Probing exoplanet atmospheres with Raman scattering (speaker: Antonija Oklopčić, CalTech)

Monday, September 19, 12:00pm

Abstract: Rayleigh scattering is an important source of opacity in the atmospheres of exoplanets at short optical and near-UV wavelengths. Raman scattering on molecules is an inelastic process related to Rayleigh scattering which leaves specific spectral signatures imprinted in the reflected light and the geometric albedo spectrum of the planet. These spectral features can be used to probe the atmospheres of exoplanets. The intensity of Raman features depends on the column of the atmosphere that the radiation passes through before being scattered into our line of sight and hence can provide information on the presence and altitude of clouds, even in atmospheres composed of heavy molecular species. The so-called Raman ghost lines could be used to spectroscopically identify the main scatterer in the atmosphere, even molecules like hydrogen or nitrogen, which do not show prominent spectral signatures in the optical wavelength range. If detected, these ghost lines could also provide information about the temperature of the atmosphere. In this talk I will present a feasibility analysis for detecting Raman spectral features in nearby exoplanets using the next-generation observational facilities. I will also discuss which stellar types are the most promising candidates for hosting exoplanets with strong Raman features in their albedo spectra.