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Infrared radiation from an extrasolar planet


A class of extrasolar giant planets—the so-called ‘hot Jupiters’ (ref. 1)—orbit within 0.05 au of their primary stars (1 au is the Sun–Earth distance). These planets should be hot and so emit detectable infrared radiation2. The planet HD 209458b (refs 3, 4) is an ideal candidate for the detection and characterization of this infrared light because it is eclipsed by the star. This planet has an anomalously large radius (1.35 times that of Jupiter5), which may be the result of ongoing tidal dissipation6, but this explanation requires a non-zero orbital eccentricity ( 0.03; refs 6, 7), maintained by interaction with a hypothetical second planet. Here we report detection of infrared (24 µm) radiation from HD 209458b, by observing the decrement in flux during secondary eclipse, when the planet passes behind the star. The planet's 24-µm flux is 55 ± 10 µJy (1σ), with a brightness temperature of 1,130 ± 150 K, confirming the predicted heating by stellar irradiation2,8. The secondary eclipse occurs at the midpoint between transits of the planet in front of the star (to within ± 7 min, 1σ), which means that a dynamically significant orbital eccentricity is unlikely.

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Figure 1: Observations showing our detection of the secondary eclipse in HD 209458.
Figure 2: Amplitude of the secondary eclipse versus assumed central phase, with confidence intervals for both.
Figure 3: Flux from a model atmosphere shown in comparison to our measured infrared flux at 24 µm.


  1. Collier-Cameron, A. Extrasolar planets: what are hot Jupiters made of? Astron. Geophys. 43, 421–425 (2002)

    Google Scholar 

  2. Seager, S. & Sasselov, D. D. Extrasolar giant planets under strong stellar irradiation. Astrophys. J. 502, L157–L161 (1998)

    Article  ADS  CAS  Google Scholar 

  3. Charbonneau, D., Brown, T. M., Latham, D. W. & Mayor, M. Detection of planetary transits across a sun-like star. Astrophys. J. 529, L45–L48 (2000)

    Article  ADS  CAS  Google Scholar 

  4. Henry, G. W., Marcy, G. W., Butler, R. P. & Vogt, S. S. A transiting “51 Peg-like” planet. Astrophys. J. 529, L41–L44 (2000)

    Article  ADS  CAS  Google Scholar 

  5. Brown, T. M., Charbonneau, D., Gilliland, R. L., Noyes, R. W. & Burrows, A. Hubble Space Telescope time-series photometry of the transiting planet of HD 209458. Astrophys. J. 552, 699–709 (2001)

    Article  ADS  Google Scholar 

  6. Bodenheimer, P., Lin, D. N. C. & Mardling, R. A. On the tidal inflation of short-period extrasolar planets. Astrophys. J. 548, 466–472 (2001)

    Article  ADS  Google Scholar 

  7. Laughlin, G. et al. A comparison of observationally determined radii with theoretical radius predictions for short-period transiting extrasolar planets. Astrophys. J. (in the press)

  8. Burrows, A., Sudarsky, D. & Hubeny, I. in The Search for Other Worlds: Proc. 14th Annu. Astrophys. Conf. in Maryland (eds Holt, S. & Deming, D.) Vol. 713, 143–150 (American Institute of Physics, Melville, New York, 2003)

    Google Scholar 

  9. Werner, M. W. et al. The Spitzer Space Telescope mission. Astrophys. J. Suppl. 154, 1–9 (2004)

    Article  ADS  Google Scholar 

  10. Rieke, G. H. et al. The Multiband Imaging Photometer for Spitzer (MIPS). Astrophys. J. Suppl. 154, 25–29 (2004)

    Article  ADS  Google Scholar 

  11. Beichman, C. A. et al. Planets and IR excesses: preliminary results from a Spitzer MIPS survey of solar-type stars. Astrophys. J. (in the press)

  12. Ribas, A. H., Solano, E., Masana, E. & Gimenez, A. Effective temperatures and radii of planet-hosting stars from IR photometry. Astron. Astrophys. 411, L501–L504 (2003)

    Article  ADS  CAS  Google Scholar 

  13. Perryman, M. A. C. (ed.) The Hipparcos and Tycho Catalogues (ESA SP-1200, European Space Agency, Noordwijk, 1997).

  14. Kurucz, R. Solar Abundance Model Atmospheres for 0, 1, 2, 4, and 8 km/s CD-ROM 19 (Smithsonian Astrophysical Observatory, Cambridge, Massachusetts, 1994).

  15. Horne, K. An optimal extraction algorithm for CCD spectrososcopy. Publ. Astron. Soc. Pacif. 98, 609–617 (1986)

    Article  ADS  CAS  Google Scholar 

  16. Krist, J. in Astronomical Data Analysis Software and Systems IV (eds Shaw, R. A., Payne, H. E. & Hayes, J. J. E.) Vol. 77, 349–352 (Astronomical Society of the Pacific, San Francisco, 1995)

    Google Scholar 

  17. Gordon, K. D. Reduction algorithms for the Multiband Imaging Photometer for SIRTF. Publ. Astron. Soc. Pacif. (in the press)

  18. Rieke, G. H. et al. in Proc. SPIE: Optical, Infrared, and Millimeter Space Telescopes (ed. Mather, J. C.) Vol. 5487, 50–61 (SPIE, Bellingham, Washington, 2004)

    Book  Google Scholar 

  19. Kelsall, T. et al. The COBE Diffuse Infrared Background Experiment (DIRBE) search for the cosmic infrared background. II. Model of the interplanetary dust cloud. Astrophys. J. 508, 44–73 (1998)

    Article  ADS  Google Scholar 

  20. Wittenmyer, R. A. The Orbital Ephemeris of HD 209458b. Master's thesis, San Diego State Univ. (2003)

    Google Scholar 

  21. Goukenleuque, C., Bezard, B., Joguet, B., Lellouch, E. & Freedman, R. A radiative equilibrium model of 51 Peg b. Icarus 143, 308–323 (2000)

    Article  ADS  CAS  Google Scholar 

  22. 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)

    Article  ADS  CAS  Google Scholar 

  23. Barman, T. S., Hauschildt, P. H. & Allard, F. Irradiated planets. Astrophys. J. 556, 885–895 (2001)

    Article  ADS  CAS  Google Scholar 

  24. Sudarsky, D., Burrows, A. & Hubeny, I. Theoretical spectra and atmospheres of extrasolar giant planets. Astrophys. J. 588, 1121–1148 (2003)

    Article  ADS  CAS  Google Scholar 

  25. Charbonneau, D. in Scientific Frontiers in Research on Extrasolar Planets (eds Deming, D. & Seager, S.) Vol. 294, 449–456 (Astronomical Society of the Pacific, San Francisco, 2003)

    Google Scholar 

  26. Press, W. H., Teukolsky, S. A., Vettering, W. T. & Flannery, B. P. Numerical recipes in C 2nd edn (Cambridge Univ. Press, Cambridge, 1992)

    Google Scholar 

  27. Alonso, R. et al. TrES-1, the transiting planet of a bright K0V star. Astrophys. J. 613, L153–L156 (2004)

    Article  ADS  CAS  Google Scholar 

  28. Charbonneau, D. et al. Detection of thermal emission from an extrasolar planet. Astrophys. J. (in the press)

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We thank G. Laughlin for communicating the latest orbital eccentricity solutions from the Doppler data and for his evaluation of their status. We acknowledge informative conversations with D. Charbonneau, G. Marcy, B. Hansen, K. Menou and J. Cho. 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 contract to NASA. Support for this work was provided directly by NASA, and by its Origins of Solar Systems programme and Astrobiology Institute. We thank all the personnel of the Spitzer telescope and the MIPS instrument, who ultimately made these measurements possible. L.J.R. is a National Research Council Associate at NASA's Goddard Space Flight Center.

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Correspondence to Drake Deming.

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Supplementary information

Supplementary Figure S1

Sample flat-fielded and flux-calibrated MIPS image of HD 209458 produced by the Spitzer S11.0 data processing pipeline. (PDF 95 kb)

Supplementary Figure S2

A tabulation of the temporal deviations in normalized intensity for all detector pixels not containing the star, with Fourier power spectra, for a sample data block. Shows gaussian white noise properties. (PDF 70 kb)

Supplementary Figure S3

A tabulation of the temporal deviations in normalized intensity for all detector pixels within ± 10 pixels of the the star, for a sample data block. Shows gaussian property of the noise. (PDF 47 kb)

Supplementary Figure Legends

Legends to accompany Supplementary Figures S1-S3. (DOC 23 kb)

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Deming, D., Seager, S., Richardson, L. et al. Infrared radiation from an extrasolar planet. Nature 434, 740–743 (2005).

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