Skip to main content

Thank you for visiting nature.com. 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.

  • Article
  • Published:

Thermal emission from the Earth-sized exoplanet TRAPPIST-1 b using JWST

Nature volume 618, pages 39–42 (2023)Cite this article

Subjects

Abstract

The TRAPPIST-1 system is remarkable for its seven planets that are similar in size, mass, density and stellar heating to the rocky planets Venus, Earth and Mars in the Solar System1. All the TRAPPIST-1 planets have been observed with transmission spectroscopy using the Hubble or Spitzer space telescopes, but no atmospheric features have been detected or strongly constrained2,3,4,5. TRAPPIST-1 b is the closest planet to the M-dwarf star of the system, and it receives four times as much radiation as Earth receives from the Sun. This relatively large amount of stellar heating suggests that its thermal emission may be measurable. Here we present photometric secondary eclipse observations of the Earth-sized exoplanet TRAPPIST-1 b using the F1500W filter of the mid-infrared instrument on the James Webb Space Telescope (JWST). We detect the secondary eclipses in five separate observations with 8.7σ confidence when all data are combined. These measurements are most consistent with re-radiation of the incident flux of the TRAPPIST-1 star from only the dayside hemisphere of the planet. The most straightforward interpretation is that there is little or no planetary atmosphere redistributing radiation from the host star and also no detectable atmospheric absorption of carbon dioxide (CO2) or other species.

This is a preview of subscription content, access via your institution

Access options

Buy this article

  • Purchase on SpringerLink
  • Instant access to full article PDF
Buy now

Prices may be subject to local taxes which are calculated during checkout

Fig. 1: Combined TRAPPIST-1 b MIRI F1500W secondary eclipse light curve.
Fig. 2: TRAPPIST-1 b F1500W measured flux and spectral models.

Similar content being viewed by others

Data availability

The data used in this paper are associated with the JWST-GTO-1177 programme (observations 7–11) and will be publicly available from the Mikulski Archive for Space Telescopes (https://mast.stsci.edu) at the end of their one-year exclusive-access periods. Source data are provided with this paper.

Code availability

We used the following codes to process, extract, reduce and analyse the data: STScI JWST calibration pipeline38; Eureka!30; emcee51; starry42; PyMC3 (ref. 43); PySynphot52; and the standard Python libraries numpy53, astropy54 and matplotlib55. These were incorporated into custom Python notebooks for data analysis. These notebooks are available from the corresponding author on request. The notebooks were developed by a NASA employee and cannot be posted publicly until approved by NASA.

References

  1. Gillon, M. et al. Seven temperate terrestrial planets around the nearby ultracool dwarf star TRAPPIST-1. Nature 542, 456–460 (2017).

    Article  ADS  CAS  PubMed  PubMed Central  Google Scholar 

  2. Ducrot, E. et al. The 0.8–4.5 μm broadband transmission spectra of TRAPPIST-1 planets. Astron. J. 156, 218 (2018).

    Article  ADS  CAS  Google Scholar 

  3. de Wit, J. et al. Atmospheric reconnaissance of the habitable-zone Earth-sized planets orbiting TRAPPIST-1. Nat. Astron. 2, 214–219 (2018).

    Article  ADS  Google Scholar 

  4. Zhang, Z., Zhou, Y., Rackham, B. V. & Apai, D. The near-infrared transmission spectra of TRAPPIST-1 planets b, c, d, e, f, and g and stellar contamination in multi-epoch transit spectra. Astron. J. 156, 178 (2018).

    Article  ADS  Google Scholar 

  5. Garcia, L. J. et al. HST/WFC3 transmission spectroscopy of the cold rocky planet TRAPPIST-1h. Astron. Astrophys. 665, A19 (2022).

    Article  CAS  Google Scholar 

  6. Burgasser, A. J. & Mamajek, E. E. On the age of the TRAPPIST-1 system. Astrophys. J. 845, 110 (2017).

    Article  ADS  Google Scholar 

  7. Agol, E. et al. Refining the transit-timing and photometric analysis of TRAPPIST-1: masses, radii, densities, dynamics, and ephemerides. Planet Sci. J. 2, 1 (2021).

    Article  Google Scholar 

  8. Liebert, J. & Gizis, J. E. RI photometry of 2MASS-selected late M and L dwarfs. Publ. Astron. Soc. Pac. 118, 659–670 (2006).

    Article  ADS  Google Scholar 

  9. Roettenbacher, R. M. & Kane, S. R. The stellar activity of TRAPPIST-1 and consequences for the planetary atmospheres. Astrophys. J. 851, 77 (2017).

    Article  ADS  Google Scholar 

  10. Paudel, R. R. et al. K2 ultracool dwarfs survey. III. White light flares are ubiquitous in M6-L0 dwarfs. Astrophys. J. 858, 55 (2018).

    Article  ADS  Google Scholar 

  11. Baraffe, I., Chabrier, G., Allard, F. & Hauschildt, P. H. Evolutionary models for solar metallicity low-mass stars: mass-magnitude relationships and color-magnitude diagrams. Astron. Astrophys. 337, 403–412 (1998).

    ADS  Google Scholar 

  12. Luger, R. & Barnes, R. Extreme water loss and abiotic O2 buildup on planets throughout the habitable zones of M dwarfs. Astrobiology 15, 119–143 (2015).

    Article  ADS  CAS  PubMed  PubMed Central  Google Scholar 

  13. Bolmont, E. et al. Water loss from terrestrial planets orbiting ultracool dwarfs: implications for the planets of TRAPPIST-1. Mon. Not. R. Astron. Soc. 464, 3728–3741 (2017).

    Article  ADS  CAS  Google Scholar 

  14. Tarter, J. C. et al. A reappraisal of the habitability of planets around M dwarf stars. Astrobiology 7, 30–65 (2007).

    Article  ADS  CAS  PubMed  Google Scholar 

  15. Turbet, M. et al. Modeling climate diversity, tidal dynamics and the fate of volatiles on TRAPPIST-1 planets. Astron. Astrophys. 612, A86 (2018).

    Article  Google Scholar 

  16. Tilley, M. A., Segura, A., Meadows, V., Hawley, S. & Davenport, J. Modeling repeated M dwarf flaring at an Earth-like planet in the habitable zone: atmospheric effects for an unmagnetized planet. Astrobiology 19, 64–86 (2019).

    Article  ADS  CAS  PubMed  Google Scholar 

  17. Airapetian, V. S. et al. Impact of space weather on climate and habitability of terrestrial-type exoplanets. Int. J. Astrobiol. 19, 136–194 (2020).

    Article  ADS  Google Scholar 

  18. Grayver, A., Bower, D. J., Saur, J., Dorn, C. & Morris, B. M. Interior heating of rocky exoplanets from stellar flares with application to TRAPPIST-1. Astrophys. J. Lett. 941, L7 (2022).

    Article  ADS  Google Scholar 

  19. Krissansen-Totton, J. & Fortney, J. J. Predictions for observable atmospheres of Trappist-1 planets from a fully coupled atmosphere–interior evolution model. Astrophys. J. 933, 115 (2022).

    Article  ADS  Google Scholar 

  20. Lincowski, A. P. et al. Evolved climates and observational discriminants for the TRAPPIST-1 planetary system. Astrophys. J. 867, 76 (2018).

    Article  ADS  Google Scholar 

  21. Turbet, M. et al. A review of possible planetary atmospheres in the TRAPPIST-1 system. Space Sci. Rev. 216, 100 (2020).

    Article  ADS  CAS  PubMed  PubMed Central  Google Scholar 

  22. Barstow, J. K. & Irwin, P. G. J. Habitable worlds with JWST: transit spectroscopy of the TRAPPIST-1 system? Mon. Not. R. Astron. Soc. 461, L92–L96 (2016).

    Article  ADS  CAS  Google Scholar 

  23. Lustig-Yaeger, J., Meadows, V. S. & Lincowski, A. P. The detectability and characterization of the TRAPPIST-1 exoplanet atmospheres with JWST. Astron. J. 158, 27 (2019).

    Article  ADS  CAS  Google Scholar 

  24. Crossfield, I. J. M. Observations of exoplanet atmospheres. Publ. Astron. Soc. Pac. 127, 941 (2015).

    Article  ADS  Google Scholar 

  25. Koll, D. D. B. A scaling for atmospheric heat redistribution on tidally locked rocky planets. Astrophys. J. 924, 134 (2022).

    Article  ADS  CAS  Google Scholar 

  26. Koll, D. D. B. et al. Identifying candidate atmospheres on rocky M dwarf planets via eclipse photometry. Astrophys. J. 886, 140 (2019).

    Article  ADS  CAS  Google Scholar 

  27. Mansfield, M. et al. Identifying atmospheres on rocky exoplanets through inferred high albedo. Astrophys. J. 886, 141 (2019).

    Article  ADS  CAS  Google Scholar 

  28. Ducrot, E. et al. TRAPPIST-1: global results of the Spitzer exploration science program Red Worlds. Astron. Astrophys. 640, A112 (2020).

    Article  Google Scholar 

  29. Rieke, G. H. et al. The mid-infrared instrument for the James Webb Space Telescope, I: introduction. Publ. Astron. Soc. Pac. 127, 584 (2015).

    Article  ADS  Google Scholar 

  30. Bell, T. et al. Eureka!: an end-to-end pipeline for JWST time-series observations. J. Open Source Softw. 7, 4503 (2022).

    Article  ADS  Google Scholar 

  31. Husser, T. O. et al. A new extensive library of PHOENIX stellar atmospheres and synthetic spectra. Astron. Astrophys. 553, A6 (2013).

    Article  Google Scholar 

  32. Cowan, N. B. & Agol, E. A model for thermal phase variations of circular and eccentric exoplanets. Astrophys. J. 726, 82 (2011).

    Article  ADS  Google Scholar 

  33. University of Washington. VPL Spectral Explorer (2018); https://live-vpl-test.pantheonsite.io/models/vpl-spectral-explorer/.

  34. Delrez, L. et al. Early 2017 observations of TRAPPIST-1 with Spitzer. Mon. Not. R. Astron. Soc. 475, 3577–3597 (2018).

    Article  ADS  Google Scholar 

  35. Kreidberg, L. et al. Absence of a thick atmosphere on the terrestrial exoplanet LHS 3844b. Nature 573, 87–90 (2019).

    Article  ADS  CAS  PubMed  Google Scholar 

  36. Lightsey, P. A. & Wei, Z. James Webb Space Telescope stray light performance status update. In Proc. SPIE 8442, Space Telescopes and Instrumentation 2012: Optical, Infrared, and Millimeter Wave 84423B (SPIE, 2012).

  37. Rigby, J. R. et al. How dark the sky: the JWST backgrounds. Publ. Astron. Soc. Pac. 135, 048002 (2023).

  38. JWST Calibration Pipeline Developers. JWST: Python library for science observations from the James Webb Space Telescope. GitHub https://github.com/spacetelescope/jwst (2022).

  39. CRDS Developers. CRDS: calibration reference data system for HST and JWST. GitHub https://github.com/spacetelescope/crds (2022).

  40. Rigby, J. et al. The science performance of JWST as characterized in commissioning. Publ. Astron. Soc. Pac. 135, 048001 (2023).

  41. Guillard, P. et al. MIRI point spread functions: radial and encircled energy profiles (2023); https://jwst-docs.stsci.edu/jwst-mid-infrared-instrument/miri-performance/miri-point-spread-functions#MIRIPointSpreadFunctions-Radialandencircledenergyprofiles.

  42. Luger, R. et al. rodluger/starry: v1.2.0. Zenodo https://zenodo.org/record/5567790/export/csl (2021).

  43. Salvatier, J., Wiecki, T. V. & Fonnesbeck, C. Probabilistic programming in Python using PyMC3. PeerJ Comput. Sci. 2, e55 (2016).

    Article  Google Scholar 

  44. Gelman, A. & Rubin, D. B. Inference from iterative simulation using multiple sequences. Stat. Sci. 7, 457–472 (1992).

    Article  MATH  Google Scholar 

  45. Allan, D. W. Statistics of atomic frequency standards. IEEE Proc. 54, 221–230 (1966).

    Article  ADS  Google Scholar 

  46. Gillon, M. et al. The Spitzer search for the transits of HARPS low-mass planets. Astron. Astrophys. 518, A25 (2010).

    Article  Google Scholar 

  47. Gillon, M. et al. The TRAPPIST survey of southern transiting planets. I. Thirty eclipses of the ultra-short period planet WASP-43 b. Astron. Astrophys. 542, A4 (2012).

    Article  Google Scholar 

  48. Gillon, M. et al. Search for a habitable terrestrial planet transiting the nearby red dwarf GJ 1214. Astron. Astrophys. 563, A21 (2014).

    Article  Google Scholar 

  49. Mandel, K. & Agol, E. Analytic light curves for planetary transit searches. Astrophys. J. Lett. 580, L171–L175 (2002).

    Article  ADS  Google Scholar 

  50. Bouwman, J. et al. Spectroscopic time series performance of the mid-infrared instrument on the JWST. Publ. Astron. Soc. Pac. 135, 038002 (2023).

  51. Foreman-Mackey, D., Hogg, D. W., Lang, D. & Goodman, J. emcee: the MCMC hammer. Publ. Astron. Soc. Pac. 125, 306 (2013).

    Article  ADS  Google Scholar 

  52. Lim, P. L., Diaz, R. I. & Laidler, V. PySynphot user’s guide (2015); https://pysynphot.readthedocs.io/en/latest/.

  53. Harris, C. R. et al. Array programming with NumPy. Nature 585, 357–362 (2020).

    Article  ADS  CAS  PubMed  PubMed Central  Google Scholar 

  54. The Astropy Collaboration. The Astropy project: sustaining and growing a community-oriented open-source project and the latest major release (v5.0) of the core package. Astrophys. J. 935, 167 (2022).

    Article  ADS  Google Scholar 

  55. Hunter, J. D. Matplotlib: a 2D graphics environment. Comput. Sci. Eng. 9, 90–95 (2007).

    Article  Google Scholar 

Download references

Acknowledgements

We thank E. Schlawin, M. Gillon, V. Parmentier and E. Rauscher for discussions and L. Kreidberg for comments that helped to improve the manuscript. This work is based on observations made with the NASA/ESA/CSA JWST. The data were obtained from the Mikulski Archive for Space Telescopes at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy under NASA contract NAS 5-03127 for JWST. These observations are associated with the JWST-GTO-1177 programme. We thank the MIRI instrument team and the many other people who contributed to the success of JWST. T.P.G. and T.J.B. acknowledge funding support from the NASA Next Generation Space Telescope Flight Investigations programme (now JWST) by WBS 411672.07.04.01.02. This material is based on work supported by NASA Interdisciplinary Consortia for Astrobiology Research (NNH19ZDA001N-ICAR) under award number 19-ICAR19_2-0041 (to J.J.F.) and NASA WBS 811073.02.12.04.71 (to T.P.G.). P.-O.L. acknowledges funding support from CNES. E.D. acknowledges support from the EU Horizon 2020 research and innovation programme in the context of the Marie Skłodowska-Curie subvention 945298. E.D. is a Paris Region Fellow and is funded by the Marie Skłodowska-Curie Actions.

Author information

Authors and Affiliations

  1. Space Science and Astrobiology Division, NASA Ames Research Center, Moffett Field, CA, USA

    Thomas P. Greene & Taylor J. Bell

  2. Bay Area Environmental Research Institute, NASA Ames Research Center, Moffett Field, CA, USA

    Taylor J. Bell

  3. Université Paris-Saclay, Université Paris-Cité, CEA, CNRS, Gif-sur-Yvette, France

    Elsa Ducrot, Achrène Dyrek & Pierre-Olivier Lagage

  4. Department of Astronomy and Astrophysics, University of California, Santa Cruz, Santa Cruz, CA, USA

    Jonathan J. Fortney

Authors
  1. Thomas P. Greene
    View author publications

    You can also search for this author in PubMed Google Scholar

  2. Taylor J. Bell
    View author publications

    You can also search for this author in PubMed Google Scholar

  3. Elsa Ducrot
    View author publications

    You can also search for this author in PubMed Google Scholar

  4. Achrène Dyrek
    View author publications

    You can also search for this author in PubMed Google Scholar

  5. Pierre-Olivier Lagage
    View author publications

    You can also search for this author in PubMed Google Scholar

  6. Jonathan J. Fortney
    View author publications

    You can also search for this author in PubMed Google Scholar

Contributions

T.P.G. provided the programme leadership, devised the observational programme, led setting the observation parameters, contributed to the data analysis, led the interpretation of the results and led the writing of the manuscript. T.J.B. verified the observing parameters and led the data analysis. E.D. checked and contributed to the observing parameters, data analysis and interpretation of the results. A.D. contributed to the data reduction. P.-O.L. contributed to the design of the observational programme and setting the observing parameters, commented on the draft manuscript and contributed to the data analysis. J.J.F. contributed to the design of the observational programme, provided information for the paper and helped to interpret the results.

Corresponding author

Correspondence to Thomas P. Greene.

Ethics declarations

Competing interests

The authors declare no competing interests.

Peer review

Peer review information

Nature thanks L. Kreidberg and the other, anonymous, reviewer(s) for their contribution to the peer review of this work. Peer reviewer reports are available.

Additional information

Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Extended data figures and tables

Extended Data Fig. 1 Light curves of individual observations and the Joint Fit #1 models.

a. The raw light curves from each of our five visits normalized by their median value are shown in color, while the fitted model from Joint Fit #1 including systematic noise is shown using a black line. The date in UT of each visit is indicated by the y-axis labels. Each visit did not start at the same orbital phase, so the apparent movement in the eclipse time is simply caused by when the observations began. b. The same data and model from each visit after the removal of systematic noise. Overplotted are data binned at a cadence of 9.7 minutes (14 integrations) to more clearly visualize the detection of the eclipse in each visit. All error bars show 1σ uncertainties in both panels.

Source data

Extended Data Table 1 Mid-eclipse times
Full size table

Supplementary information

Source data

Rights and permissions

Reprints and permissions

About this article

Check for updates. Verify currency and authenticity via CrossMark

Cite this article

Greene, T.P., Bell, T.J., Ducrot, E. et al. Thermal emission from the Earth-sized exoplanet TRAPPIST-1 b using JWST. Nature 618, 39–42 (2023). https://doi.org/10.1038/s41586-023-05951-7

Download citation

  • Received:

  • Accepted:

  • Published:

  • Issue Date:

  • DOI: https://doi.org/10.1038/s41586-023-05951-7

This article is cited by

Comments

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.

Search

Advanced search

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