New Diagnostics of Exoplanet Atmospheres: Raman scattering

Antonija Oklopcic (Caltech)

January 30, 2017

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Abstract: Obtaining information about exoplanets” chemical composition and the physical conditions in their atmospheres is crucial for improving our understanding of the physical processes that drive planetary formation and evolution. In order to provide more robust and reliable constraints on the properties of exoplanets, we need to keep searching for new diagnostics of exoplanet atmospheres, complementary to the currently existing methods. In my talk, I will present how spectral signatures of Raman scattering at short optical wavelengths can be used to probe the atmospheres of exoplanets. Raman scattering on molecules in a planetary atmosphere imprints specific features in the geometric albedo spectrum of the planet that can be used to constrain the properties of the atmosphere. The intensity of Raman features is related to the depth of the atmosphere, and can therefore be used to distinguish a clear, deep atmosphere from an atmosphere with high-altitude clouds. Raman features can also be used to spectroscopically identify the main scatterer in the atmosphere, even molecules like hydrogen or nitrogen, which otherwise do not show prominent spectral signatures. The relative intensity of different Raman features depends on the initial population of different molecular levels, and can therefore be used to infer the temperature of the atmosphere. I will discuss the prospects for detecting spectral features of Raman scattering in nearby exoplanets using the next-generation observational facilities. At the end of the talk, I will briefly discuss two other projects — an ongoing work on escaping exoplanet atmospheres and my recent paper on the FIRE simulations of clumpy galaxies at high redshift.