期刊
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
卷 113, 期 41, 页码 11431-11435出版社
NATL ACAD SCIENCES
DOI: 10.1073/pnas.1604692113
关键词
orbital eccentricities; exoplanets; transit; solar system; planetary dynamics
资金
- Key Development Program of Basic Research of China (973 Program) [2013CB834900]
- National Natural Science Foundation of China (NSFC) [11333002]
- Foundation for the Author of National Excellent Doctoral Dissertation of People's Republic of China
- Strategic Priority Research Program, The Emergence of Cosmological Structures of the Chinese Academy of Sciences [XDB09000000]
- NSFC [11573003, U1231202, 11403056, 11403012, 11503009, 11673011]
- Center for Astronomical Mega-Science, Chinese Academy of Sciences
- Chinese Academy of Sciences [U1231202]
- National Basic Research Program of China (973 Program) [2013CB834900, 2014CB845700]
- National Development and Reform Commission
- Direct For Mathematical & Physical Scien
- Division Of Astronomical Sciences [1409421] Funding Source: National Science Foundation
The nearly circular (mean eccentricity (e) over bar approximate to 0.06) and coplanar (mean mutual inclination (i) over bar approximate to 3 degrees) orbits of the solar system planets motivated Kant and Laplace to hypothesize that planets are formed in disks, which has developed into the widely accepted theory of planet formation. The first several hundred extrasolar planets (mostly Jovian) discovered using the radial velocity (RV) technique are commonly on eccentric orbits ((e) over bar approximate to 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 Large Sky Area Multi-Object Fiber Spectroscopic Telescope (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), whereas the other half are multiple transiting planets (multiples). We find an eccentricity dichotomy: on average, Kepler singles are on eccentric orbits with (e) over bar approximate to 0.3, whereas the multiples are on nearly circular ((e) over bar = 0.04(-0.04)(+0.03)) and coplanar ((i) over bar = 1.4(-1.1)(+0.8) degree) orbits similar to those of 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) over bar approximate to (1-2) x (i) over bar] 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.
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