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  • Matters Arising
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Concerning the possible exomoons around Kepler-1625 b and Kepler-1708 b

Nature Astronomy volume 9, pages 795–798 (2025)Cite this article

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The Original Article was published on 07 December 2023

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arising from Heller, R. & Hippke, M. Nature Astronomy https://doi.org/10.1038/s41550-023-02148-w (2024)

Recently, Heller and Hippke1 argued that the exomoon candidates Kepler-1625 b-i and Kepler-1708 b-i were allegedly ‘refuted’. In this Matters Arising, we address these claims. For Kepler-1625 b-i, we show that their Hubble light curve is identical to that previously published by the same lead author2, in which the moon-like dip was recovered. Indeed, our fits of their data again recover this dip with improved residuals compared with the work of Heller and Hippke1. Their fits therefore somehow missed this deeper likelihood maximum, producing apparently unconverged posteriors. Consequently, their best-fitting moon is the same radius as the planet, Kepler-1625 b-i, a radically different signal from that originally claimed3. The authors then inject this solution into the Kepler data and remark, as a point of concern, how retrievals obtain much higher significances than originally reported. However, this stems from the injection of a fundamentally different signal. We demonstrate that their Hubble light curve exhibits ~20% higher noise and discards 11% of the useful data, which compromises its ability to recover the subtle signal of Kepler-1625 b-i.

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Fig. 1: Hubble light curves of Kepler-1625 b.
Fig. 2: Kepler light curves of Kepler-1708 b.

Data availability

The data that support the plots within this Matters Arising and other findings of this study are available via Dryad at https://doi.org/10.5061/dryad.zs7h44jh4 (ref. 13) or from the corresponding author upon reasonable request.

Code availability

The MultiNest7 regression algorithm is publicly available via GitHub at https://github.com/farhanferoz/MultiNest. The cofiam software package was released along with the original paper4 and is available via Dryad at https://doi.org/10.5061/dryad.18931zcz9 (ref. 14). The LUNA10 forward model is publicly available at https://sourceforge.net/p/lunamod. The SatCand package is publicly available via GitHub at https://github.com/Multiversario/satcand.

References

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Acknowledgements

D.K. thanks donors D. Daughaday, E. West, T. Zajonc, A. de Vaal, M. Elliott, S. Lee, Z. Danielson, C. Souter, M. Gillette, T. Jeffcoat, J. Rockett, T. Donkin, A. Schoen, R. Ramezankhani, S. Marks, N. Gebben, M. Hedlund, L. Deacon, R. Provost, N. De Haan, E. Garland, The Queen Road Foundation Inc., S. Thayer, I. Williams, X. Yao, A. Nimmerjahn, B. Cartmell, G. Le Saint, D. Ohman, R. Raszka, B. van Gaalen, A. Taylor and J. Alley. D.K. and D.A.Y. acknowledge support from NASA grant number 80NSSC21K0960. D.A.Y. thanks the LSSTC Data Science Fellowship Program, which is funded by LSSTC, NSF Cybertraining grant number 1829740, the Brinson Foundation and the Moore Foundation. J.S. acknowledges the financial support from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (grant agreement number 948467). Analysis was carried out in part on the NASA Supercomputer PLEIADES (grant number HEC-SMD-17-1386), provided by the NASA High-End Computing (HEC) Program through the NASA Advanced Supercomputing (NAS) Division at Ames Research Center. This paper includes data collected by the Kepler Mission. Funding for the Kepler Mission is provided by the NASA Science Mission directorate. This work is based in part on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. These observations are associated with program number GO-15149. Support for program number GO-15149 was provided by NASA through a grant from the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555.

Author information

Authors and Affiliations

  1. Department of Astronomy, Columbia University, New York, NY, USA

    David Kipping, Daniel A. Yahalomi & Ben Cassese

  2. Institute of Astronomy and Astrophysics, Academia Sinica, Taipei, Taiwan

    Alex Teachey

  3. Department of Applied Mathematics and Physics, Valdosta State University, Valdosta, GA, USA

    Billy Quarles

  4. NASA Ames Research Center, Moffett Field, CA, USA

    Steve Bryson

  5. Mani Bhaumik Institute for Theoretical Physics, Department of Physics and Astronomy, University of California, Los Angeles, Los Angeles, CA, USA

    Brad Hansen

  6. Institute for Particle Physics and Astrophysics, ETH Zurich, Zurich, Switzerland

    Judit Szulágyi

  7. Department of Physics and Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, Cambridge, MA, USA

    Chris Burke

  8. Caltech/IPAC-NASA Exoplanet Science Institute, Pasadena, CA, USA

    Kevin Hardegree-Ullman

Authors
  1. David Kipping
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  2. Alex Teachey
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  3. Daniel A. Yahalomi
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  4. Ben Cassese
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  8. Judit Szulágyi
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  9. Chris Burke
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  10. Kevin Hardegree-Ullman
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Contributions

D.K. performed the data reduction, analysis and interpretation and wrote the majority of the text. A.T. performed much of the original TK18 analysis and consulted on all relevant sections here. B.C. benchmarked the LUNA and Pandora codes. D.A.Y. used the wotan code to compare light curve products. B.Q. performed the tidal migration analysis and wrote the corresponding Supplementary Information section. B.H., S.B., J.S., C.B. and K.H.-U. helped to edit the final version of the manuscript.

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Correspondence to David Kipping.

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The authors declare no competing interests.

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

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Supplementary information

Supplementary Information

Supplementary Figs. 1–3, discussion and Tables 1 and 2.

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Kipping, D., Teachey, A., Yahalomi, D.A. et al. Concerning the possible exomoons around Kepler-1625 b and Kepler-1708 b. Nat Astron 9, 795–798 (2025). https://doi.org/10.1038/s41550-025-02547-1

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