A Caltech Library Service

Seven temperate terrestrial planets around the nearby ultracool dwarf star TRAPPIST-1

Gillon, Michaël and Deck, Katherine M. and Ingalls, James G. and Carey, Sean J. (2017) Seven temperate terrestrial planets around the nearby ultracool dwarf star TRAPPIST-1. Nature, 542 (7642). pp. 456-460. ISSN 0028-0836. PMCID PMC5330437.

[img] PDF - Accepted Version
See Usage Policy.

[img] Image (JPEG) (Extended Data Figure 1: Light curve of a triple transit of planets c, e and f) - Supplemental Material
See Usage Policy.

[img] Image (JPEG) (Extended Data Figure 2: Transit light curve for planets d and e) - Supplemental Material
See Usage Policy.

[img] Image (JPEG) (Extended Data Figure 3: Transit light curves for planets f and g) - Supplemental Material
See Usage Policy.

[img] Image (JPEG) (Extended Data Figure 4: TTVs measured for planets b, c, d, e, f and g) - Supplemental Material
See Usage Policy.

[img] Image (JPEG) (Extended Data Table 1: Summary of the observation set used) - Supplemental Material
See Usage Policy.


Use this Persistent URL to link to this item:


One aim of modern astronomy is to detect temperate, Earth-like exoplanets that are well suited for atmospheric characterization. Recently, three Earth-sized planets were detected that transit (that is, pass in front of) a star with a mass just eight per cent that of the Sun, located 12 parsecs away. The transiting configuration of these planets, combined with the Jupiter-like size of their host star—named TRAPPIST-1—makes possible in-depth studies of their atmospheric properties with present-day and future astronomical facilities. Here we report the results of a photometric monitoring campaign of that star from the ground and space. Our observations reveal that at least seven planets with sizes and masses similar to those of Earth revolve around TRAPPIST-1. The six inner planets form a near-resonant chain, such that their orbital periods (1.51, 2.42, 4.04, 6.06, 9.1 and 12.35 days) are near-ratios of small integers. This architecture suggests that the planets formed farther from the star and migrated inwards. Moreover, the seven planets have equilibrium temperatures low enough to make possible the presence of liquid water on their surfaces.

Item Type:Article
Related URLs:
URLURL TypeDescription ReadCube access CentralArticle
Gillon, Michaël0000-0003-1462-7739
Ingalls, James G.0000-0003-4714-1364
Carey, Sean J.0000-0002-0221-6871
Additional Information:© 2017 Macmillan Publishers Limited, part of Springer Nature. Received 21 November 2016; Accepted 21 December 2016; Published online 22 February 2017. This work is based in part on observations made with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under a contract with NASA. The material presented here is based on work supported in part by NASA under contract no. NNX15AI75G. TRAPPIST-South is a project funded by the Belgian Fonds (National) de la Recherche Scientifique (F.R.S.-FNRS) under grant FRFC 2.5.594.09.F, with the participation of the Swiss National Science Foundation (FNS/SNSF). TRAPPIST-North is a project funded by the University of Liège, and performed in collaboration with Cadi Ayyad University of Marrakesh. The research leading to these results has received funding from the European Research Council (ERC) under the FP/2007-2013 ERC grant agreement no. 336480, and under the H2020 ERC grant agreement no. 679030; and from an Actions de Recherche Concertée (ARC) grant, financed by the Wallonia–Brussels Federation. The VLT data used in this work were taken under program 296.C-5010(A). UKIRT is supported by NASA and operated under an agreement among the University of Hawaii, the University of Arizona, and Lockheed Martin Advanced Technology Center; operations are enabled through the cooperation of the East Asian Observatory. The Liverpool Telescope is operated on the island of La Palma by Liverpool John Moores University (JMU) in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofisica de Canarias, with financial support from the UK Science and Technology Facilities Council. This paper uses observations made at the South African Astronomical Observatory (SAAO). M.G., E.J. and V.V.G. are F.R.S.-FNRS research associates. B.-O.D. acknowledges support from the Swiss National Science Foundation in the form of a SNSF Professorship (PP00P2_163967). E.A. acknowledges support from National Science Foundation (NSF) grant AST-1615315, and NASA grants NNX13AF62G and NNH05ZDA001C. E.B. acknowledges that this work is part of the F.R.S.-FNRS ExtraOrDynHa research project and acknowledges funding by the European Research Council through ERC grant SPIRE 647383. S.N.R. thanks the Agence Nationale pour la Recherche (ANR) for support via grant ANR-13-BS05-0003-002 (project MOJO). D.L.H. acknowledges financial support from the UK Science and Technology Facilities Council. The authors thank C. Owen, C. Wolf and the rest of the SkyMapper team for their attempts to monitor the star from Australia; from UKIRT, the director R. Green and the staff scientists W. Varricatt and T. Kerr; the ESO staff at Paranal for their support with the HAWK-I observations; JMU and their flexibility as regards the Liverpool Telescope schedule, which allowed us to search actively for the planets, and to extend our time allocation in the face of amazing results; for the William Herschel Telescope, C. Fariña, F. Riddick, F. Jímenez and O. Vaduvescu for their help and kindness during observations; and for SAAO, the telescopes operations manager R. Sefako for his support. Author Contributions: M.G. leads the ultracool dwarf transit survey that uses the TRAPPIST telescope and led the photometric follow-up of the star TRAPPIST-1; he also planned and analysed most of the observations, led their scientific exploitation, and wrote most of the manuscript. A.H.M.J.T. led the observational campaign using the La Palma telescopes (the Liverpool Telescope, LT, and William Herschel Telescope, WHT). C.M.C. managed the scheduling of the LT observations, and Ar.B. performed the photometric analysis of the resulting LT and WHT images. B.-O.D. led the TTV/dynamical simulations. E.A. and K.M.D. performed independent analyses of the transit timings. J.G.I. and S.J.C. helped to optimize the Spitzer observations. B.-O.D., J.G.I. and J.d.W. performed independent analyses of the Spitzer data. M.G., E.J., L.D., Ar.B., P.M., K.B., Y.A. and Z.B. performed the TRAPPIST observations and their analysis. S.M.L. obtained the director’s discretionary time on UKIRT, and, with E.J., managed the preparation of the UKIRT observations. M.T., J.L., F.S., E.B. and S.N.R. carried out atmospheric modelling for the planets and worked on the theoretical interpretation of their properties. V.V.G. managed the SAAO observations performed by C.S.F., M.R.B., D.L.H., A.C. and E.J.K. All co-authors assisted with writing the manuscript. A.H.M.J.T. prepared most of the figures. The authors declare no competing financial interests.
Group:Infrared Processing and Analysis Center (IPAC)
Funding AgencyGrant Number
Fonds National de la Recherche Scientifique (FNRS)2.5.594.09.F
University of LiègeUNSPECIFIED
European Research Council (ERC)336480
European Research Council (ERC)679030
Actions de recherche concertées – Wallonia-Brussels FederationUNSPECIFIED
Science and Technology Facilities Council (STFC)UNSPECIFIED
Swiss National Science Foundation (SNSF)PP00P2_163967
European Research Council (ERC)647383
Agence Nationale pour la Recherche (ANR)ANR-13-BS05-0003-002
Subject Keywords:Astrobiology; Exoplanets
Issue or Number:7642
PubMed Central ID:PMC5330437
Record Number:CaltechAUTHORS:20170222-103759123
Persistent URL:
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:74466
Deposited By: Tony Diaz
Deposited On:22 Feb 2017 18:58
Last Modified:14 Nov 2019 23:43

Repository Staff Only: item control page