The Global Climates, Clouds, and Dynamics of the Hottest Jupiters
Abstract
The atmospheres of ultra-hot Jupiters (>3000K) exist in an extreme state of day-night disequilibrium, giving us one of the best opportunities to study the dynamic processes in giant planet atmospheres. By using orbital phase curve observations of these planets we can construct a global map of their thermal emission, and watch their atmospheres change as gas moves from day to night and back again. Besides providing us with a better understanding of hot Jupiter atmospheres, this also allows us to study what would otherwise be observationally inaccessible atmospheric processes. Specifically, we can see the formation of clouds near planetary dusk, their destruction shortly after dawn, and use this to constrain the physics of cloud formation and dissolution in both exoplanets and brown dwarfs. We can also use phase curve observations of extremely hot, cloudless, planets to directly trace the underlying dynamics and mixing in these atmospheres.
We will illustrate this using new results from our new HST/WFC3 phase curves of KELT-1b and new dual-band Spitzer phase curves of KELT-9b. For KELT-1b, our spectroscopic phase curves of KELT-1b show — for the first time — the broadband and spectroscopic signatures of the formation and break-up of these nightside clouds. Coupled with previous broadband Spitzer phase curve observations, this gives us new insight into the cloud formation timescales and cloud compositions on hot Jupiters. We will also present new 3.6um and 4.5um Spitzer phase curves of KELT-9b, which, at 4600K, is the hottest giant planet known. Unlike all other hot Jupiters, KELT-9b shows a strongly non-sinosoidal phase curve in both Spitzer bands. Also unlike all other hot Jupiters, the extreme temperature of KELT-9b's atmosphere means that it is completely cloudless, and we will discuss how the phase curve variation we see is driven by atmospheric dynamics. The high temperature also causes molecular hydrogen to dissociate on the dayside, and by using the strong opacity difference between H and H2 in the two IRAC channels, we can use the hydrogen dissociation / recombination reaction as a direct tracer of the atmospheric gas dynamics.- Publication:
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AAS/Division for Extreme Solar Systems Abstracts
- Pub Date:
- August 2019
- Bibcode:
- 2019ESS.....450005B