Hazy Views of Nearby Worlds: Standing Between Two Eras of Exoplanet Characterization

We currently stand at a threshold: between the Kepler and TESS missions, we have nearly completed our inventory of nearby transiting planets in our neighborhood. The Hubble and Spitzer space telescopes, as well as dedicated ground-based efforts, have provided a taste of the diversity of their atmospheres. The largest and hottest have atmospheres like stars, with metals and ions. Many have atmospheres that, like those in the solar system, are filled with clouds and hazes, often obscuring our views. Some of the smallest, rocky planets we have observed, the size of the Earth, may retain atmospheres, but at least some appear to have lost their atmospheres during their lifetimes. Armed with these hints (and our increasingly complete census of nearby planets), exoplanet astronomers are chomping at the bit for the next step, which will be facilitated by the launch of the James Webb Space Telescope: to characterize in detail the atmospheres of our neighbors, large and small. I will discuss both our current picture of exoplanet science, and touch on the types of programs that can be done with JWST that will progress our knowledge of planetary physics the most. I will discuss what the prospects are for gas giants, including those much colder than any discovered to date; for sub-Neptunes, between Earth and Neptune in size, for which no solar systeman alogs exist, but which are among the most numerous planets; and finally, I will discuss our prospects for observing Earths (both hot and “habitable”).