3407 20180116111913.0 10.1073/pnas.1604692113 DOI SCART-2018-0020 Xie, J.-W. Exoplanet orbital eccentricities derived from LAMOST-Kepler analysis 2016 The nearly circular (mean eccentricity <e>~0.06) and coplanar (mean mutual inclination <i>~3 deg) orbits of the Solar System planets motivated Kant and Laplace to put forth the hypothesis that planets are formed in disks, which has developed into the widely accepted theory of planet formation. Surprisingly, the first several hundred extrasolar planets (mostly Jovian) discovered using the Radial Velocity (RV) technique are commonly on eccentric orbits (<e> ~ 0.3). This raises a fundamental question: Are the Solar System and its formation special? The Kepler mission has found thousands of transiting planets dominated by sub-Neptunes, but most of their orbital eccentricities remain unknown. By using the precise spectroscopic host star parameters from the LAMOST observations, we measure the eccentricity distributions for a large (698) and homogeneous Kepler planet sample with transit duration statistics. Nearly half of the planets are in systems with single transiting planets (singles), while the other half are multiple-transiting planets (multiples). We find an eccentricity dichotomy: on average, Kepler singles are on eccentric orbits with <e>~0.3, while the multiples are on nearly circular (<e> = 0.04^{+0.03}_{-0.04}) and coplanar (<i> = 1.4^{+0.8}_{-1.1} deg) orbits similar to the Solar System planets. Our results are consistent with previous studies of smaller samples and individual systems. We also show that Kepler multiples and solar system objects follow a common relation <e>~(1-2)x<i> between mean eccentricities and mutual inclinations. The prevalence of circular orbits and the common relation may imply that the solar system is not so atypical in the galaxy after all. NO orbital eccentricities exoplanets transit solar system planetary dynamics Dong, S. Zhu, Z.H. Huber, D. Zheng, Z De Cat, P. Fu, J.N. Liu, H.-G. Luo, A. Wu, Y. Zhang, H.T. Zhang, H. Zhou, J.-L. Cao, Z.H. Hou, Y.H. Wang, Y.F. Zhang, Y. Proceedings of the National Academy of Sciences 113 2016 41 11431-11435 peter@observatoire.be http://www.pnas.org/content/113/41/11431 http://www.pnas.org/content/113/41/11431.full https://arxiv.org/abs/1609.08633 published in REFERD