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A 1.9 Earth Radius Rocky Planet and the Discovery of a Non-transiting Planet in the Kepler-20 System

Buchhave, Lars A. and Dressing, Courtney D. (2016) A 1.9 Earth Radius Rocky Planet and the Discovery of a Non-transiting Planet in the Kepler-20 System. Astronomical Journal, 152 (6). Art. No. 160. ISSN 0004-6256. doi:10.3847/0004-6256/152/6/160.

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Kepler-20 is a solar-type star (V = 12.5) hosting a compact system of five transiting planets, all packed within the orbital distance of Mercury in our own solar system. A transition from rocky to gaseous planets with a planetary transition radius of ~1.6 R⊕ has recently been proposed by several articles in the literature. Kepler-20b (R_p ~ 1.9 R⊕) has a size beyond this transition radius; however, previous mass measurements were not sufficiently precise to allow definite conclusions to be drawn regarding its composition. We present new mass measurements of three of the planets in the Kepler-20 system that are facilitated by 104 radial velocity measurements from the HARPS-N spectrograph and 30 archival Keck/HIRES observations, as well as an updated photometric analysis of the Kepler data and an asteroseismic analysis of the host star (M⋆ = 0.948 ± 0.051 M⊙ and R⋆ = 0.964 ± 0.018 R⊙). Kepler-20b is a 1.868^(+0.066)_(-0.034)R⊕ planet in a 3.7 day period with a mass of 9.70^(+1.41)_(-1.44)M⊕, resulting in a mean density of 8.2^(+1.5)_(1.3)g cm^(-3), indicating a rocky composition with an iron-to-silicate ratio consistent with that of the Earth. This makes Kepler-20b the most massive planet with a rocky composition found to date. Furthermore, we report the discovery of an additional non-transiting planet with a minimum mass of 19.96^(+3.08)_(-3.61)M⊕ and an orbital period of ~34 days in the gap between Kepler-20f (P ~ 11 days) and Kepler-20d (P ~ 78 days).

Item Type:Article
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URLURL TypeDescription Paper
Buchhave, Lars A.0000-0003-1605-5666
Dressing, Courtney D.0000-0001-8189-0233
Additional Information:© 2016 The American Astronomical Society. Received 2016 June 13; revised 2016 August 23; accepted 2016 August 24; published 2016 November 11. Based on observations made with the Italian Telescopio Nazionale Galileo (TNG) operated on the island of La Palma by the Fundación Galileo Galilei of the INAF (Istituto Nazionale di Astrofísica) at the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofísica de Canarias. The HARPS-N project was funded by the Prodex Program of the Swiss Space Office (SSO), the Harvard-University Origin of Life Initiative (HUOLI), the Scottish Universities Physics Alliance (SUPA), the University of Geneva, the Smithsonian Astrophysical Observatory (SAO), and the Italian National Astrophysical Institute (INAF), University of St. Andrews, Queen's University Belfast, and University of Edinburgh. The research leading to these results has received funding from the European Union Seventh Framework Programme (FP7/2007-2013) under Grant Agreement No. 313014 (ETAEARTH). This work was performed in part under contract with the California Institute of Technology/Jet Propulsion Laboratory, which is funded by NASA through the Sagan Fellowship Program executed by the NASA Exoplanet Science Institute. A.V. is supported by the NSF Graduate Research Fellowship, Grant No. DGE 1144152. This publication was made possible by a grant from the John Templeton Foundation. The opinions expressed in this publication are those of the authors and do not necessarily reflect the views of the John Templeton Foundation. This material is based upon work supported by NASA under grant No. NNX15AC90G issued through the Exoplanets Research Program. Funding for the Stellar Astrophysics Centre is provided by The Danish National Research Foundation (grant agreement no.: DNRF106). The research is supported by the ASTERISK project (ASTERoseismic Investigations with SONG and Kepler) funded by the European Research Council (Grant agreement no.: 267864). M.S.L. is supported by The Danish Council for Independent Research's Sapere Aude program (grant agreement no.: DFF—5051-00130). P.F. acknowledges support by Fundação para a Ciência e a Tecnologia (FCT) through Investigador FCT contract of reference IF/01037/2013 and POPH/FSE (EC) by FEDER funding through the program "Programa Operacional de Factores de Competitividade—COMPETE," and further support in the form of an exploratory project of reference IF/01037/2013CP1191/CT0001. The research leading to these results also received funding from the European Union Seventh Framework Programme (FP7/2007-2013) under grant agreement number 313014 (ETAEARTH). X.D. is grateful to the Society in Science–Branco Weiss Fellowship for its financial support. Software: SPC (Buchhave et al. 2012, 2014), ECCSAMPLES (Kipping 2014a), emcee (Fortney et al. 2013), BATMAN (Kreidberg 2015).
Funding AgencyGrant Number
Swiss Space Office (SSO)UNSPECIFIED
Harvard UniversityUNSPECIFIED
Scottish Universities Physics AllianceUNSPECIFIED
University of GenevaUNSPECIFIED
Smithsonian Astrophysical Observatory (SAO)UNSPECIFIED
Istituto Nazionale di Astrofisica (INAF)UNSPECIFIED
University of St. AndrewsUNSPECIFIED
Queen's UniversityUNSPECIFIED
University of EdinburghUNSPECIFIED
European Research Council (ERC)313014 (ETAEARTH)
NSF Graduate Research FellowshipDGE 1144152
John Templeton FoundationUNSPECIFIED
Danish National Research FoundationDNRF106
European Research Council (ERC)267864
Danish Council for Independent ResearchDFF-5051-00130
Fundação para a Ciência e a Tecnologia (FCT)IF/01037/2013
Fondo Europeo de Desarrollo Regional (FEDER)POPH/FSE
Fundação para a Ciência e a Tecnologia (FCT)IF/01037/2013CP1191/CT0001
Society in Science-Branco Weiss FellowshipUNSPECIFIED
Subject Keywords:planetary systems – planets and satellites: composition – stars: individual – techniques: radial velocities
Issue or Number:6
Record Number:CaltechAUTHORS:20161118-084227456
Persistent URL:
Official Citation:Lars A. Buchhave et al 2016 AJ 152 160
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:72150
Deposited By: Tony Diaz
Deposited On:18 Nov 2016 17:06
Last Modified:11 Nov 2021 04:57

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