The “Spectral Zoo” of Exoplanet Atmospheres

Abstract

The great abundance of exoplanets and the unexpectedly wide range of their bulk properties create a huge realm of possibilities in exoplanet atmospheres. Opportunities for atmospheric characterization of other worlds abound, as well as pitfalls for the unwary. In this chapter, we make a first foray into exploring the richness of exoplanet atmospheres, with a tour of the exoplanet “spectral zoo.” We then follow the path of light from a star onto an exoplanet and to a distant spectrograph; the details of what happens to that light within the planet’s atmosphere will be discussed in other chapters. We briefly discuss how the light is then affected by the spectrograph and recorded by a detector, resulting in an observed planet spectrum. As will be seen, one of the major challenges for measuring the effects of a planet’s atmosphere in an observed spectrum is disentangling them from effects caused by the instrumentation used to acquire that spectrum. We conclude with a few thoughts on general strategies to overcome observational challenges and harvest the best science from the treasure trove of exoplanets we can and will study in the coming decades.