N. Madhusudhan (Yale University, Physics and Astronomy, New Haven, CT, United States),
H. Knutson (California Institute of Technology, Geological and Planetary Sciences, United States),
J. Fortney (University of California - Santa Cruz, Astronomy and Astrophysics, United States),
T. Barman (Lowell Observatory, United States)
The study of exoplanetary atmospheres is one of the most exciting and dynamic frontiers in astronomy.
Over the past two decades ongoing surveys have revealed an astonishing diversity in the planetary
masses, radii, temperatures, orbital parameters, and host stellar properties of exoplanetary systems.
We are now moving into an era where we can begin to address fundamental questions concerning the
diversity of exoplanetary compositions, atmospheric and interior processes, and formation histories,
just as have been pursued for solar system planets over the past century. Exoplanetary atmospheres
provide a direct means to address these questions via their observable spectral signatures. In the last
decade, and particularly in the last five years, tremendous progress has been made in detecting atmospheric
signatures of exoplanets through photometric and spectroscopic methods using a variety of
space-borne and/or ground-based observational facilities. These observations are beginning to provide
important constraints on a wide gamut of atmospheric properties, including pressure-temperature profiles,
chemical compositions, energy circulation, presence of clouds, and non-equilibrium processes.
The latest studies are also beginning to connect the inferred chemical compositions to exoplanetary
formation conditions. In the present chapter, we review the most recent developments in the area
of exoplanetary atmospheres. Our review covers advancements in both observations and theory of
exoplanetary atmospheres, and spans a broad range of exoplanet types (gas giants, ice giants, and
super-Earths) and detection methods (transiting planets, direct imaging, and radial velocity). A number
of upcoming planet-finding surveys will focus on detecting exoplanets orbiting nearby bright stars,
which are the best targets for detailed atmospheric characterization. We close with a discussion of the
bright prospects for future studies of exoplanetary atmospheres.
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