Saturn WASP-69b using observations taken with Space Telescope Imaging Spectrograph (STIS) and Wide Field Camera 3 (WFC3) instruments on the Hubble Space Telescope. The transmission spectrum shows a wavelength-dependent slope induced by aerosol scattering that covers 11 scale heights of spectral modulation.

Drawing on the extensive studies of haze in our Solar System, we model the transmission spectrum based on a scaled version of Jupiter’s haze density profile to show that WASP-69b transmission spectrum can be produced by scattering from an approximately constant density of particles extending throughout the atmospheric column from 40 millibar to microbar pressures. These results are consistent with theoretical expectations based on microphysics of the aerosol particles that have suggested haze can exist at microbar pressures in exoplanet atmospheres.

Raissa Estrela, Mark Swain, Gael Roudier, Robert West, Elyar Sedaghati, Adriana Valio

Comments: 15 pages, 13 figures, accepted for publication in AJ
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:2106.10292 [astro-ph.EP] (or arXiv:2106.10292v1 [astro-ph.EP] for this version)
Submission history
From: Raissa Estrela
[v1] Fri, 18 Jun 2021 18:00:05 UTC (6,252 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) 🖖🏻