Do Photochemical Hazes Cloud the Atmosphere of 51 Eri b?
Abstract
The first young giant planet to be discovered by the Gemini Planet Imager was the ~ 2MJ planet 51 Eri b. This ~20 Myr old young Jupiter is the first directly imaged planet to show unmistakable methane in H band. To constrain the planet’s mass, atmospheric temperature, and composition, the GPI J and H band spectra as well as some limited photometric points were compared to the predictions of substellar atmosphere models. The best fitting models reported in the discovery paper (Macintosh et al. 2015) relied upon a combination of clear and cloudy atmospheric columns to reproduce the data. In the atmosphere of an object as cool as 700 K the global silicate and iron clouds would be expected to be found well below the photosphere, although strong vertical mixing in the low gravity atmosphere is a possibility. Instead, clouds of Na2S, as have been detected in brown dwarf atmospheres, are a likely source of particle opacity. As a third explanation we have explored whether atmospheric photochemistry, driven by the UV flux from the primary star, may yield hazes that also influence the observed spectrum of the planet. To explore this possibility we have modeled the atmospheric photochemistry of 51 Eri b using two state-of-the-art photochemical models, both capable of predicting yields of complex hydrocarbons under various atmospheric conditions. We also have explored whether photochemical products can alter the equilibrium temperature profile of the atmosphere. In our presentation we will summarize the modeling approach employed to characterize 51 Eri b, explaining constraints on the planet’s effective temperature, gravity, and atmospheric composition and also present results of our studies of atmospheric photochemistry. We will discuss whether photochemical hazes could indeed be responsible for the particulate opacity that apparently sculpts the spectrum of the planet.
- Publication:
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AAS/Division for Extreme Solar Systems Abstracts
- Pub Date:
- December 2015
- Bibcode:
- 2015ESS.....320203M