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DIX Planetary Science Seminar

Tuesday, December 1, 2020
4:00pm to 5:00pm
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Online Event
Atmospheric Mixing in Cool Exoplanet Analogs
Brittany Miles, Graduate Reserach Fellow, Astronomy & Astrophysics, UC Santa Cruz,

Abstract: Cold brown dwarfs are excellent analogs of widely separated, gas giant exoplanets, and provide insight into the potential atmospheric chemistry and physics we may encounter in objects to be discovered by future direct imaging surveys. Disequilibrium chemistry driven by atmospheric mixing is common among brown dwarfs, and by extension we expect to see a similar or increased effect on gas giant exoplanets. I will provide background on disequilibrium chemistry and previous efforts to characterize it in warmer (>1000 K) brown dwarfs and Solar System gas giants. I'll then present the results from Miles+2020, a low-resolution, R ∼ 300, M-band spectroscopic sequence of seven brown dwarfs with effective temperatures between 750 K and 250 K along with Jupiter. These spectra reveal disequilibrium abundances of carbon monoxide (CO) produced by atmospheric mixing. The eddy diffusion coefficient (Kzz) is used to estimate the strength of vertical atmospheric mixing in each object. The Kzz values of cooler gaseous objects are close to their theoretical maximum, and warmer objects show weaker mixing, likely due to less efficient convective mixing in primarily radiative layers.

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