Skip to main content

Thank you for visiting You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

The changing phases of extrasolar planet CoRoT-1b


Hot Jupiters are a class of extrasolar planet that orbit their parent stars at very short distances. They are expected to be tidally locked, which can lead to a large temperature difference between their daysides and nightsides. Infrared observations of eclipsing systems have yielded dayside temperatures for a number of transiting planets1,2,3,4,5. The day–night contrast of the transiting extrasolar planet HD 189733b was ‘mapped’ using infrared observations6,7. It is expected that the contrast between the daysides and nightsides of hot Jupiters is much higher at visual wavelengths, shorter than that of the peak emission, and could be further enhanced by reflected stellar light. Here we report the analysis of optical photometric data8 obtained over 36 planetary orbits of the transiting hot Jupiter CoRoT-1b. The data are consistent with the nightside hemisphere of the planet being entirely black, with the dayside flux dominating the optical phase curve. This means that at optical wavelengths the planet’s phase variation is just as we see it for the interior planets in the Solar System. The data allow for only a small fraction of reflected light, corresponding to a geometric albedo of <0.20.

This is a preview of subscription content

Access options

Buy article

Get time limited or full article access on ReadCube.


All prices are NET prices.

Figure 1: Optical phase variation for CoRoT-1b centred on the planetary eclipse.
Figure 2: The optical planet–star contrast compared with models.


  1. Charbonneau, D. et al. Detection of thermal emission from an extrasolar planet. Astrophys. J. 626, 523–529 (2005)

    CAS  ADS  Article  Google Scholar 

  2. Deming, D., Seager, S., Richardson, L. J. & Harrington, J. Infrared radiation from an extrasolar planet. Nature 434, 740–743 (2005)

    CAS  ADS  Article  Google Scholar 

  3. Harrington, J., Luszcz, S., Seager, S., Deming, D. & Richardson, L. The hottest planet. Nature 447, 691–693 (2007)

    CAS  ADS  Article  Google Scholar 

  4. Sing, D. K. & Lopez-Morales, M. Ground-based secondary eclipse detection of the very-hot Jupiter OGLE-TR-56b. Astron. Astrophys. 493, L31–L34 (2009)

    ADS  Article  Google Scholar 

  5. de Mooij, E. J. W. & Snellen, I. A. G. Ground-based K-band detection of thermal emission from the exoplanet TrES-3b. Astron. Astrophys. 493, L35–L38 (2009)

    ADS  Article  Google Scholar 

  6. Knutson, H. A. et al. A map of the day–night contrast of the extrasolar planet HD 189733b. Nature 447, 183–186 (2007)

    CAS  ADS  Article  Google Scholar 

  7. Knutson, H. et al. Multiwavelength constraints on the day-night circulation patterns of HD 189733b. Astrophys. J. 690, 822–836 (2009)

    CAS  ADS  Article  Google Scholar 

  8. Auvergne, M., Bodin, P., Boisnard, L., Buey, J., Chaintreuil, S. & CoRoT team The CoRoT satellite in flight: description and performance. Astron. Astrophys. (in the press); preprint at 〈〉 (2009)

  9. Barge, P. et al. Transiting exoplanets from the CoRoT space mission. I. CoRoT-Exo-1b: a low-density short-period planet around a G0V star. Astron. Astrophys. 482, L17–L20 (2008)

    ADS  Article  Google Scholar 

  10. Samadi, R. et al. Extraction of the photometric information: corrections. Preprint at 〈〉 (2007)

  11. Kurucz, R. ATLAS9 Stellar Atmosphere Programs and 2 km/s Grid. (Kurucz CD-ROM No. 13, Smithsonian Astrophysical Observatory, 1993)

    Google Scholar 

  12. Fortney, J., Lodders, K., Marley, M. & Freedman, R. A unified theory for the atmospheres of the hot and very hot Jupiters: two classes of irradiated atmospheres. Astrophys. J. 678, 1419–1435 (2008)

    CAS  ADS  Article  Google Scholar 

  13. Cooper, C. & Showman, A. Dynamic meteorology at the photosphere of HD 209458b. Astrophys. J. 629, L45–L48 (2005)

    CAS  ADS  Article  Google Scholar 

  14. Showman, A. et al. Atmospheric circulation of hot Jupiters: coupled radiative-dynamical general circulation model simulations of HD 189733b and HD 209458b. Astrophys. J. (submitted); preprint at 〈〉 (2008)

  15. Burrows, A., Hubeny, I., Budaj, J., Knutson, H. & Charbonneau, D. Theoretical spectral models of the planet HD 209458b with a thermal inversion and water emission bands. Astrophys. J. 668, L171–L174 (2007)

    CAS  ADS  Article  Google Scholar 

  16. Grillmair, C. et al. Strong water absorption in the dayside emission spectrum of the planet HD 189733b. Nature 456, 767–769 (2008)

    CAS  ADS  Article  Google Scholar 

  17. Knutson, H., Charbonneau, D., Burrows, A., O’Donovan, F. & Mandushev, G. Detection of a temperature inversion in the broadband infrared emission spectrum of TrES-4. Astrophys. J. 691, 866–874 (2009)

    ADS  Article  Google Scholar 

  18. Cowan, N., Agol, E. & Charbonneau, D. Hot nights on extrasolar planets: mid-infrared phase variations of hot Jupiters. Mon. Not. R. Astron. Soc. 379, 641–646 (2007)

    CAS  ADS  Article  Google Scholar 

  19. Knutson, H., Charbonneau, D. & Allen, L. The 3.6–8.0 μm broadband emission spectrum of HD 209458b: evidence for an atmospheric temperature inversion. Astrophys. J. 673, 526–531 (2008)

    CAS  ADS  Article  Google Scholar 

  20. Harrington, J. et al. The phase-dependent infrared brightness of the extrasolar planet υ Andromedae b. Science 314, 623–626 (2006)

    CAS  ADS  Article  Google Scholar 

  21. Burrows, A., Budaj, J. & Hubeny, I. Theoretical spectra and light curves of close-in extrasolar giant planets and comparison with data. Astrophys. J. 678, 1436–1457 (2008)

    CAS  ADS  Article  Google Scholar 

  22. Collier Cameron, A., Horne, K., Penny, A. & Leigh, C. A search for starlight reflected from υ And’s innermost planet. Mon. Not. R. Astron. Soc. 330, 187–204 (2002)

    ADS  Article  Google Scholar 

  23. Leigh, C. et al. A search for starlight reflected from HD 75289b. Mon. Not. R. Astron. Soc. 346, L16–L20 (2003)

    ADS  Article  Google Scholar 

  24. Leigh, C., Collier Cameron, A., Horne, K., Penny, A. & James, D. A. new upper limit on the reflected starlight from τ Bootis b. Mon. Not. R. Astron. Soc. 344, 1271–1282 (2003)

    ADS  Article  Google Scholar 

  25. Rowe, J. F. et al. The very low albedo of an extrasolar planet: MOST space-based photometry of HD 209458. Astrophys. J. 689, 1345–1353 (2008)

    ADS  Article  Google Scholar 

  26. Cox, A. N. in Allen’s Astrophysical Quantities 4th edn (ed. Cox, A. N.) Ch. 1 (Athlone, 2000)

    Google Scholar 

  27. Seager, S., Whitney, B. A. & Sasselov, D. D. Photometric light curves and polarization of close-in extrasolar giant planets. Astrophys. J. 540, 504–520 (2000)

    CAS  ADS  Article  Google Scholar 

  28. Green, D., Matthews, J., Seager, S. & Kuschnig, R. Scattered light from close-in extrasolar planets: prospects of detection with the MOST satellite. Astrophys. J. 597, 590–601 (2003)

    ADS  Article  Google Scholar 

  29. Hood, B., Wood, K., Seager, S. & Collier Cameron, A. Reflected light from three dimensional exoplanetary atmospheres and simulations of HD 209458b. Mon. Not. R. Astron. Soc. 389, 257–269 (2008)

    CAS  ADS  Article  Google Scholar 

Download references


We thank the CoRoT team for making the CoRoT data, which forms the basis of this study, publicly available in a high-quality and comprehensible way. The CoRoT space mission, launched on 27 December 2006, was developed and is operated by the Centre National D’Études Spatial, with participation of the science programmes of the European Space Agency, the European Space Research and Technology Centre and the Research and Scientific Support Department, Austria, Belgium, Brazil, Germany and Spain. We thank R. Le Poole for discussions.

Author information

Authors and Affiliations


Corresponding author

Correspondence to Ignas A. G. Snellen.

Supplementary information

Supplementary Information

This file contains Supplementary Methods and Data, Supplementary References Supplementary Table 1and Supplementary Figures 1-11 with Legends. (PDF 522 kb)

PowerPoint slides

Rights and permissions

Reprints and Permissions

About this article

Cite this article

Snellen, I., de Mooij, E. & Albrecht, S. The changing phases of extrasolar planet CoRoT-1b. Nature 459, 543–545 (2009).

Download citation

  • Received:

  • Accepted:

  • Issue Date:

  • DOI:

Further reading


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.


Quick links

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing