Atmospheres & Climate

The Infrared Colors Of 51 Eridani b: Micrometereoid Dust Or Chemical Disequilibrium?

By Keith Cowing
Status Report
April 11, 2023
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The Infrared Colors Of 51 Eridani b: Micrometereoid Dust Or Chemical Disequilibrium?
Molecular volume mixing ratios comparing the equilibrium and disequilibrium abundances as a function of pressure altitude. The significant presence of CO in the disequilibrium model is highlighted with a thick curve. Molecules are roughly grouped into color families and labels are constrained to the same y-coordinate in both panels. Additional species noticeably affected by the disequilibrium chemistry include N2, NH3, CO2, and HCN. — astro-ph.EP

We reanalyze near-infrared spectra of the young extrasolar giant planet 51 Eridani b which was originally presented in (Macintosh et al. 2015) and (Rajan et al. 2017) using modern atmospheric models which include a self-consistent treatment of disequilibrium chemistry due to turbulent vertical mixing.

In addition, we investigate the possibility that significant opacity from micrometeors or other impactors in the planet’s atmosphere may be responsible for shaping the observed spectral energy distribution (SED).

We find that disequilibrium chemistry is useful for describing the mid-infrared colors of the planet’s spectra, especially in regards to photometric data at M band around 4.5 μm which is the result of super-equilibrium abundances of carbon monoxide, while the micrometeors are unlikely to play a pivotal role in shaping the SED.

The best-fitting, micrometeroid-dust-free, disequilibrium chemistry, patchy cloud model has the following parameters: effective temperature Teff=681 K with clouds (or without clouds, i.e. the grid temperature Tgrid = 900 K), surface gravity g = 1000 m/s2, sedimentation efficiency fsed = 10, vertical eddy diffusion coefficient Kzz = 103 cm2/s, cloud hole fraction fhole = 0.2, and planet radius Rplanet = 1.0 RJup.

Alexander Madurowicz, Sagnick Mukherjee, Natasha Batalha, Bruce Macintosh, Mark Marley, Theodora Karalidi

Comments: 22 pages, 14 figures, Accepted to AJ
Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Instrumentation and Methods for Astrophysics (astro-ph.IM)
Cite as: arXiv:2304.03850 [astro-ph.EP] (or arXiv:2304.03850v1 [astro-ph.EP] for this version)
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Submission history
From: Alexander Madurowicz
[v1] Fri, 7 Apr 2023 22:15:53 UTC (3,070 KB)
Astrobiology, Astrochemistry,

SpaceRef co-founder, Explorers Club Fellow, ex-NASA, Away Teams, Journalist, Space & Astrobiology, Lapsed climber.