Presentation #320.08 in the session Exoplanets Transits I.
Many processes in planet evolution happen during the first few million years after disk dispersal. However, nearly all known exoplanets are billions of years old. I will discuss how new data from Gaia and TESS are helping to rectify this situation, by enabling the discoveries of the youngest planets from the prime Kepler mission. These planets come from a dispersed group of 38 ± 6 million year old stars spanning Cepheus (l=100°) to Hercules (l=45°), hereafter the Cep-Her complex. This group includes four previously known Kepler Objects of Interest: Kepler-1627 Ab (3.8 ± 0.1 Earth radii; 7.2 day orbital period), Kepler-1643 b (2.3 ± 0.2 Earth radii; 5.3 days), KOI-7368 b (2.2 ± 0.1 Earth radii, 6.8 days), and KOI-7913 Ab (2.3 ± 0.2 Earth radii, 24.2 days). The color-absolute magnitude diagrams from Gaia, all-sky stellar rotation periods from TESS, and spectroscopy show that these systems are all between 35 and 50 million years old. Based on the transit shapes and high resolution imaging, we also statistically validate them as planets (FPP < 1%). With help from Gaia and TESS, the main Kepler mission is at last expanding the census of young close-in planets, and is yielding the first empirical demonstration that mini-Neptunes with sizes of ≈2 Earth radii exist at ages of ≈40 million years.