The Very Compact Five Exoplanet System KOI-500: Mass Constraints from TTVs, Resonances, and Implications

NASA's Kepler Mission has discovered thousands of planet candidates, including nearly 900 in systems with multiple transiting planet candidates. Such multi-transiting systems are extremely valuable for understanding the combined physical and orbital characteristics of planetary systems. Most of these candidates are in Systems with Tightly-packed Inner Planets (STIPs), which are characterized by a concentration of dynamically tight planets near 0.1 AU. There are about 10 Kepler systems that show 5 or more planets transiting, though it is not yet fully clear whether these are unusual or just a high multiplicity tail of a continuous distribution of STIPs. The first known 5-candidate system was KOI-500 and we here present results which confirm and/or validate all 5 planets and discuss its several distinct properties. Even for a STIP, KOI-500 has a very compact architecture, with all 5 planets within 0.1 AU. The estimated radii of the 1.0, 3.1, 4.6, 7.1, and 9.5-day period planets are 1.3, 1.4, 1.5, 2.4, and 2.6 Earth radii, respectively. The outer four planets are very near unique and interlocking three-body resonances. The outer planets also show Transit Timing Variations (TTVs), allowing for good mass constraints and helping to fill in the exciting small planet mass-radius relation. The inclinations of the planets are generally well constrained, which, in combination with TTVs, allow for an investigation into the true mutual inclinations of this system. We will present an overview of the results of our analysis of the KOI-500 system and place it in context of other STIPs discovered by Kepler and Doppler surveys.