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:

A new rotation period and longitude system for Uranus

Nature Astronomy volume 9, pages 658–665 (2025)Cite this article

Subjects

Abstract

The rotation period of Uranus was estimated to be 17.24 ± 0.01 h in 1986 from radio auroral measurements during the brief Voyager 2 flyby. This value is the basis for the Uranian SIII longitude system still in use. However, the poor period uncertainty limited its validity to a few years, after which the orientation of the magnetic axis was lost. Alternate, conflicting, rotation periods have also been proposed since then. Here we use the long-term tracking of Uranus’ magnetic poles between 2011 and 2022 from Hubble Space Telescope images of its ultraviolet aurorae to achieve an updated, independent, extremely precise rotation period of 17.247864 ± 0.000010 h, only consistent with the Voyager 2 estimate. Its 28-s-longer value and improved accuracy yields a new longitude model now valid over decades, up to the arrival of any future Uranus mission, which will allow the reanalysis of the whole set of Uranus observations. In addition, it has strong direct implications for formation scenarios, interior models, dynamo theories and studies of the magnetosphere. This approach stands as a new method to determine the rotation rate of any object hosting a magnetosphere and a rotationally modulated aurorae, in our Solar System and beyond.

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

Access options

Buy this article

  • Purchase on SpringerLink
  • Instant access to the full article PDF.

USD 39.95

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

Fig. 1: Selection of six HST/STIS far-UV images of the Uranian aurorae from 2011 to 2022.
Fig. 2: Determination of the Uranus rotation period.
Fig. 3: Extended set of HST images of the Uranian aurorae from 2005 to 2022.

Similar content being viewed by others

Data availability

This Article is based on observations acquired with the HST, operated by NASA and ESA, through the observing programmes GO nos. 7439, 10502, 12601, 13012, 14036, 16313 and 17214 and DDT no. 15380. The data are available via the STSci MAST archive at https://mast.stsci.edu and the processed data via the CNRS/INSU APIS observation service operated by PADC/LIRA at https://apis.obspm.fr. The CNRS/INSU Miriade ephemeris service, operated by Laboratoire Temps-Espace (LTE, known before 1 January 2025 as IMCCE for Institut de Mécanique Céleste et de Calcul des Ephémérides) at Observatoire de Paris, is available at https://ssp.imcce.fr/webservices/miriade/. The data can be queried through a web interface or URL queries. An example of a URL query using the updated rotation period to obtain IAUnew SIII longitudes is available at https://ssp.imcce.fr/webservices/miriade/api/ephemph.php?-name=p:Uranus&-type=planet&-ep=2000-01-01T12:00:00&-nbd=2&-step=1h&-observer=@500&-so=3&-mime=text&-output=--coord(eq2000).

References

  1. Archinal, B. A. et al. Report of the IAU Working Group on cartographic coordinates and rotational elements: 2015. Celest. Mech. Dyn. Astr. 130, 22 (2018).

    Article  ADS  MathSciNet  Google Scholar 

  2. Ness, N. F. et al. Magnetic fields at Uranus. Science 233, 85–87 (1986).

    Article  ADS  Google Scholar 

  3. Warwick, J. W. et al. Voyager 2 radio observations of Uranus. Science 233, 74–79 (1986).

    Article  Google Scholar 

  4. Broadfoot, A. L. et al. Ultraviolet spectrometer observations of Uranus. Science 233, 102–106 (1986).

    Article  Google Scholar 

  5. Lamy, L. Auroral emissions from Uranus and Neptune. Phil. Trans. R. Soc. A 378, 20190481 (2020).

    Article  ADS  Google Scholar 

  6. Desch, M. D., Connerney, J. E. P. & Kaiser, M. L. The rotation period of Uranus. Nature 322, 42–43 (1986).

    Article  ADS  Google Scholar 

  7. Connerney, J. E. P. & Acuna, M. H. The magnetic field of Uranus. J. Geophys. Res. 92, 15329–15336 (1987).

    Article  ADS  Google Scholar 

  8. Herbert, F. & Sandel, B. R. The Uranian aurora and its relationship to the magnetosphere. J. Geophys. Res. 99, 4143–4160 (1994).

    Article  ADS  Google Scholar 

  9. Herbert, F. Aurora and magnetic field of Uranus. J. Geophys. Res. 114, A11206 (2009).

    ADS  Google Scholar 

  10. Lamy, L. et al. Earth-based detection of Uranus’ aurorae. Geophys. Res. Lett. 39, L07105 (2012).

    Article  ADS  Google Scholar 

  11. Lamy, L. et al. The aurorae of Uranus past equinox. J. Geophys. Res. Space Phys. 122, 3997–4008 (2017).

    Article  ADS  Google Scholar 

  12. Lamy, L. et al. Analysis of HST, VLT and Gemini coordinated observations of Uranus late 2017: a multi-spectral search for auroral signatures. In SF2A-2018: Proc. Annual Meeting of the French Society of Astronomy and Astrophysics (eds Di Matteo, P. et al) 29–32 (SF2A, 2018).

  13. Berthier, J., Descamps, P. & Mignard, F. Introduction aux éphémérides et phénomènes astronomiques ISBN 978-2-7598-2414-4 (IMCCE and EDP Sciences, 2021).

  14. Moore, K. M. et al. Time variation of Jupiter’s internal magnetic field consistent with zonal wind advection. Nat. Astron. 3, 730–735 (2019).

    Article  ADS  Google Scholar 

  15. Higgins, C. A. et al. A redefinition of Jupiter’s rotation period. J. Geophys. Res. 102, 22033–22041 (1997).

    Article  ADS  Google Scholar 

  16. Helled, R., Anderson, J. D. & Schubert, G. Uranus and Neptune: shape and rotation. Icarus 210, 446–454 (2010).

    Article  ADS  Google Scholar 

  17. Nettelmann, N., Helled, R., Fortney, J. J. & Redemer, R. New indication for a dichotomy in the interior structure of Uranus and Neptune from the application of modified shape and rotation data. Planet. Space Sci. 77, 143–151 (2013).

    Article  ADS  Google Scholar 

  18. Helled, R., Nettelmann, N. & Guillot, T. Uranus and Neptune: origin, evolution and internal structure. Space Sci. Rew. 216, 38 (2020).

    Article  ADS  Google Scholar 

  19. Brown, L. W. Possible radio emission from Uranus at 0.5 MHz. Astrophys. J. 207, 209–212 (1976).

    Article  Google Scholar 

  20. Dunn, W. R. et al. A low signal detection of X-rays from Uranus. J. Geophys. Res. Space Phys. 126, e2020JA028739 (2021).

    Article  ADS  Google Scholar 

  21. Clarke, J. D. et al. Continued observations of the H Ly a emission from Uranus. J. Geophys. Res. 91, 8771–8781 (1986).

    Article  ADS  Google Scholar 

  22. Joshi, S. et al. Uranus' hydrogen upper atmosphere: insights from pre- and post-equinox HST Lyman-α images. Astron. Astrophys. 693, A231 (2025).

    Article  Google Scholar 

  23. Lam, H. A. et al. Variation in the H3+ emission of Uranus. Astrophs. J. 474, 73–76 (1997).

    Article  Google Scholar 

  24. Melin, H. et al. The H3+ ionosphere of Uranus: decades-long cooling and local-time morphology. Phil. Trans. R. Soc. A 377, 20180408 (2019).

    Article  ADS  Google Scholar 

  25. Thomas, E. M. et al. Detection of the infrared aurora at Uranus with Keck-NIRSPEC. Nat. Astron. 7, 1473–1480 (2023).

    Article  ADS  Google Scholar 

  26. Louis, C. K. et al. Predictions for Uranus-moons radio emissions and comparison with Voyager 2/PRA observations. Planet. Radio Em. https://doi.org/10.25546/103106 (2022).

  27. Toth, G. et al. Three-dimensional MHD simulations of the magnetosphere of Uranus. J. Geophys. Res. 109, A11210 (2004).

    ADS  Google Scholar 

  28. Masters, A. Magnetic reconnection at Uranus’ magnetopause. J. Geophys. Res. Space Phys. 115, 5520–5538 (2014).

    Article  ADS  Google Scholar 

  29. Cao, X. & Paty, C. Diurnal and seasonal variability of Uranus’ magnetosphere. J. Geophys. Res. Space Phys. 122, 6318–6331 (2017).

    Article  ADS  Google Scholar 

  30. Griton, L., Pantellini, F. & Meliani, Z. Three-dimensional MHD simulations of the solar wind interaction with a hyperfact-rotating Uranus. J. Geophys. Res. Space Phys. 123, 2018JA025331 (2018).

    Article  Google Scholar 

  31. Pantellini, F. A physical model for the magnetosphere of Uranus at solstice time. Astron. Astrophys. 643, A144 (2020).

    Article  ADS  Google Scholar 

  32. Arridge, C. S. et al. The science case for an orbital mission to Uranus: exploring the origins and evolution of ice giant planets. Planet. Space Sci. 104, 122–140 (2023).

    Article  ADS  Google Scholar 

  33. Origins, Worlds, and Life, A Decadal Strategy for Planetary Science and Astrobiology 2023–2032 (NASA, 2023).

  34. Vincent, M. B. et al. Mapping Jupiter’s latitudinal bands and great red spot using HST/WFPC2 far-ultraviolet imaging. Icarus 143, 189–204 (2000).

    Article  ADS  Google Scholar 

  35. Gustin, J., Bonfond, B., Grodent, D. & Gérard, J.-C. Conversion from HST ACS and STIS auroral counts into brightness, precipitated power, and radiated power for H2 giant planets. J. Geophys. Res. 117, A07316 (2012).

    ADS  Google Scholar 

  36. Lamy, L., Prangé, R., Henry, F. & Le Sidaner, P. The Auroral Planetary Imaging and Spectroscopy (APIS) service. Astron. Comput. 11, 138–145 (2015).

    Article  ADS  Google Scholar 

  37. Barthélémy, M. et al. Dayglow and auroral emissions of Uranus in H2 FUV bands. Icarus 239, 160–167 (2014).

    Article  ADS  Google Scholar 

  38. Schultz, M. & McNab, M. C. Source-surface modeling of planetary magnetospheres. J. Geophys. Res. 101, 5095–5118 (1996).

    Article  ADS  Google Scholar 

Download references

Acknowledgements

We thank C. Leitherer for HST director’s time allocated in 2020 and Alison Sherwin as our programme coordinator. The French authors thank the CNES spatial agency and CNRS/INSU national programmes of heliophysics (PNST, also funded by CEA) and planetology (PNP). C.T. was supported by JSPS KAKENHI (grant no. 20KK0074). W.R.D. was supported by Ernest Rutherford Fellowship ST/W003449/1. L.R. appreciates support from the Swedish National Space Agency through grant nos. 2020-00187 and 2021-00153.

Author information

Authors and Affiliations

  1. LIRA, Observatoire de Paris, Université PSL, Sorbonne Université, Université Paris Cité, Cergy Paris Université, CNRS, Meudon, France

    L. Lamy & R. Prangé

  2. LAM, Aix Marseille Université, CNRS, CNES, Marseille, France

    L. Lamy

  3. LTE, Observatoire de Paris, Université PSL, Sorbonne Université, Université de Lille, LNE, CNRS, Paris, France

    J. Berthier

  4. National Institute of Information and Communications Technology, Tokyo, Japan

    C. Tao

  5. Center for Space Plasma and Aeronomic Research, University of Alabama, Huntsville, AL, USA

    T. Kim

  6. Space and Plasma Physics, KTH Royal Institute of Technology, Stockholm, Sweden

    L. Roth

  7. IPAG, Université Grenoble Alpes, CNRS, Grenoble, France

    M. Barthélémy

  8. LATMOS-IPSL, CNRS, UVSQ, Paris-Saclay, Sorbonne Université, Guyancourt, France

    J.-Y. Chaufray

  9. Applied Physics Laboratory, John Hopkins University, Laurel, MD, USA

    A. Rymer

  10. Mullard Space Science Laboratory, University College London, Dorking, UK

    W. R. Dunn

  11. The Centre for Planetary Science at UCL/Birkbeck, London, UK

    W. R. Dunn

  12. Astronomy and Astrophysics Section, School of Cosmic Physics, Dublin Institute for Advanced Studies, DIAS Dunsink Observatory, Dublin, Ireland

    A. D. Wibisono

  13. Department of Mathematics, Physics, and Electrical Engineering, Northumbria University, Newcastle upon Tyne, UK

    H. Melin

Authors
  1. L. Lamy
    View author publications

    Search author on:PubMed Google Scholar

  2. R. Prangé
    View author publications

    Search author on:PubMed Google Scholar

  3. J. Berthier
    View author publications

    Search author on:PubMed Google Scholar

  4. C. Tao
    View author publications

    Search author on:PubMed Google Scholar

  5. T. Kim
    View author publications

    Search author on:PubMed Google Scholar

  6. L. Roth
    View author publications

    Search author on:PubMed Google Scholar

  7. M. Barthélémy
    View author publications

    Search author on:PubMed Google Scholar

  8. J.-Y. Chaufray
    View author publications

    Search author on:PubMed Google Scholar

  9. A. Rymer
    View author publications

    Search author on:PubMed Google Scholar

  10. W. R. Dunn
    View author publications

    Search author on:PubMed Google Scholar

  11. A. D. Wibisono
    View author publications

    Search author on:PubMed Google Scholar

  12. H. Melin
    View author publications

    Search author on:PubMed Google Scholar

Contributions

L.L. led and processed the HST observations, conducted their analysis and wrote the paper. R.P. contributed to the data analysis, to the physical interpretation and to the writing of the paper. J.B. helped with the analytical determination of planetocentric ephemeris and developed a module on the LTE/Miriade online service that enables the user to choose the planetary parameters. C.T. and T.K. performed MHD simulations of the solar wind that were used to schedule the observations and counter-checked the derived longitudes. All the authors read and commented the paper.

Corresponding author

Correspondence to L. Lamy.

Ethics declarations

Competing interests

The authors declare no competing interests.

Peer review

Peer review information

Nature Astronomy thanks Richard Holme and Xianzhe Jia for their contribution to the peer review of this work.

Additional information

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

Supplementary information

Supplementary Information

Supplementary Figs. 1–5 and Video 1.

Supplementary Video 1

Position of the prime meridian (left) and planetary configuration with the prime meridian (right) in red as a function of time over 1985–2069 (one frame per month) for a terrestrial observer and a non-rotating Uranus (W1 = 0). This animation illustrates the effect of the proper motion of Uranus along its orbit onto the position of the prime meridian used to compute IAU longitudes.

Rights and permissions

Springer Nature or its licensor (e.g. a society or other partner) holds exclusive rights to this article under a publishing agreement with the author(s) or other rightsholder(s); author self-archiving of the accepted manuscript version of this article is solely governed by the terms of such publishing agreement and applicable law.

Reprints and permissions

About this article

Check for updates. Verify currency and authenticity via CrossMark

Cite this article

Lamy, L., Prangé, R., Berthier, J. et al. A new rotation period and longitude system for Uranus. Nat Astron 9, 658–665 (2025). https://doi.org/10.1038/s41550-025-02492-z

Download citation

  • Received:

  • Accepted:

  • Published:

  • Version of record:

  • Issue date:

  • DOI: https://doi.org/10.1038/s41550-025-02492-z

This article is cited by

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