M dwarf stars, which have masses less than 60 per cent that of the Sun, make up 75 per cent of the population of the stars in the Galaxy1. The atmospheres of orbiting Earth-sized planets are observationally accessible via transmission spectroscopy when the planets pass in front of these stars2,3. Statistical results suggest that the nearest transiting Earth-sized planet in the liquid-water, habitable zone of an M dwarf star is probably around 10.5 parsecs away4. A temperate planet has been discovered orbiting Proxima Centauri, the closest M dwarf5, but it probably does not transit and its true mass is unknown. Seven Earth-sized planets transit the very low-mass star TRAPPIST-1, which is 12 parsecs away6,7, but their masses and, particularly, their densities are poorly constrained. Here we report observations of LHS 1140b, a planet with a radius of 1.4 Earth radii transiting a small, cool star (LHS 1140) 12 parsecs away. We measure the mass of the planet to be 6.6 times that of Earth, consistent with a rocky bulk composition. LHS 1140b receives an insolation of 0.46 times that of Earth, placing it within the liquid-water, habitable zone8. With 90 per cent confidence, we place an upper limit on the orbital eccentricity of 0.29. The circular orbit is unlikely to be the result of tides and therefore was probably present at formation. Given its large surface gravity and cool insolation, the planet may have retained its atmosphere despite the greater luminosity (compared to the present-day) of its host star in its youth9,10. Because LHS 1140 is nearby, telescopes currently under construction might be able to search for specific atmospheric gases in the future2,3.

Access optionsAccess options

Rent or Buy article

Get time limited or full article access on ReadCube.


All prices are NET prices.


  1. 1.

    et al. The solar neighbourhood. XVII. Parallax results from the CTIOPI 0.9 m program: 20 new members of the RECONS 10 parsec sample. Astron. J. 132, 2360–2371 (2006)

  2. 2.

    & Feasibility studies for the detection of O2 in an Earth-like exoplanet. Astrophys. J. 781, 54 (2014)

  3. 3.

    et al. Finding extraterrestrial life using ground-based high-dispersion spectroscopy. Astrophys. J. 764, 182 (2013)

  4. 4.

    & The occurrence of potentially habitable planets orbiting M dwarfs estimated from the full Kepler dataset and an empirical measurement of the detection sensitivity. Astrophys. J. 807, 45 (2015)

  5. 5.

    et al. A terrestrial planet candidate in a temperate orbit around Proxima Centauri. Nature 536, 437–440 (2016)

  6. 6.

    et al. Temperate Earth-sized planets transiting a nearby ultracool dwarf star. Nature 533, 221–224 (2016)

  7. 7.

    et al. Seven temperate terrestrial planets around the nearby ultracool dwarf star TRAPPIST-1. Nature 542, 456–460 (2017)

  8. 8.

    et al. Habitable zones around main sequence stars: new estimates. Astrophys. J. 765, 131 (2013)

  9. 9.

    & Extreme water loss and abiotic O2 buildup on planets throughout the habitable zones of M dwarfs. Astrobiology 15, 119–143 (2015)

  10. 10.

    et al. Predictions of the atmospheric composition of GJ 1132b. Astrophys. J. 829, 63 (2016)

  11. 11.

    et al. Design considerations for a ground-based transit search for habitable planets orbiting M dwarfs. Publ. Astron. Soc. Pacif. 120, 317–327 (2008)

  12. 12.

    et al. The MEarth-North and MEarth-South transit surveys: searching for habitable super-Earth exoplanets around nearby M-dwarfs. In Proc. 18th Cambridge Workshop on Cool Stars, Stellar Systems, and the Sun (eds & ) 767–772 (2015)

  13. 13.

    et al. Transit detection in the MEarth survey of nearby M dwarfs: bridging the clean-first, search-later divide. Astron. J. 144, 145 (2012)

  14. 14.

    et al. The solar neighbourhood. XXXVIII. Results from the CTIO/SMARTS 0.9m: trigonometric parallaxes for 151 nearby M dwarf systems. Astron. J. 153, 14 (2017)

  15. 15.

    et al. The Two Micron All Sky Survey (2MASS). Astron. J. 131, 1163–1183 (2006)

  16. 16.

    et al. The solar neighbourhood. XXXVII. The mass-luminosity relation for main-sequence M dwarfs. Astron. J. 152, 141 (2016)

  17. 17.

    et al. Stellar diameters and temperatures. II. Main-sequence K- and M-stars. Astrophys. J. 757, 112 (2012)

  18. 18.

    et al. Setting new standards with HARPS. The Messenger 114, 20–24 (2003)

  19. 19.

    & Gaussian Processes for Machine Learning Ch. 3 (MIT Press, 2006)

  20. 20.

    et al. Planets and stellar activity: hide and seek in the CoRoT-7 system. Mon. Not. R. Astron. Soc. 443, 2517–2531 (2014)

  21. 21.

    & A detailed model grid for solid planets from 0.1 through 100 Earth masses. Publ. Astron. Soc. Pacif. 125, 227 (2013)

  22. 22.

    & The Kepler dichotomy among the M dwarfs: half of systems contain five or more coplanar planets. Astrophys. J. 816, 66 (2016)

  23. 23.

    et al. Kepler-445, Kepler-446 and the occurrence of compact multiples orbiting mid-M dwarf stars. Astrophys. J. 801, 18 (2015)

  24. 24.

    et al. Correlations between compositions and orbits established by the giant impact era. Astrophys. J. 822, 54 (2016)

  25. 25.

    et al. Accurate masses of very low mass star. IV. Improved mass-luminosity relations. Astron. Astrophys. 364, 217–224 (2000)

  26. 26.

    et al. The Dartmouth stellar evolution database. Astrophys. J. Suppl. Ser. 178, 89–101 (2008)

  27. 27.

    , & New evolutionary models for pre-main sequence and main sequence low-mass stars down to the hydrogen-burning limit. Astron. Astrophys. 577, A42 (2015)

  28. 28.

    & Intrinsic colors, temperatures, and bolometric corrections of pre-main-sequence stars. Astrophys. J. Suppl. Ser. 208, 9 (2013)

  29. 29.

    et al. Spectro-thermometry of M dwarfs and their candidate planets: too hot, too cool, or just right? Astrophys. J. 779, 188 (2013)

  30. 30.

    et al. A super-Earth transiting a nearby low-mass star. Nature 462, 891–894 (2009)

  31. 31.

    A rocky transiting planet transiting a nearby low-mass star. Nature 527, 204–207 (2015)

  32. 32.

    Neural Networks: A Comprehensive Foundation (Prentice Hall, 1998)

  33. 33.

    et al. Fundamental photon noise limit to radial velocity measurements. Astron. Astrophys. 374, 733–739 (2001)

  34. 34.

    et al. The HARPS search for southern extra-solar planets. Astron. Astrophys. 575, A119 (2015)

  35. 35.

    et al. New limb-darkening coefficients for PHOENIX/1D model atmospheres. I. Calculations for 1500 K ≤ Teff ≤ 4800 K. Kepler, CoRoT, Spitzer, uvby, UVBRIJHK, Sloan, and 2MASS photometric systems. Astron. Astrophys. 546, A14 (2012)

  36. 36.

    The solar-type eclipsing binary system LL Aquarii. Astron. Astrophys. 557, A119 (2013)

  37. 37.

    & Analytic light curves for planetary transit searches. Astrophys. J. 580, L171–L175 (2002)

  38. 38.

    et al. emcee: the MCMC Hammer. Publ. Astron. Soc. Pacif. 125, 306 (2013)

  39. 39.

    Least-squares frequency analysis of unequally spaced data. Astrophys. Space Sci. 39, 447–462 (1976)

  40. 40.

    Studies in astronomical time series analysis. II – statistical aspects of spectral analysis of unevenly spaced data. Astrophys. J. 263, 835–853 (1982)

  41. 41.

    et al. Search for exoplanets with the radial-velocity technique: quantitative diagnostics of stellar activity. Astron. Astrophys. 473, 983–993 (2007)

  42. 42.

    et al. Disentangling between stellar activity and planetary signals. Astron. Astrophys. 528, A4 (2011)

  43. 43.

    et al. The Sun as a planet-host star: proxies from SDO images for HARPS radial-velocity variations. Mon. Not. R. Astron. Soc. 457, 3637–3651 (2016)

  44. 44.

    et al. Using the Sun to estimate Earth-like planets detection capabilities. II Impact of plages. Astron. Astrophys. 512, A39 (2010)

  45. 45.

    et al. SOAP 2.0: a tool to estimate the photometric and radial-velocity variations induced by stellar spots and plages. Astrophys. J. 796, 132 (2014)

  46. 46.

    et al. Reconstructing the solar integrated radial velocity using MDI/SOHO. Astron. Astrophys. 519, A66 (2010)

  47. 47.

    et al. A simple method to estimate radial-velocity variations due to stellar activity using photometry. Mon. Not. R. Astron. Soc. 419, 3147–3158 (2012)

  48. 48.

    et al. Uncovering the planets and stellar activity of CoRoT-7 using only radial velocities. Astron. Astrophys. 588, A31 (2016)

  49. 49.

    et al. Determining the mass of Kepler-78b with nonparametric Gaussian process estimation. Astrophys. J. 808, 127 (2015)

  50. 50.

    et al. A Gaussian process framework for modelling stellar activity signals in radial-velocity data. Mon. Not. R. Astron. Soc. 452, 2269–2291 (2015)

  51. 51.

    et al. Kepler-21b: a rocky planet around a V = 8.25 magnitude star. Astron. J. 152, 204 (2016)

  52. 52.

    et al. SpeX: a medium-resolution 0.8-5.5 micron spectrograph and imager for the NASA Infrared Telescope Facility. Publ. Astron. Soc. Pacif. 115, 362–382 (2003)

  53. 53.

    et al. The Infrared Telescope Facility (IRTF) spectral library: cool stars. Astrophys. J. Suppl. Ser. 185, 289–432 (2009)

  54. 54.

    et al. An infrared spectroscopic sequence of M, L, and T dwarfs. Astrophys. J. 623, 1115–1140 (2005)

  55. 55.

    et al. Prospecting in late-type dwarfs: a calibration of infrared and visible spectroscopic metallicities of late K and M dwarfs spanning 1.5 dex. Astron. J. 145, 52 (2013)

  56. 56.

    et al. How to constrain your M Dwarf: measuring effective temperature, bolometric luminosity, mass, and radius. Astrophys. J. 804, 64 (2015); erratum 819, 87 (2016)

  57. 57.

    et al. Calibration of the MEarth photometric system: optical magnitudes and photometric metallicity estimates for 1802 nearby M-dwarfs. Astrophys. J. 818, 153 (2016)

  58. 58.

    et al. On the angular momentum evolution of fully-convective stars: rotation periods for field M-dwarfs from the MEarth transit survey. Astrophys. J. 727, 56 (2011)

  59. 59.

    et al. The rotation and galactic kinematics of mid M dwarfs in the solar neighborhood. Astrophys. J. 821, 93 (2016)

  60. 60.

    et al. Magnetic activity in the HARPS M-dwarf sample. The rotation-activity relationship for very low-mass stars through . Astron. Astrophys. 600, A13 (2017)

  61. 61.

    & The Galactic stellar disc. Phys. Scr. T133, 014031 (2008)

  62. 62.

    et al. Photometry of Proxima Centauri and Barnard’s star using Hubble Space Telescope Fine Guidance Sensor 3: a search for periodic variations. Astron. J. 116, 429–439 (1998)

  63. 63.

    & Calculating galactic space velocities and their uncertainties, with an application to the Ursa Major group. Astron. J. 93, 864–867 (1987)

  64. 64.

    et al. Local kinematics and the local standard of rest. Mon. Not. R. Astron. Soc. 403, 1829–1833 (2010)

  65. 65.

    et al. Exploring the local Milky Way: M dwarfs as tracers of Galactic populations. Astron. J. 134, 2418–2429 (2007)

  66. 66.

    et al. Constraining the age-activity relation for cool stars: the Sloan Digital Sky Survey data release 5 low-mass star spectroscopic sample. Astron. J. 135, 785–795 (2008)

  67. 67.

    et al. The Hα emission of nearby M dwarfs and its relation to stellar rotation. Astrophys. J. 834, 85 (2017)

  68. 68.

    & Improved age estimation for solar-type dwarfs using activity-rotation diagnostics. Astrophys. J. 687, 1264–1293 (2008)

  69. 69.

    , & Calculations of periodicity from Hα profiles of Proxima Centarui. Astron. Astrophys. (2017)

Download references


We thank the staff at the Cerro Tololo Inter-American Observatory for assistance in the construction and operation of MEarth-South. The MEarth team acknowledges funding from the David and Lucille Packard Fellowship for Science and Engineering (awarded to D.C.). This material is based on work supported by the National Science Foundation under grants AST-0807690, AST-1109468, AST-1004488 (Alan T. Waterman Award) and AST-1616624. This publication was made possible through the support of a grant from the John Templeton Foundation and NASA XRP Program #NNX15AC90G. The opinions expressed in this publication are those of the authors and do not necessarily reflect the views of the John Templeton Foundation. HARPS observations were made with European Southern Observatory (ESO) telescopes under observing programs 191.C-0873 and 198.C-0838. This work was performed in part under contract with the Jet Propulsion Laboratory (JPL) funded by NASA through the Sagan Fellowship Program executed by the NASA Exoplanet Science Institute. E.R.N. is supported by an NSF Astronomy and Astrophysics Postdoctoral Fellowship under award AST-1602597. N.C.S. acknowledges support from Fundação para a Ciência e a Tecnologia (FCT) through national funds and by FEDER through COMPETE2020 by grants UID/FIS/04434/2013&POCI-01-0145-FEDER-007672 and PTDC/FIS-AST/1526/2014&POCI-01-0145-FEDER-016886. N.C.S. was also supported by FCT through Investigador FCT contract reference IF/00169/2012/CP0150/CT0002. X.B., X.D. and T.F. acknowledge the support of the INSU/PNP (Programme national de planétologie) and INSU/PNPS (Programme national de physique stellaire). X.B., J.-M.A. and A.W. acknowledge funding from the European Research Council under ERC Grant Agreement no. 337591-ExTrA. We thank A. Vanderburg for backseat MCMCing. This publication makes use of data products from the Two Micron All Sky Survey (2MASS), which is a joint project of the University of Massachusetts and the Infrared Processing and Analysis Center/California Institute of Technology, funded by NASA and the National Science Foundation. This publication makes use of data products from the Wide-field Infrared Survey Explorer, which is a joint project of the University of California, Los Angeles, and the JPL/California Institute of Technology, funded by NASA. This research has made extensive use of the NASA Astrophysics Data System (ADS), and the SIMBAD database, operated at CDS, Strasbourg, France.

Author information


  1. Harvard Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, Massachusetts 02138, USA

    • Jason A. Dittmann
    • , Jonathan M. Irwin
    • , David Charbonneau
    • , Raphaëlle D. Haywood
    • , Joseph E. Rodriguez
    • , Jennifer G. Winters
    • , Gilbert A. Esquerdo
    •  & David W. Latham
  2. CNRS (Centre National de la Recherche Scientifique), IPAG (Institut de Planétologie et d’Astrophysique de Grenoble), F-38000 Grenoble, France

    • Xavier Bonfils
    • , Jose-Manuel Almenara
    • , Xavier Delfosse
    • , Thierry Forveille
    • , Felipe Murgas
    •  & Anaël Wünsche
  3. Université Grenoble Alpes, CNRS, IPAG, F-38000 Grenoble, France

    • Xavier Bonfils
    • , Jose-Manuel Almenara
    • , Xavier Delfosse
    • , Thierry Forveille
    • , Felipe Murgas
    •  & Anaël Wünsche
  4. Observatoire de Genève, Université de Genève, 51 chemin des Maillettes, 1290 Versoix, Switzerland

    • Nicola Astudillo-Defru
    • , Jose-Manuel Almenara
    • , Christophe Lovis
    • , Francesco Pepe
    •  & Stephane Udry
  5. University of Colorado, 391 UCB, 2000 Colorado Avenue, Boulder, Colorado 80305, USA

    • Zachory K. Berta-Thompson
  6. Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02138, USA

    • Elisabeth R. Newton
  7. Perth Exoplanet Survey Telescope, Perth, Western Australia, Australia

    • Thiam-Guan Tan
  8. Aix Marseille Université, CNRS, LAM (Laboratoire d’Astrophysique de Marseille) UMR 7326, 13388 Marseille, France

    • François Bouchy
  9. Instituto de Astrofísica de Canarias (IAC), E-38205 La Laguna, Tenerife, Spain

    • Felipe Murgas
  10. Instituto de Astrofísica e Ciéncias do Espaço, Universidade do Porto, CAUP (Centro de Astrofísica da Universidade do Porto), Rua das Estrelas, 4150-762 Porto, Portugal

    • Nuno C. Santos
  11. Departamento de Física e Astronomia, Faculdade de Ciências, Universidade do Porto, Rua do Campo, Alegre, 4169-007 Porto, Portugal

    • Nuno C. Santos
  12. Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California 91125, USA

    • Courtney D. Dressing


  1. Search for Jason A. Dittmann in:

  2. Search for Jonathan M. Irwin in:

  3. Search for David Charbonneau in:

  4. Search for Xavier Bonfils in:

  5. Search for Nicola Astudillo-Defru in:

  6. Search for Raphaëlle D. Haywood in:

  7. Search for Zachory K. Berta-Thompson in:

  8. Search for Elisabeth R. Newton in:

  9. Search for Joseph E. Rodriguez in:

  10. Search for Jennifer G. Winters in:

  11. Search for Thiam-Guan Tan in:

  12. Search for Jose-Manuel Almenara in:

  13. Search for François Bouchy in:

  14. Search for Xavier Delfosse in:

  15. Search for Thierry Forveille in:

  16. Search for Christophe Lovis in:

  17. Search for Felipe Murgas in:

  18. Search for Francesco Pepe in:

  19. Search for Nuno C. Santos in:

  20. Search for Stephane Udry in:

  21. Search for Anaël Wünsche in:

  22. Search for Gilbert A. Esquerdo in:

  23. Search for David W. Latham in:

  24. Search for Courtney D. Dressing in:


The MEarth team (J.A.D., D.C., J.M.I., Z.K.B.-T., E.R.N., J.G.W. and J.E.R.) discovered the planet, organized the follow-up observations, and led the analysis and interpretation. J.A.D. analysed the light curve and the radial-velocity data and wrote the manuscript. J.M.I. designed and installed, and maintains and operates the MEarth-South telescope array, and contributed to the analysis and interpretation. D.C. leads the MEarth project, and assisted in analysis and writing the manuscript. E.R.N. determined the rotational period of the star. R.D.H. conducted the Gaussian process analysis of the radial velocities. J.E.R. and T.-G.T. organized the follow-up effort in Perth. The HARPS team (X.B., N.A.-D., J.-M.A., F.B., X.D., T.F., C.L., F.M., F.P., N.C.S., S.U. and A.W.) obtained spectra for Doppler velocimetry, with N.A.-D. and X.B. leading the analysis of those data. G.A.E. and D.W.L. obtained the reconnaissance spectrum with TRES at FLWO. C.D.D. obtained the infrared spectrum with IRTF/SpeX and determined the stellar metallicity.

Competing interests

The authors declare no competing financial interests.

Corresponding author

Correspondence to Jason A. Dittmann.

Reviewer Information Nature thanks A. Hatzes and the other anonymous reviewer(s) for their contribution to the peer review of this work.

Publisher's note: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Extended data

Supplementary information

Text files

  1. 1.

    Supplementary Data

    This file contains all radial velocity data taken with the HARPS spectrograph.

  2. 2.

    Supplementary Data

    This file contains all MEarth and PEST photometric transit data taken of LHS 1140b.

About this article

Publication history





Further reading

  • A Catalog of Smaller Planets

    • Barton Paul Levenson

    Earth, Moon, and Planets (2019)

  • An Earth-sized exoplanet with a Mercury-like composition

    • A. Santerne
    • , B. Brugger
    • , D. J. Armstrong
    • , V. Adibekyan
    • , J. Lillo-Box
    • , H. Gosselin
    • , A. Aguichine
    • , J.-M. Almenara
    • , D. Barrado
    • , S. C. C. Barros
    • , D. Bayliss
    • , I. Boisse
    • , A. S. Bonomo
    • , F. Bouchy
    • , D. J. A. Brown
    • , M. Deleuil
    • , E. Delgado Mena
    • , O. Demangeon
    • , R. F. Díaz
    • , A. Doyle
    • , X. Dumusque
    • , F. Faedi
    • , J. P. Faria
    • , P. Figueira
    • , E. Foxell
    • , H. Giles
    • , G. Hébrard
    • , S. Hojjatpanah
    • , M. Hobson
    • , J. Jackman
    • , G. King
    • , J. Kirk
    • , K. W. F. Lam
    • , R. Ligi
    • , C. Lovis
    • , T. Louden
    • , J. McCormac
    • , O. Mousis
    • , J. J. Neal
    • , H. P. Osborn
    • , F. Pepe
    • , D. Pollacco
    • , N. C. Santos
    • , S. G. Sousa
    • , S. Udry
    •  & A. Vigan

    Nature Astronomy (2018)

  • Water Loss from Young Planets

    • Feng Tian
    • , Manuel Güdel
    • , Colin P. Johnstone
    • , Helmut Lammer
    • , Rodrigo Luger
    •  & Petra Odert

    Space Science Reviews (2018)


By submitting a comment you agree to abide by our Terms and Community Guidelines. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate.