At a distance of 1.295 parsecs1, the red dwarf Proxima Centauri (α Centauri C, GL 551, HIP 70890 or simply Proxima) is the Sun’s closest stellar neighbour and one of the best-studied low-mass stars. It has an effective temperature of only around 3,050 kelvin, a luminosity of 0.15 per cent of that of the Sun, a measured radius of 14 per cent of the radius of the Sun2 and a mass of about 12 per cent of the mass of the Sun. Although Proxima is considered a moderately active star, its rotation period is about 83 days (ref. 3) and its quiescent activity levels and X-ray luminosity4 are comparable to those of the Sun. Here we report observations that reveal the presence of a small planet with a minimum mass of about 1.3 Earth masses orbiting Proxima with a period of approximately 11.2 days at a semi-major-axis distance of around 0.05 astronomical units. Its equilibrium temperature is within the range where water could be liquid on its surface5.
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van Leeuwen, F. Validation of the new Hipparcos reduction. Astron. Astrophys. 474, 653–664 (2007)
Boyajian, T. S. et al. Stellar diameters and temperatures. II: Main-sequence K- and M-stars. Astrophys. J. 757, 112 (2012)
Kiraga, M. & Stepien, K. Age–rotation–activity relations for M dwarf stars. Acta Astron. 57, 149–172 (2007)
Güdel, M., Audard, M., Reale, F., Skinner, S. L. & Linsky, J. L. Flares from small to large: X-ray spectroscopy of Proxima Centauri with XMM-Newton. Astron. Astrophys. 416, 713–732 (2004)
Kopparapu, R. K. et al. Habitable zones around main-sequence stars: new estimates. Astrophys. J. 765, 131 (2013)
Pepe, F. et al. The HARPS search for Earth-like planets in the habitable zone. I. Very low-mass planets around HD 20794, HD 85512, and HD 192310. Astron. Astrophys. 534, A58 (2011)
Anglada-Escudé, G. & Butler, R. P. The HARPS-TERRA Project. I: description of the algorithms, performance, and new measurements on a few remarkable stars observed by HARPS. Astrophys. J. Suppl. Ser. 200, 15 (2012)
Butler, R. P. et al. Attaining Doppler precision of 3 m s−1. Publ. Astron. Soc. Pacif. 108, 500–509 (1996)
Kürster, M. et al. The low-level radial velocity variability in Barnard’s star (= GJ 699): secular acceleration, indications for convective redshift, and planet mass limits. Astron. Astrophys. 403, 1077–1087 (2003)
Arriagada, P. et al. Two planetary companions around the K7 dwarf GJ 221: a hot super-Earth and a candidate in the sub-Saturn desert range. Astrophys. J. 771, 42 (2013)
Berdiñas, Z. M., Amado, P. J., Anglada-Escudé, G., Rodríguez-López, C. & Barnes, J. High-cadence spectroscopy of M-dwarfs. I: analysis of systematic effects in HARPS-N line profile measurements on the bright binary GJ 725A+B. Mon. Not. R. Astron. Soc. 459, 3551B (2016)
Sicardy, B. et al. A Pluto-like radius and a high albedo for the dwarf planet Eris from an occultation. Nature 478, 493–496 (2011)
Brown, T. M. et al. Las Cumbres Observatory Global Telescope Network. Publ. Astron. Soc. Pacific 125, 1031–1055 (2013)
Baluev, R. V. The impact of red noise in radial velocity planet searches: only three planets orbiting GJ 581? Mon. Not. R. Astron. Soc. 429, 2052–2068 (2013)
Tuomi, M., Jones, H. R. A., Barnes, J. R., Anglada-Escudé, G. & Jenkins, J. S. Bayesian search for low-mass planets around nearby M dwarfs—estimates for occurrence rate based on global detectability statistics. Mon. Not. R. Astron. Soc. 441, 1545–1569 (2014)
Haario, H., Laine, M., Mira, A. & Saksman, E. Dram: efficient adaptive MCMC. Stat. Comput. 16, 339–354 (2006)
Rajpaul, V., Aigrain, S. & Roberts, S. Ghost in the time series: no planet for Alpha Cen B. Mon. Not. R. Astron. Soc. 456, L6–L10 (2016)
Bonfils, X. et al. The HARPS search for southern extra-solar planets. X: A msini = 11M⊕ planet around the nearby spotted M dwarf GJ 674. Astron. Astrophys. 474, 293–299 (2007)
Barnes, J. R. et al. Precision radial velocities of 15 M5–M9 dwarfs. Mon. Not. R. Astron. Soc. 439, 3094–3113 (2014)
Ofir, A. Optimizing the search for transiting planets in long time series. Astron. Astrophys. 561, A138 (2014)
Kopparapu, R. k. et al. The inner edge of the habitable zone for synchronously rotating planets around low-mass stars using general circulation models. Astrophys. J. 819, 84 (2016)
Reiners, A. & Basri, G. The moderate magnetic field of the flare star Proxima Centauri. Astron. Astrophys. 489, L45–L48 (2008)
Vidotto, A. A. et al. Effects of M dwarf magnetic fields on potentially habitable planets. Astron. Astrophys. 557, A67 (2013)
Zuluaga, J. I., Bustamante, S., Cuartas, P. A. & Hoyos, J. H. The influence of thermal evolution in the magnetic protection of terrestrial planets. Astrophys. J. 770, 23 (2013)
Bolmont, E. et al. Water loss from Earth-sized planets in the habitable zones of ultracool dwarfs: implications for the planets of TRAPPIST-1. Preprint at http://arxiv.org/abs/1605.00616 (2016)
Tanaka, H., Takeuchi, T. & Ward, W. R. Three-dimensional interaction between a planet and an isothermal gaseous disk. I: corotation and Lindblad torques and planet migration. Astrophys. J. 565, 1257–1274 (2002)
Weidenschilling, S. J. Aerodynamics of solid bodies in the solar nebula. Mon. Not. R. Astron. Soc. 180, 57–70 (1977)
Snellen, I. et al. Combining high-dispersion spectroscopy with high contrast imaging: probing rocky planets around our nearest neighbors. Astron. Astrophys. 576, A59 (2015)
Lubin, P. A roadmap to interstellar flight. Preprint at http://arxiv.org/abs/1604.01356 (2016)
Delfosse, X. et al. Accurate masses of very low mass stars. IV. Improved mass-luminosity relations. Astron. Astrophys. 364, 217–224 (2000)
Haario, H., Saksman, E. & Tamminen, J. An adaptive Metropolis algorithm. Bernouilli 7, 223 (2001)
Tuomi, M. et al. Signals embedded in the radial velocity noise: periodic variations in the τ Ceti velocities. Astron. Astrophys. 551, A79 (2013)
Metropolis, N., Rosenbluth, A., Rosenbluth, M., Teller, A. & Teller, E. Equations of state valculations by fast computing machines. J. Chem. Phys. 21, 1087–1092 (1953)
Hastings, W. K. Monte Carlo sampling methods using Markov chains and their applications. Biometrika 57, 97–109 (1970)
Newton, M. A. & Raftery, A. E. Approximate Bayesian inference with the weighted likelihood bootstrap. J. R. Stat.Soc. B 56, 3–48 (1994)
Tuomi, M. A new cold sub-Saturnian candidate planet orbiting GJ 221. Mon. Not. R. Astron. Soc. 440, L1–L5 (2014)
Wright, J. T. & Howard, A. W. Efficient fitting of multiplanet Keplerian models to radial velocity and astrometry data. Astrophys. J. Suppl. Ser. 182, 205–215 (2009)
Scargle, J. D. Studies in astronomical time series analysis. I: modeling random processes in the time domain. Astrophys. J. Suppl. Ser. 45, 1–71 (1981)
Tuomi, M. Evidence for nine planets in the HD 10180 system. Astron. Astrophys. 543, A52 (2012)
Tuomi, M. & Anglada-Escudé, G. Up to four planets around the M dwarf GJ 163: sensitivity of Bayesian planet detection criteria to prior choice. Astron. Astrophys. 556, A111 (2013)
Berger, J. O. Statistical Decision Theory and Bayesian Analysis Section 3.3 (Springer, 1980)
Anglada-Escudé, G. et al. A dynamically-packed planetary system around GJ 667C with three super-Earths in its habitable zone. Astron. Astrophys. 556, A126 (2013)
Lomb, N. R. Least-squares frequency analysis of unequally spaced data. Astrophys. Space Sci. 39, 447–462 (1976)
Scargle, J. D. Studies in astronomical time series analysis. II: statistical aspects of spectral analysis of unevenly spaced data. Astrophys. J. 263, 835–853 (1982)
Zechmeister, M., Kürster, M. & Endl, M. The M dwarf planet search programme at the ESO VLT + UVES: a search for terrestrial planets in the habitable zone of M dwarfs. Astron. Astrophys. 505, 859–871 (2009)
Cumming, A. Detectability of extrasolar planets in radial velocity surveys. Mon. Not. R. Astron. Soc. 354, 1165–1176 (2004)
Ferraz-Mello, S. Estimation of periods from unequally spaced observations. Astron. J. 86, 619–624 (1981)
Baluev, R. V. Accounting for velocity jitter in planet search surveys. Mon. Not. R. Astron. Soc. 393, 969–978 (2009)
Endl, M. & Kürster, M. Toward detection of terrestrial planets in the habitable zone of our closest neighbor: Proxima Centauri. Astron. Astrophys. 488, 1149–1153 (2008)
Bonfils, X. et al. The HARPS search for southern extra-solar planets. XXXI: the M-dwarf sample. Astron. Astrophys. 549, A109 (2013)
Queloz, D. et al. No planet for HD 166435. Astron. Astrophys. 379, 279–287 (2001)
Robertson, P., Mahadevan, S., Endl, M. & Roy, A. Stellar activity masquerading as planets in the habitable zone of the M dwarf Gliese 581. Science 345, 440–444 (2014)
Donati, J.-F. & Brown, S. F. Zeeman–Doppler imaging of active stars. V: sensitivity of maximum entropy magnetic maps to field orientation. Astron. Astrophys. 326, 1135–1142 (1997)
Barnes, J. R. et al. Red Optical Planet Survey: a new search for habitable Earths in the southern sky. Mon. Not. R. Astron. Soc. 424, 591–604 (2012)
Press, W. H., Teukolsky, S. A., Vetterling, W. T. & Flannery, B. P. Numerical Recipes in FORTRAN. The Art of Scientific Computing 2nd edn, Section 4.1 (Cambridge Univ. Press, 1992)
Jenkins, J. S. et al. An activity catalogue of southern stars. Mon. Not. R. Astron. Soc. 372, 163–173 (2006)
Jenkins, J. S. et al. Metallicities and activities of southern stars. Astron. Astrophys. 485, 571–584 (2008)
Collins, K. A., Kielkopf, J. F. & Stassun, K. G. AstroImageJ: image processing and photometric extraction for ultra-precise astronomical light curves. Preprint at http://arxiv.org/abs/1601.02622 (2016)
Southworth, J. et al. High-precision photometry by telescope defocussing. VI: WASP-24, WASP-25 and WASP-26. Mon. Not. R. Astron. Soc. 444, 776–789 (2014)
Dawson, R. I. & Fabrycky, D. C. Radial velocity planets de-aliased: a new, short period for super-Earth 55 Cnc e. Astrophys. J. 722, 937–953 (2010)
Aigrain, S., Pont, F. & Zucker, S. A simple method to estimate radial velocity variations due to stellar activity using photometry. Mon. Not. R. Astron. Soc. 419, 3147–3158 (2012)
Gomes da Silva, J. et al. Long-term magnetic activity of a sample of M-dwarf stars from the HARPS program. II: activity and radial velocity. Astron. Astrophys. 541, A9 (2012)
Baliunas, S. L. et al. Chromospheric variations in main-sequence stars. Astrophys. J. 438, 269–287 (1995)
Pascual-Granado, J., Garrido, R. & Suárez, J. C. Limits in the application of harmonic analysis to pulsating stars. Astron. Astrophys. 581, A89 (2015)
We thank E. Gerlach, R. Street and U. Seemann for their support to the science preparations. We thank P. Micakovic, M. M. Mutter (QMUL), R. Ivison, G. Hussain, I. Saviane, O. Sandu, L. L. Christensen, R. Hook and the personnel at La Silla (ESO) for making the PRD campaign possible. The authors acknowledge support from the following funding grants: Leverhulme Trust/UK RPG-2014-281 (H.R.A.J., G.A.-E. and M.T.); MINECO/Spain AYA-2014-54348-C3-1-R (P.J.A., C.R.-L., Z.M.B. and E.R.); MINECO/Spain ESP2014-54362-P (M.J.L.-G.); MINECO/Spain AYA-2014-56637-C2-1-P (J.L.O. and N.M.); J.A./Spain 2012-FQM1776 (J.L.O. and N.M.); CATA-Basal/Chile PB06 Conicyt (J.S.J.); Fondecyt/Chile project #1161218 (J.S.J.); STFC/UK ST/M001008/1 (R.P.N., G.A.L.C. and G.A.-E.); STFC/UK ST/L000776/1 (J.B.); ERC/EU Starting Grant #279347 (A.R., L.F.S. and S.V.J.); DFG/Germany Research Grants RE 1664/9-2 (A.R.); RE 1664/12-1 (M.Z.); DFG/Germany Colloborative Research Center 963 (C.J.M. and S.D.); DFG/Germany Research Training Group 1351 (L.F.S.); and NSF/USA grant AST-1313075 (M.E.). Study based on observations made with ESO Telescopes at the La Silla Paranal Observatory under programmes 096.C-0082 and 191.C-0505. Observations were obtained with ASH2, which is supported by the Instituto de Astrofísica de Andalucía and Astroimagen. This work makes use of observations from the LCOGT network. We acknowledge the effort of the UVES/M-dwarf and the HARPS/Geneva teams, who obtained a substantial amount of the data used in this work.
The authors declare no competing financial interests.
Nature thanks A. Hatzes and D. Queloz for their contribution to the peer review of this work.
Extended data figures and tables
a–c, Window function of the UVES (a), HARPS pre-2016 (b) and HARPS PRD (c) data sets. The same window function applies to the time series of Doppler and activity data. Peaks in the window function are periods at which aliases of infinite period signals would be expected. The green vertical lines mark the period of the planet candidate at 11.2 d.
a–c, Likelihood-ratio periodograms searches on the radial velocity (RV) measurements of the UVES (a), HARPS pre-2016 (b) and HARPS PRD (c) subsets. The periodogram with all three sets combined is shown in Fig. 1. The black and red lines represent the searches for the first and second signals, respectively. The green vertical lines mark the period of the planet candidate at 11.2 d.
a–d, Likelihood-ratio periodograms searches for signals in each photometric ASH2 photometric band (a, b) and LCOGT bands (c, d). The two sinusoid fits to the ASH2 S ii series (P1 = 84 d, P2 = 39.1 d) are used later to construct the FF′ model to test for correlations of the photometry with the radial velocity data. The black, red and blue lines represent the search for the first, second and third signal respectively. The green vertical lines mark the period of the planet candidate at 11.2 d.
a, b, Likelihood-ratio periodogram searches on the width of the mean spectral line as measured by m2 for the HARPS pre-2016 (a) and HARPS PRD data (b). The signals in the HARPS pre-2016 data are comparable to the photometric period reported in the literature and the variability in the HARPS PRD run compares quite well to the photometric variability. The black, red and blue lines represent the search for the first, second and third signal, respectively. The green vertical lines mark the period of the planet candidate at 11.2 d.
a, b, Likelihood-ratio periodogram searches on the line asymmetry as measured by m3 from the HARPS pre-2016 (a) and HARPS PRD (b) data sets. Signal beating at around 1 yr and 0.5 yr is detected in the HARPS pre-2016 data, which is possibly related to instrumental systematic effects or telluric contamination. No signals are detected above the 1% threshold in the HARPS PRD campaign. The black and red lines represent the search for the first and second signals respectively. The green vertical lines mark the period of the planet candidate at 11.2 d.
a, b, Likelihood-ratio periodogram of the S-index from the HARPS pre-2016 (a) and HARPS PRD (b) campaigns. No signals were detected above the 1% threshold. The green vertical lines mark the period of the planet candidate at 11.2 d.
a–c, Likelihood-ratio periodogram searches of Hα intensity from the UVES (a), HARPS pre-2016 (b) and HARPS PRD (c) campaigns. No signals were detected above the 1% threshold. The green vertical lines mark the period of the planet candidate at 11.2 d.
a–d, Radial velocities (a) and equivalent width measurements of the Hα (b), Na doublet lines (c) and the S-index (d) as a function of time during a flare that occurred the night of 5 May 2013. The time axis is days since jd = 245417.0 d. No trace of the flare is observed in the radial velocities. Error bars in the radial velocities correspond to 1σ errors. The formal 1σ errors in the equivalent width measurements are comparable to the size of the points.
Extended Data Figure 9 Probability distributions for the activity coefficients versus the signal amplitude.
a–n, Marginalized posterior densities of the activity coefficients versus the semi-amplitude of the signal for UVES (a), HARPS pre-2016 (b–f), HARPS PRD campaign (g–k) and the photometric FF′ indices for the PRD campaign only (l–n). Each panel shows equiprobability contours containing 50%, 95% and 99% of the probability density around the mean estimate, and the corresponding standard deviation of the marginalized distribution (1σ) in red. The blue bar shows the zero value of each activity coefficient. Only CF′ is found to be substantially different from zero.
This zipped file contains the time-series used in the paper. All time-series are given as plain ASCII/CSV files (columns separated by commas) and follow the same format. See the README file within the zip folder for details. (ZIP 62 kb)
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Anglada-Escudé, G., Amado, P., Barnes, J. et al. A terrestrial planet candidate in a temperate orbit around Proxima Centauri. Nature 536, 437–440 (2016). https://doi.org/10.1038/nature19106
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