Clouds in the atmosphere of the super-Earth exoplanet GJ 1214b (original) (raw)

Nature volume 505, pages 69–72 (2014)Cite this article

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Abstract

Recent surveys have revealed that planets intermediate in size between Earth and Neptune (‘super-Earths’) are among the most common planets in the Galaxy1,2,3. Atmospheric studies are the next step towards developing a comprehensive understanding of this new class of object4,5,6. Much effort has been focused on using transmission spectroscopy to characterize the atmosphere of the super-Earth archetype GJ 1214b (refs 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17), but previous observations did not have sufficient precision to distinguish between two interpretations for the atmosphere. The planet’s atmosphere could be dominated by relatively heavy molecules, such as water (for example, a 100 per cent water vapour composition), or it could contain high-altitude clouds that obscure its lower layers. Here we report a measurement of the transmission spectrum of GJ 1214b at near-infrared wavelengths that definitively resolves this ambiguity. The data, obtained with the Hubble Space Telescope, are sufficiently precise to detect absorption features from a high mean-molecular-mass atmosphere. The observed spectrum, however, is featureless. We rule out cloud-free atmospheric models with compositions dominated by water, methane, carbon monoxide, nitrogen or carbon dioxide at greater than 5_σ_ confidence. The planet’s atmosphere must contain clouds to be consistent with the data.

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Acknowledgements

This work is based on observations made with the NASA/ESA Hubble Space Telescope that were obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract number NAS 5-26555. These observations are associated with program GO-13021. Support for this work was provided by NASA through a grant from the Space Telescope Science Institute, the National Science Foundation through a Graduate Research Fellowship (to L.K.), the Alfred P. Sloan Foundation through a Sloan Research Fellowship (to J.L.B.), NASA through a Sagan Fellowship (to J.-M.D.), and the European Research Council (for D.H. under the European Community's Seventh Framework Programme, FP7/2007-2013 Grant Agreement number 247060).

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Authors and Affiliations

  1. Department of Astronomy and Astrophysics, University of Chicago, Chicago, 60637, Illinois, USA
    Laura Kreidberg, Jacob L. Bean, Kevin B. Stevenson & Andreas Seifahrt
  2. Department of Astrophysical and Planetary Sciences, CASA, University of Colorado, Boulder, 80309, Colorado, USA
    Jean-Michel Désert
  3. Department of Astronomy, California Institute of Technology, Pasadena, 91101, California, USA
    Jean-Michel Désert
  4. Department of Physics, Massachusetts Institute of Technology, Cambridge, 02139, Massachusetts, USA
    Björn Benneke & Sara Seager
  5. Department of Astronomy, University of Maryland, College Park, 20742, Maryland, USA
    Drake Deming
  6. Department of Astronomy, Harvard University, Cambridge, 02138, Massachusetts, USA
    Zachory Berta-Thompson
  7. MIT Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, Cambridge, 02139, Massachusetts, USA
    Zachory Berta-Thompson
  8. Centre de Recherche Astrophysique de Lyon, 69364 Lyon, France ,
    Derek Homeier

Authors

  1. Laura Kreidberg
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  2. Jacob L. Bean
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  3. Jean-Michel Désert
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  4. Björn Benneke
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  5. Drake Deming
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  6. Kevin B. Stevenson
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  7. Sara Seager
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  8. Zachory Berta-Thompson
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  9. Andreas Seifahrt
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  10. Derek Homeier
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Contributions

L.K. led the data analysis (with contributions from J.L.B., D.D., K.B.S. and A.S.). J.L.B and J.-M.D. conceived the project and wrote the telescope time proposal (with contributions from B.B., D.D., S.S. and Z.B.-T.). L.K., J.L.B., J.-M.D., D.D. and Z.B.-T. planned the observations. B.B. and S.S. developed and performed the theoretical modelling. D.H. calculated the theoretical stellar limb darkening. J.L.B. led the overall direction of the project. L.K., J.L.B., J.-M.D. and B.B. wrote the paper. All authors discussed the results and commented on the manuscript.

Corresponding author

Correspondence toLaura Kreidberg.

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The authors declare no competing financial interests.

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The data used in this work can be accessed at the NASA Mikulski Archive for Space Telescopes (http://archive.stsci.edu).

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Kreidberg, L., Bean, J., Désert, JM. et al. Clouds in the atmosphere of the super-Earth exoplanet GJ 1214b.Nature 505, 69–72 (2014). https://doi.org/10.1038/nature12888

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Editorial Summary

A tale of two planets

Two papers in this issue of Nature report Hubble Space Telescope observations of two separate sub-Jupiter-sized extrasolar planets. Heather Knutson et al. observed four transits of the Neptune-mass planet GJ 436b and Laura Kreidberg et al. observed 15 transits of the smaller 'super-Earth' GJ 1214b. The transmission spectra of starlight passing through the atmospheres of these planets should give a good indication of the nature of their respective atmospheres, and for both planets the spectra obtained from Hubble's Wide Field Camera 3 are virtually featureless. Knutson et al. argue that their data are consistent with either a high cloud deck at pressures of 0.1–10 mbar or a hydrogen-poor atmosphere on GJ 436b. Kreidberg et al. conclude that their near-infrared spectra are consistent with the presence of high-altitude clouds that obscure the lower layers of GJ 1214b.

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