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Fluorescently excited CO emission in the 49 Ceti debris disk spatially resolved by JWST/NIRSpec

Nature Astronomy volume 9, pages 1680–1691 (2025)Cite this article

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Abstract

Debris disks are exosystems thought to arise from collisions among planetesimals. Despite being dust dominated, ALMA has detected reservoirs of CO gas in some debris disks. The origin of this gas is debated, as it could be primordial H2-dominated gas from the parent protoplanetary disk, or it could be released by volatile-rich minor bodies. Here we report JWST/NIRSpec observations of the 49 Ceti debris disk that spatially resolve ro-vibrational CO emission. The CO spectra can be explained by fluorescent excitation from ultraviolet and infrared stellar photons. We show that this technique of resolving fluorescently excited CO is sensitive to small CO masses that could go undetected by ALMA. We compare the CO excitation temperatures derived from our model fitting of the JWST spectra to predictions for an H2-rich and secondary gas model for the system and find that our results do not appear consistent with the H2-rich gas model. Resolving fluorescently excited CO emission opens a door for probing the nature of gas in debris disks and determining if it is long-lived primordial gas or if it is released from volatile-rich minor bodies.

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Fig. 1: Detection of spatially resolved fundamental CO emission.
Fig. 2: PSF-subtracted NIRSpec cube slice at 4.7 μm.
Fig. 3: Fluoresced CO regions and masses.
Fig. 4: Model fits to the NIRSpec spectra.
Fig. 5: Best-fit rotational temperatures of the IR-pumped component as a function of distance from 49 Ceti.

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Data availability

The data used in this work are from GO programme 1563 (PI: C.H.C.) and are publicly available from the Mikulski Archive for Space Telescopes at STScI (https://mast.stsci.edu). The data used for this analysis are available at https://doi.org/10.17909/07pe-y474. The PSF-subtracted data cube and extracted 1D spectra used in the analysis are available via Zenodo at https://doi.org/10.5281/zenodo.16580531 (ref. 60).

Code availability

The code used for performing PSF subtraction on the NIRSpec IFU cubes, generating the CO fluorescence model and fitting the model to the data, which were used in this analysis, is available via Code Ocean at https://doi.org/10.24433/CO.8046058.v1.

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Acknowledgements

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 (STScI), which is operated by the Association of Universities for Research in Astronomy, Inc., under National Aeronautics and Space Administration (NASA) contract NAS 5-03127 for JWST. These observations are associated with GO programme 1563. K.W. is supported by NASA under grant no. 80NSSC22K1752 issued through the Mission Directorate. A.M.H. is supported by the National Science Foundations under grant no. AST-2307920. C.X. is supported by a grant from STScI under contract NAS 5-03127. S.K.B. is supported in part by an STScI Postdoctoral Fellowship. We acknowledge support from ESA through the ESA Space Science Faculty Visitor scheme, funding reference ESA-SCI-E-LE-109. K.W. and C.X.L. acknowledge that support for programme #2053 was provided by NASA through a grant from STScI, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-03127.

Author information

Authors and Affiliations

  1. William H. Miller III Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD, USA

    Kadin Worthen, Christine H. Chen, Chen Xie & Carl Ingebretsen

  2. Space Telescope Science Institute, Baltimore, MD, USA

    Christine H. Chen, Sarah K. Betti, Tracy Beck & Amaya Moro-Martin

  3. Department of Physics and Astronomy, Clemson University, Clemson, SC, USA

    Sean D. Brittain

  4. NSF’s NOIRLab, Tucson, AZ, USA

    Joan R. Najita

  5. Gemini Observatory/NSF’s NOIRLab, Hilo, HI, USA

    Cicero X. Lu

  6. Centro de Astrobiología, INTA-CSIC, Madrid, Spain

    Isabel Rebollido

  7. Department of Astronomy, Van Vleck Observatory, Wesleyan University, Middletown, CT, USA

    A. Meredith Hughes

  8. Johns Hopkins University Applied Physics Laboratory, Laurel, MD, USA

    Carey M. Lisse

  9. Aix Marseille Univ, CNRS, CNES, LAM, Marseille, France

    Elodie Choquet

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Contributions

K.W. led the analysis and wrote the paper. K.W. performed the data reduction, PSF subtraction and CO modelling. C.H.C. is PI for the observing programme and helped with writing, analysis and interpretation. S.D.B., J.R.N., C.X.L. and I.R. assisted with the CO modelling and interpretation of the modelling results. C.X. and S.K.B. helped with the PSF subtraction, throughput correction and spectral extraction. T.B. and C.I. helped with the preprocessing of the data. A.M.H., C.M.L. and A.M.-M. helped with the interpretation of the modelling results and placing them in context with previous works. E.C. helped design the observing programme.

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Correspondence to Kadin Worthen.

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Nature Astronomy thanks Gianni Cataldi and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

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Extended data

Extended Data Fig. 1 Comparison of east and west sides of disk.

a. normalized spectra extracted from a projected distance of 55 au from the east (black) and west (red) sides of the disk. The spectra are normalized to compare their shapes on the opposite sides of the disk. Note that the absolute flux values of the spectra on opposite sides of the disk differ at a less than ~5% ( < 2\(\sigma\)) level. Error bars represent 1 standard deviation. b. same as left but for the projected distance of 80 au. c. same as left but for the projected distance of 100 au.

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Supplementary Information

Supplementary Discussion and Figs. 1–10.

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Worthen, K., Chen, C.H., Brittain, S.D. et al. Fluorescently excited CO emission in the 49 Ceti debris disk spatially resolved by JWST/NIRSpec. Nat Astron 9, 1680–1691 (2025). https://doi.org/10.1038/s41550-025-02664-x

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