Two massive rocky planets transiting a K-dwarf 6.5 parsecs away

DOI
Publisher DOI
Abstract
HD 219134 is a K-dwarf star at a distance of 6.5 parsecs around which several low-mass planets were recently discovered1,2. The Spitzer Space Telescope detected a transit of the innermost of these planets, HD 219134 b, whose mass and radius (4.5 M⊕ and 1.6 R⊕ respectively) are consistent with a rocky composition1. Here, we report new high-precision time-series photometry of the star acquired with Spitzer revealing that the second innermost planet of the system, HD 219134c, is also transiting. A global analysis of the Spitzer transit light curves and the most up-to-date HARPS-N velocity data set yields mass and radius estimations of 4.74 ± 0.19 M⊕ and 1.602 ± 0.055 R⊕ for HD 219134 b, and of 4.36 ± 0.22 M⊕ and 1.511 ± 0.047 R⊕ for HD 219134 c. These values suggest rocky compositions for both planets. Thanks to the proximity and the small size of their host star (0.778 ± 0.005 R⊙)3, these two transiting exoplanets — the nearest to the Earth yet found — are well suited for a detailed characterization (for example, precision of a few per cent on mass and radius, and constraints on the atmospheric properties) that could give important constraints on the nature and formation mechanism of the ubiquitous short-period planets of a few Earth masses.
Date Issued
2017
Publication Type
Article
Subject(s)
Language(s)
en
Author(s)
Gillon, Michaël
Van Grootel, Valérie
Motalebi, Fatemeh
Lovis, Christophe
Cameron, Andrew Collier
Charbonneau, David
Latham, David
Molinari, Emilio
Pepe, Francesco A.
Ségransan, Damien
Sasselov, Dimitar
Udry, Stéphane
Mayor, Michel
Micela, Giuseppina
Piotto, Giampaolo
Sozzetti, Alessandro
Additional Credits
Journal
Nature astronomy
Publisher
Nature Publishing Group
ISSN
2397-3366
Access(Rights)
restricted
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