Tuesday, February 14, 2017
The number of known transiting exoplanets has increased manyfold in the years since Kepler was launched, mainly thanks to the abundant harvest from the mission itself. Statistical analyses of the planets discovered by Kepler and K2 indicate that planets with sizes between 1 and 4 Earth radii are more common than larger ones in our galaxy. These planets can theoretically have a wide range of compositions which we are just beginning to explore observationally. Meaningful constraints on their atmospheres, masses and radii - and thus their density and composition - are generally feasible only for those planets that transit bright, nearby stars. I will present the small ensemble of known sub-Neptune exoplanets that are amenable to mass measurements or atmospheric characterization. I will discuss what we have learned about these systems so far, and how they inform our current understanding of this population of exoplanets. I will conclude by describing how TESS will revolutionize this understanding by significantly increasing the number of known small exoplanets with bright host stars, and by enabling the exploration of trends between their density, composition, orbital parameters and the properties of the host star.