A 1.9 Earth radius rocky planet and the discovery of a non-transiting planet in the Kepler-20 system
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Date
11/11/2016Author
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Grant ID
ST/M001296/1
ST/I000666/1
PP/D000890/1
ST/G001006/1
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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 publications in the literature (Rogers 2015; Weiss& Marcy 2014). Kepler-20b (Rp ∼ 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 Kepler-20 three of the planets in the Kepler-20 system 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 amass 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).
Citation
Buchhave , L A , Dressing , C D , Dumusque , X , Rice , K , Vanderburg , A , Mortier , A , Lopez-Morales , M , Lopez , E , Lundkvist , M S , Kjeldsen , H , Affer , L , Bonomo , A S , Charbonneau , D , Cameron , A C , Cosentino , R , Figueira , P , Fiorenzano , A F M , Harutyunyan , A , Haywood , R D , Johnson , J A , Latham , D W , Lovis , C , Malavolta , L , Mayor , M , Micela , G , Molinari , E , Motalebi , F , Nascimbeni , V , Pepe , F , Phillips , D F , Piotto , G , Pollacco , D , Queloz , D , Sasselov , D , Ségransan , D , Sozzetti , A , Udry , S & Watson , C 2016 , ' A 1.9 Earth radius rocky planet and the discovery of a non-transiting planet in the Kepler-20 system ' , Astronomical Journal , vol. 152 , no. 6 , 160 . https://doi.org/10.3847/0004-6256/152/6/160
Publication
Astronomical Journal
Status
Peer reviewed
ISSN
0004-6256Type
Journal article
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