Characterization of the Atmosphere of Extrasolar Planets

Abstract

Context: Starting from the first discovery of extrasolar planet or exoplanet around a sun-like star, more than 5,000 confirmed exoplanets have been detected till now. But still we have very less information and interpretations about the atmosphere of such outside worlds. Aim: In this project we mainly focus on gas-giant exoplanets, commonly known as hot-jupiters due to their jupiter-like shape and structure but a huge tempera ture. We studied the atmosphere in two different aspects. At first we modeled the day-side emission spectra and studied their variation with respect to different amount of atmospheric flow and heat-redistribution using the existing radiative transfer theory. Then we modified the current theory of diffuse reflection prob lem according to the context of Hot-Jupiter atmospheric temperature structure to provide more accurate interpretations of present and future data. Methodology: For the first part of the work we used numerical simulation and analytical approach to study the atmospheric redistribution effect. In the numer ical context the discrete space theory formalism is used for the first time to solve the line-by-line radiative transfer equation and generates the planetary emission spectra. In the second part of the project, a purely analytical approach is taken to modify the existing theory of diffuse reflection problem by adding the atmo spheric thermal emission contribution to it. The Invariance principle method is used for this modification treatment. Results: In the first part of this work we have showed that the atmospheric heat redistribution plays a major role in changing the vertical atmospheric temperature pressure structure as well as the day-side emission spectra. Depending on the amount of (full, semi and no) heat redistribution the magnitude of the day-side emission flux changes substantially. We also considered a particular case of hot jupiter XO-1b and showed that this planet has efficient day-night heat redistribu tion and holds the same temperature structure all over the planet. In the second project we showed that the modified results of diffuse reflection problem incor porates both the effects of thermal emission and diffuse reflection in the final ra diation from the planetary atmosphere. Also our results in this context is more general and consistent with the previous results as obtained by Chandrasekhar in i case of only scattering. Hence we conclude that our approach will provide more accurate and reliable interpretations of the data observed in exoplanetary science.