Striking Exoplanetary Gold: Systems with Multiple Transiting Planets from the Kepler Space Telescope

Our generation is the first to characterize planets around other stars ("exoplanets") well enough to determine their densities, a crucial step towards understanding exoplanet formation and habitability. Measuring densities requires determining the mass and size of an exoplanet. Exoplanetary radii are measured by observing the amount of light lost as a planet passes in front of ("transits") its parent star. Exoplanetary masses are determined by observing the gravitational effect of a planet on the star or on other planets. As planet-planet interactions are larger, it is sometimes easier to measure masses (and thus densities) by watching for gravitational interactions between the planets. One of the greatest discoveries of NASA's Kepler Space Telescope (“Kepler”) is the identification of stars with multiple transiting exoplanets because it enables density measurements of small exoplanets. Kepler has discovered about 700 systems with multiple transiting planets, a huge milestone for exoplanet discovery. After describing these systems, their value, and what we already know, I will discuss a new method that I will apply to provide the most precise and accurate densities for the largest number of Kepler exoplanets.