“Planetary Systems through Time”

Planets are not born in their final state. Young planets are sculpted by interactions with their host star, other planets in the system, and their greater environment. Large populations of mature (>1 Gyr) exoplanets, like those from the Kepler mission, provide useful but indirect constraints on the relative importance of such evolutionary processes. Because the first few hundred million years of a planet's life are the most formative, studies of young (<1 Gyr) planets yield more direct information on exoplanet evolution, providing an opportunity to observe such processes in action. Identifying and characterizing young planets poses significant challenges, but the advent of K2 and TESS data, coupled with new planet-search methods, has enabled the discovery of dozens of transiting planets in 2–700 Myr clusters, moving groups, and star-forming regions. The statistical properties of these systems reveal that young planets are larger than their older counterparts and offer insights into the timescales of planetary migration. Furthermore, with the aid of transmission spectroscopy from JWST, we have our first glimpses into the atmospheres of these infant planets, which have already provided a wealth of information regarding the structure and composition of a subset of the youngest planets.