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A sub-Mercury-sized exoplanet


An Erratum to this article was published on 03 April 2013


Since the discovery of the first exoplanets1,2, it has been known that other planetary systems can look quite unlike our own3. Until fairly recently, we have been able to probe only the upper range of the planet size distribution4,5, and, since last year, to detect planets that are the size of Earth6 or somewhat smaller7. Hitherto, no planets have been found that are smaller than those we see in the Solar System. Here we report a planet significantly smaller than Mercury8. This tiny planet is the innermost of three that orbit the Sun-like host star, which we have designated Kepler-37. Owing to its extremely small size, similar to that of the Moon, and highly irradiated surface, the planet, Kepler-37b, is probably rocky with no atmosphere or water, similar to Mercury.

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Figure 1: The transit light curves for the planets orbiting Kepler-37.

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Kepler was competitively selected as the tenth Discovery mission. Funding for this mission is provided by NASA’s Science Mission Directorate. Some of this work is based 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. Support for this work was provided by NASA through an award issued by JPL/Caltech. Kepler flux time series data presented in this paper are available from the Mikulski Archive for Space Telescopes (MAST) at the Space Telescope Science Institute (STScI). Funding for the Stellar Astrophysics Centre is provided by The Danish National Research Foundation. The research is supported by the ASTERISK project funded by the European Research Council. E.A. acknowledges support through an NSF Career grant. D.H. is supported by an appointment to the NASA Postdoctoral Program at Ames Research Center.

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Authors and Affiliations



T.B. led the work, performed the Markov chain Monte Carlo transit modelling and wrote the manuscript. J.F.R. discovered Kepler-37b and Kepler-37c and performed the initial analysis of the light curve. J.J.L. provided guidance on the false-positive probability and contributed to the manuscript. D.H. discovered the solar-like oscillations and led the asteroseismic analysis. F.F. led the BLENDER analysis. S.T.B. performed pixel-level centroid analysis. W.J.C. led the asteroseismic modelling effort. J.-M.D. and D. Charbonneau obtained and analysed the Spitzer observations and wrote the section in Supplementary Information based on these data. E.D.L. calculated the planetary composition constraints. G.W.M. obtained HIRES spectra (Supplementary Information, sections 1 and 3) and performed the cross-correlation function calculation. F.M. developed a model for assessing false-positive probabilities based on colours. D.R. calculated the coplanarity boost used in BLENDER. G.T. developed the BLENDER technique and was involved in the corresponding analysis. E.R.A. and A.K.D. obtained and analysed the adaptive optics images from the MMT. E.A. identified additional transiting planet candidates in the Kepler-37 system. D.B. and J.L.-B. obtained and analysed the lucky imaging data (Supplementary Information, section 4). S.B., T.R.B., J.C.-D., Y.E., R.H., S.H., C.K., S.D.K., H.K., M.N.L., M.L., T.S.M., A.M. and D.S. were involved in the asteroseismic analysis and modelling. L.A.B. analysed the TrES and HIRES spectra using SPC (Supplementary Information, section 1). J.L.C, M.R.H., J.M.J., T.C.K., J.L., R.L.M, E.V.Q., J.C.S., M.S. and S.E.T. were involved in the target management, processing, analysis and dissemination of Kepler data. D. Ciardi, M.E., E.H. and S.B.H. recorded and analysed the high-contrast imaging data. D.A.F. analysed HIRES spectra using SME. J.C.G. developed the Kepler photometer electronics, built Keplercam for the KIC and follow-up spectral observations, and developed the TRES echelle spectrograph at SAO for follow-up observations. E.B.F. contributed to the analysis of transit times and eccentricities. J.J.F. assisted in modelling the structure and evolution of the planets. C.E.H. assisted in running BLENDER on the NASA Pleiades supercomputer. A.W.H. and H.I. obtained and analysed the HIRES radial velocity data. R.H. manages the Kepler project. D.W.L. obtained TrES spectra.

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Correspondence to Thomas Barclay or Jason F. Rowe.

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The authors declare no competing financial interests.

Supplementary information

Supplementary Information

This file contains Supplementary Text and Data 1-8, Supplementary Figures 1-4, Supplementary Table 1 and additional references. (PDF 1676 kb)

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Barclay, T., Rowe, J., Lissauer, J. et al. A sub-Mercury-sized exoplanet. Nature 494, 452–454 (2013).

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