Extrasolar Planet Orbits and Eccentricities

The known extrasolar planets exhibit many interesting and surprising features—extremely short‐period orbits, high‐eccentricity orbits, mean‐motion and secular resonances, etc.—and have dramatically expanded our appreciation of the diversity of possible planetary systems. In this review we summarize the orbital properties of extrasolar planets. One of the most remarkable features of extrasolar planets is their high eccentricities, far larger than seen in the solar system. We review theoretical explanations for large eccentricities and point out the successes and shortcomings of existing theories.