The Clear Sky Corridor: Insights Towards Aerosol Formation in Exoplanets Using An AI-based Survey of Exoplanet Atmospheres

Producing optimized and accurate transmission spectra of exoplanets from telescope data has traditionally been a manual and labor-intensive procedure.

Here we present the results of the first attempt to improve and standardize this procedure using artificial intelligence (AI) based processing of light curves and spectroscopic data from transiting exoplanets observed with the Hubble Space Telescope’s (HST) Wide Field Camera 3 (WFC3) instrument.

We implement an AI-based parameter optimizer that autonomously operates the Eureka pipeline to produce homogeneous transmission spectra of publicly available HST WFC3 datasets, spanning exoplanet types from hot Jupiters to sub-Neptunes. Surveying 43 exoplanets with temperatures between 280 and 2580 Kelvin, we confirm modeled relationships between the amplitude of the water band at 1.4um in hot Jupiters and their equilibrium temperatures.

We also identify a similar, novel trend in Neptune/sub-Neptune atmospheres, but shifted to cooler temperatures. Excitingly, a planet mass versus equilibrium temperature diagram reveals a “Clear Sky Corridor,” where planets between 700 and 1700 Kelvin (depending on the mass) show stronger 1.4um H₂O band measurements. This novel trend points to metallicity as a potentially important driver of aerosol formation. As we unveil and include these new discoveries into our understanding of aerosol formation, we enter a thrilling future for the study of exoplanet atmospheres.

With HST sculpting this foundational understanding for aerosol formation in various exoplanet types, ranging from Jupiters to sub-Neptunes, we present a compelling platform for the James Webb Space Telescope (JWST) to discover similar atmospheric trends for more planets across a broader wavelength range.

Top – An illustration of how each individual is ”sequenced” with an assortment of variable-value pairs relative to transit processing. Bottom – The process for how optimization via parametric sweeps and genetic algorithms operate. While parametric sweeps only optimize to local minima, their optimization is very repeatable, and thus are preferred to genetic optimizers for this application. — astro-ph.EP

Aerosol-formation trends observed between regimes of Jovian and sub-Neptune class exoplanets. Top – Jovian and sub-Neptunes analyzed in this and previous works, compared against notable published models for Jovianaerosol-formation (Gao et al. 2020). Bottom – Jovian and sub-Neptunes analyzed in this and previous works. Jovian exoplanets are shown above the dotted boundary region (∼ 0.1 − 0.13 M_J ), and sub-Neptunes are shown below. A novel, separate pattern for H₂O aerosol formation among the sub-Neptune regime is clear. Furthermore, a newly-found corridor yielding a prominent increase in measured water-band amplitudes is evident. This region presents favorable, clear sky conditions towards identifying atmospheric chemical species across exoplanet regimes, and is defined by a yellow-shaded region. The condensation point for forsterite (Mg₂SiO₄) and aluminum oxide (Al₂O₃), located at ∼ 2100 K, causes the anomalous decrease in water abundance observed in some of the hot Jupiters (Gao et al. 2020). — astro-ph.EP

Reza Ashtari, Kevin B. Stevenson, David Sing, Mercedes Lopez-Morales, Munazza K. Alam, Nikolay K. Nikolov, Thomas M. Evans-Soma

Comments: Accepted to AJ. 14 pages, 5 figures, 3 tables
Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Instrumentation and Methods for Astrophysics (astro-ph.IM); Machine Learning (cs.LG)
Cite as: arXiv:2410.06804 [astro-ph.EP] (or arXiv:2410.06804v1 [astro-ph.EP] for this version)
https://doi.org/10.48550/arXiv.2410.06804
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Submission history
From: Reza Ashtari
[v1] Wed, 9 Oct 2024 12:00:56 UTC (7,614 KB)
https://arxiv.org/abs/2410.06804

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