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:

Bow shock and Local Bubble plasma unveiled by the scintillating millisecond pulsar J0437−4715

Nature Astronomy volume 9, pages 1053–1063 (2025)Cite this article

Subjects

Abstract

The ionized interstellar medium contains astronomical-unit-scale (and below) structures that scatter radio waves from pulsars, resulting in scintillation. Power spectral analysis of scintillation often shows parabolic arcs, with curvatures that encode the locations and kinematics of the pulsar, Earth and interstellar plasma. Here we report the discovery of 25 distinct plasma structures in the direction of the brilliant millisecond pulsar, PSR J0437−4715, in observations obtained with the MeerKAT radio telescope. Four arcs reveal structures within 5,000 au of the pulsar, from a series of shocks induced as the pulsar and its wind interact with the ambient interstellar medium. The measured radial distance and velocity of the main shock allow us to solve the shock geometry and space velocity of the pulsar in three dimensions, whereas the velocity of another structure unexpectedly indicates a back flow from the direction of the shock or pulsar-wind tail. The remaining 21 arcs represent a surprising abundance of structures sustained by turbulence within the Local Bubble, which is a region of the interstellar medium thought to be depleted of gas by a series of supernova explosions about 14 Myr ago. The Local Bubble is cool enough in areas for subastronomical-unit density fluctuations to arise from turbulence.

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: Dynamic spectrum of intensity from a MeerKAT observation of PSR J0437−4715 on MJD 58843.
Fig. 2: Secondary spectrum from a MeerKAT observation of PSR J0437−4715 on MJD 58843.
Fig. 3: Measurements and models for all of the scintillation arcs described in this work.
Fig. 4: Schematic of the PSR J0437−4715 bow-shock system, depicting the main boundaries that we propose are associated with the scintillation arcs in the MeerKAT observations.
Fig. 5: Hα image of the bow shock of PSR J0437−4715 with our hyperboloid model of the shocked ISM behind the forward shock.

Similar content being viewed by others

Data availability

The dynamic spectra from our observations are available via figshare at https://doi.org/10.6084/m9.figshare.27311715 (ref. 65). Any further data may be provided upon reasonable request to the corresponding author.

Code availability

Code for processing the dynamic spectra and the interactive tools for arc identification and curvature fitting are available at http://github.com/danielreardon/J0437-Scintillation-arcs, including the parameters used to model screens for this work.

References

  1. Armstrong, J. W., Rickett, B. J. & Spangler, S. R. Electron density power spectrum in the local interstellar medium. Astrophys. J. 443, 209 (1995).

    Article  ADS  Google Scholar 

  2. Goldreich, P. & Sridhar, S. Toward a theory of interstellar turbulence. II. Strong Alfvenic turbulence. Astrophys. J. 438, 763 (1995).

    ADS  Google Scholar 

  3. Rickett, B. J. Frequency structure of pulsar intensity variations. Nature 221, 158–159 (1969).

    Article  ADS  Google Scholar 

  4. Cordes, J. M., Pidwerbetsky, A. & Lovelace, R. V. E. Refractive and diffractive scattering in the interstellar medium. Astrophys. J. 310, 737 (1986).

    Article  ADS  Google Scholar 

  5. Rickett, B. J. Radio propagation through the turbulent interstellar plasma. Annu. Rev. Astron. Astrophys. 28, 561–605 (1990).

    Article  ADS  Google Scholar 

  6. Bailes, M. et al. The MeerKAT telescope as a pulsar facility: system verification and early science results from MeerTime. Publ. Astron. Soc. Aust. 37, e028 (2020).

    Article  ADS  Google Scholar 

  7. Stinebring, D. R. et al. Faint scattering around pulsars: probing the interstellar medium on Solar System size scales. Astrophys. J. Lett. 549, L97–L100 (2001).

    Article  ADS  Google Scholar 

  8. Walker, M. A., Melrose, D. B., Stinebring, D. R. & Zhang, C. M. Interpretation of parabolic arcs in pulsar secondary spectra. Mon. Not. R. Astron. Soc. 354, 43–54 (2004).

    Article  ADS  Google Scholar 

  9. Cordes, J. M., Rickett, B. J., Stinebring, D. R. & Coles, W. A. Theory of parabolic arcs in interstellar scintillation spectra. Astrophys. J. 637, 346–365 (2006).

    Article  ADS  Google Scholar 

  10. Yao, J. et al. Evidence for three-dimensional spin-velocity alignment in a pulsar. Nat. Astron. 5, 788–795 (2021).

    Article  ADS  Google Scholar 

  11. Serafin Nadeau, T. et al. A cacophony of echoes from daily monitoring of the Crab Pulsar at Jodrell Bank. Astrophys. J. 962, 57 (2024).

    Article  ADS  Google Scholar 

  12. Lin, F. X. et al. Plasma lensing near the eclipses of the Black Widow pulsar B1957+20. Mon. Not. R. Astron. Soc. 519, 121–135 (2023).

    Article  ADS  Google Scholar 

  13. Bell, J. F., Bailes, M. & Bessell, M. S. Optical detection of the companion of the millisecond pulsar J0437−4715. Nature 364, 603–605 (1993).

    Article  ADS  Google Scholar 

  14. Reardon, D. J. et al. Precision orbital dynamics from interstellar scintillation arcs for PSR J0437−4715. Astrophys. J. 904, 104 (2020).

    Article  ADS  Google Scholar 

  15. Johnston, S. et al. Discovery of a very bright, nearby binary millisecond pulsar. Nature 361, 613–615 (1993).

    Article  ADS  Google Scholar 

  16. van Straten, W. et al. A test of general relativity from the three-dimensional orbital geometry of a binary pulsar. Nature 412, 158–160 (2001).

    Article  ADS  Google Scholar 

  17. Reardon, D. J. et al. The neutron star mass, distance, and inclination from precision timing of the brilliant millisecond pulsar J0437−4715. Astrophys. J. Lett. 971, L18 (2024).

    Article  Google Scholar 

  18. Brownsberger, S. & Romani, R. W. A survey for Hα pulsar bow shocks. Astrophys. J. 784, 154 (2014).

    Article  ADS  Google Scholar 

  19. Rangelov, B. et al. First detection of a pulsar bow shock nebula in far-UV: PSR J0437−4715. Astrophys. J. 831, 129 (2016).

    Article  ADS  Google Scholar 

  20. Wilkin, F. P. Exact analytic solutions for stellar wind bow shocks. Astrophys. J. Lett. 459, L31 (1996).

    Article  ADS  Google Scholar 

  21. Bucciantini, N. Pulsar bow-shock nebulae. II. Hydrodynamical simulation. Astron. Astrophys. 387, 1066–1073 (2002).

    Article  ADS  Google Scholar 

  22. Vigelius, M., Melatos, A., Chatterjee, S., Gaensler, B. M. & Ghavamian, P. Three-dimensional hydrodynamic simulations of asymmetric pulsar wind bow shocks. Mon. Not. R. Astron. Soc. 374, 793–808 (2007).

    Article  ADS  Google Scholar 

  23. Romani, R. W. et al. The bow shock and kinematics of PSR J1959+2048. Astrophys. J. 930, 101 (2022).

    Article  ADS  Google Scholar 

  24. Ocker, S. K. et al. Pulsar scintillation through thick and thin: bow shocks, bubbles, and the broader interstellar medium. Mon. Not. R. Astron. Soc. 527, 7568–7587 (2024).

    Article  ADS  Google Scholar 

  25. Wilkin, F. P. Modeling nonaxisymmetric bow shocks: solution method and exact analytic solutions. Astrophys. J. 532, 400–414 (2000).

    Article  ADS  Google Scholar 

  26. Shklovskii, I. S. Possible causes of the secular increase in pulsar periods. Sov. Astron. 13, 562 (1970).

    ADS  Google Scholar 

  27. van Straten, W. High-precision Timing and Polarimetry of PSR J0437−4715. Ph.D. thesis, Swinburne Univ. of Technology, Australia (2003).

  28. Liu, X. J., Bassa, C. G. & Stappers, B. W. High-precision pulsar timing and spin frequency second derivatives. Mon. Not. R. Astron. Soc. 478, 2359–2367 (2018).

    Article  ADS  Google Scholar 

  29. Agazie, G. et al. The NANOGrav 15 yr data set: evidence for a gravitational-wave background. Astrophys. J. Lett. 951, L8 (2023).

    Article  ADS  Google Scholar 

  30. Reardon, D. J. et al. Search for an isotropic gravitational-wave background with the Parkes Pulsar Timing Array. Astrophys. J. Lett. 951, L6 (2023).

    Article  ADS  Google Scholar 

  31. EPTA Collaboration and InPTA collaboration et al. The second data release from the European Pulsar Timing Array III. Search for gravitational wave signals. Astron. Astrophys. 678, A50 (2023).

    Article  Google Scholar 

  32. Xu, H. et al. Searching for the nano-Hertz stochastic gravitational wave background with the Chinese pulsar timing array data release I. Res. Astron. Astrophys. 23, 075024 (2023).

    Article  ADS  Google Scholar 

  33. Pen, U.-L. & Levin, Y. Pulsar scintillations from corrugated reconnection sheets in the interstellar medium. Mon. Not. R. Astron. Soc. 442, 3338–3346 (2014).

    Article  ADS  Google Scholar 

  34. Deller, A. T., Verbiest, J. P. W., Tingay, S. J. & Bailes, M. Extremely high precision VLBI astrometry of PSR J0437−4715 and implications for theories of gravity. Astrophys. J. Lett. 685, L67 (2008).

    Article  ADS  Google Scholar 

  35. Yeh, K. C. & Liu, C. H. Radio wave scintillations in the ionosphere. Proc. IEEE 70, 324–360 (1982).

    Article  ADS  Google Scholar 

  36. McKee, J. W., Zhu, H., Stinebring, D. R. & Cordes, J. M. Probing the local interstellar medium with scintillometry of the bright pulsar B1133+16. Astrophys. J. 927, 99 (2022).

    Article  ADS  Google Scholar 

  37. Pelgrims, V., Ferrière, K., Boulanger, F., Lallement, R. & Montier, L. Modeling the magnetized Local Bubble from dust data. Astron. Astrophys. 636, A17 (2020).

    Article  ADS  Google Scholar 

  38. Zucker, C. et al. Star formation near the Sun is driven by expansion of the Local Bubble. Nature 601, 334–337 (2022).

    Article  ADS  Google Scholar 

  39. Lallement, R. et al. Gaia-2MASS 3D maps of Galactic interstellar dust within 3 kpc. Astron. Astrophys. 625, A135 (2019).

    Article  Google Scholar 

  40. Spangler, S. R. Plasma turbulence in the Local Bubble. Space Sci. Rev. 143, 277–290 (2009).

    Article  ADS  Google Scholar 

  41. Linsky, J. L. & Redfield, S. Could the Local Cavity be an irregularly shaped Strömgren sphere? Astrophys. J. 920, 75 (2021).

    Article  ADS  Google Scholar 

  42. Kim, C.-G., Ostriker, E. C. & Raileanu, R. Superbubbles in the multiphase ISM and the loading of Galactic winds. Astrophys. J. 834, 25 (2017).

    Article  ADS  Google Scholar 

  43. Welsh, B. Y., Lallement, R., Vergely, J. L. & Raimond, S. New 3D gas density maps of NaI and CaII interstellar absorption within 300 pc. Astron. Astrophys. 510, A54 (2010).

    Article  Google Scholar 

  44. van Straten, W., Demorest, P. & Oslowski, S. Pulsar data analysis with PSRCHIVE. Astron. Res. Technol. 9, 237–256 (2012).

    Google Scholar 

  45. Lazarus, P. et al. Prospects for high-precision pulsar timing with the new Effelsberg PSRIX backend. Mon. Not. R. Astron. Soc. 458, 868–880 (2016).

    Article  ADS  Google Scholar 

  46. Reardon, D. J. Scintools: pulsar scintillation data tools. Astrophysics Source Code Library ascl:2011.019 (2020).

  47. Damelin, S. B. & Hoang, N. S. On surface completion and image inpainting by biharmonic functions: numerical aspects. Preprint at https://arxiv.org/abs/1707.06567 (2017).

  48. Lin, F. X., Main, R. A., Verbiest, J. P. W., Kramer, M. & Shaifullah, G. Discovery and modelling of broad-scale plasma lensing in black-widow pulsar J2051 - 0827. Mon. Not. R. Astron. Soc. 506, 2824–2835 (2021).

    Article  ADS  Google Scholar 

  49. Sprenger, T., Wucknitz, O., Main, R., Baker, D. & Brisken, W. The θ–θ diagram: transforming pulsar scintillation spectra to coordinates on highly anisotropic interstellar scattering screens. Mon. Not. R. Astron. Soc. 500, 1114–1124 (2021).

    Article  ADS  Google Scholar 

  50. Stinebring, D. R. et al. A scintillation arc survey of 22 pulsars with low to moderate dispersion measures. Astrophys. J. 941, 34 (2022).

    Article  ADS  Google Scholar 

  51. Main, R. A. et al. The Thousand Pulsar Array programme on MeerKAT - X. Scintillation arcs of 107 pulsars. Mon. Not. R. Astron. Soc. 518, 1086–1097 (2023).

    Article  ADS  Google Scholar 

  52. Savitzky, A. & Golay, M. J. E. Smoothing and differentiation of data by simplified least squares procedures. Anal. Chem. 36, 1627–1639 (1964).

    Article  ADS  Google Scholar 

  53. Astropy Collaboration et al. 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 

  54. Reardon, D. J. et al. Timing analysis for 20 millisecond pulsars in the Parkes Pulsar Timing Array. Mon. Not. R. Astron. Soc. 455, 1751–1769 (2016).

    Article  ADS  Google Scholar 

  55. Thrane, E. & Talbot, C. An introduction to Bayesian inference in gravitational-wave astronomy: parameter estimation, model selection, and hierarchical models. Publ. Astron. Soc. Aust. 36, e010 (2019).

    Article  ADS  Google Scholar 

  56. Ashton, G. et al. BILBY: a user-friendly Bayesian inference library for gravitational-wave astronomy. Astrophys. J. Suppl. Ser. 241, 27 (2019).

    Article  ADS  Google Scholar 

  57. Speagle, J. S. DYNESTY: a dynamic nested sampling package for estimating Bayesian posteriors and evidences. Mon. Not. R. Astron. Soc. 493, 3132–3158 (2020).

    Article  ADS  Google Scholar 

  58. Walker, K., Reardon, D. J., Thrane, E. & Smith, R. Orbital dynamics and extreme scattering event properties from long-term scintillation observations of PSR J1603−7202. Astrophys. J. 933, 16 (2022).

    Article  ADS  Google Scholar 

  59. Askew, J., Reardon, D. J. & Shannon, R. M. Analysis of the ionized interstellar medium and orbital dynamics of PSR J1909−3744 using scintillation arcs. Mon. Not. R. Astron. Soc. 519, 5086–5098 (2023).

    Article  ADS  Google Scholar 

  60. Kopeikin, S. M. On possible implications of orbital parallaxes of wide orbit binary pulsars and their measurability. Astrophys. J. Lett. 439, L5 (1995).

    Article  ADS  Google Scholar 

  61. The Bow Shock of the Nearest Millisecond Pulsar. STScI https://www.stsci.edu/~fruchter/nebula/ (1995).

  62. O’Rourke, J. Computational Geometry in C 2nd edn (Cambridge Univ. Press, 1998).

  63. Lee, L. C. & Jokipii, J. R. Strong scintillations in astrophysics. II. A theory temporal broadening pulses Astrophys. J. 201, 532–543 (1975).

    ADS  Google Scholar 

  64. Reardon, D. J. & Coles, W. A. Determining electron column density fluctuations in a dominant scattering region using pulsar scintillation. Mon. Not. R. Astron. Soc. 521, 6392–6400 (2023).

    Article  ADS  Google Scholar 

  65. Reardon, D. J. et al. Dynamic spectra from observations described in "Bow Shock and Local Bubble Plasma Unveiled by the Scintillating Millisecond Pulsar J0437-4715". figshare https://doi.org/10.6084/m9.figshare.27311715 (2025).

Download references

Acknowledgements

The MeerKAT telescope is operated by the South African Radio Astronomy Observatory, which is a facility of the National Research Foundation, an agency of the Department of Science and Innovation. Part of this work was undertaken as part of the Australian Research Council Centre of Excellence for Gravitational Wave Discovery (project nos CE170100004 and CE230100016). R.M.S. acknowledges support through Australian Research Council Future Fellowship FT190100155. A.P. acknowledges financial support from the European Research Council (ERC) starting grant ‘GIGA’ (grant agreement no. 101116134) and through the NWO-I Veni fellowship.

Author information

Authors and Affiliations

  1. Centre for Astrophysics and Supercomputing, Swinburne University of Technology, Hawthorn, Victoria, Australia

    Daniel J. Reardon, Ryan M. Shannon, Matthew Bailes, Andrew Jameson & Renée Spiewak

  2. Australian Research Council Centre of Excellence for Gravitational Wave Discovery (OzGrav), Hawthorn, Victoria, Australia

    Daniel J. Reardon, Ryan M. Shannon & Matthew Bailes

  3. Max-Planck-Institut für Radioastronomie, Bonn, Germany

    Robert Main, Michael Kramer, Aditya Parthasarathy & Vivek Venkatraman Krishnan

  4. Department of Physics, McGill University, Montréal, Quebec, Canada

    Robert Main

  5. Trottier Space Institute, McGill University, Montréal, Quebec, Canada

    Robert Main

  6. Cahill Center for Astronomy and Astrophysics, California Institute of Technology, Pasadena, CA, USA

    Stella Koch Ocker

  7. The Observatories of the Carnegie Institution for Science, Pasadena, CA, USA

    Stella Koch Ocker

  8. South African Radio Astronomy Observatory, Liesbeek House, Cape Town, South Africa

    Fernando Camilo & Marisa Geyer

  9. High Energy Physics, Cosmology & Astrophysics Theory (HEPCAT) Group, Department of Mathematics & Applied Mathematics, University of Cape Town, Cape Town, South Africa

    Marisa Geyer

  10. ASTRON, Netherlands Institute for Radio Astronomy, Dwingeloo, the Netherlands

    Aditya Parthasarathy

  11. Anton Pannekoek Institute for Astronomy, University of Amsterdam, Amsterdam, the Netherlands

    Aditya Parthasarathy

  12. Manly Astrophysics, Manly, New South Wales, Australia

    Willem van Straten

Authors
  1. Daniel J. Reardon
    View author publications

    Search author on:PubMed Google Scholar

  2. Robert Main
    View author publications

    Search author on:PubMed Google Scholar

  3. Stella Koch Ocker
    View author publications

    Search author on:PubMed Google Scholar

  4. Ryan M. Shannon
    View author publications

    Search author on:PubMed Google Scholar

  5. Matthew Bailes
    View author publications

    Search author on:PubMed Google Scholar

  6. Fernando Camilo
    View author publications

    Search author on:PubMed Google Scholar

  7. Marisa Geyer
    View author publications

    Search author on:PubMed Google Scholar

  8. Andrew Jameson
    View author publications

    Search author on:PubMed Google Scholar

  9. Michael Kramer
    View author publications

    Search author on:PubMed Google Scholar

  10. Aditya Parthasarathy
    View author publications

    Search author on:PubMed Google Scholar

  11. Renée Spiewak
    View author publications

    Search author on:PubMed Google Scholar

  12. Willem van Straten
    View author publications

    Search author on:PubMed Google Scholar

  13. Vivek Venkatraman Krishnan
    View author publications

    Search author on:PubMed Google Scholar

Contributions

D.J.R. devised the project, led the data analysis and drafted the manuscript. R.M. contributed to the analysis of the scintillation arcs and bow shock and assisted with manuscript preparation. S.K.O. contributed to the interpretation of the scintillation arcs and assisted with manuscript preparation. R.M.S. and M.B. were involved in observation planning and provided input on the manuscript. D.J.R., R.M.S., M.B., F.C., M.G., A.J., M.K., A.P., R.S., W.v.S. and V.V.K. contributed to the foundational work of the MeerTime project, which facilitated the collection of this dataset under the MeerKAT Pulsar Timing Array (MPTA) programme. All authors reviewed and provided feedback on the manuscript.

Corresponding author

Correspondence to Daniel J. Reardon.

Ethics declarations

Competing interests

The authors declare no competing interests.

Peer review

Peer review information

Nature Astronomy thanks Marten van Kerkwijk and Daniel Stinebring 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.

Extended data

Extended Data Fig. 1 Probability density contours for the pulsar distance, Dpsr and longitude of ascending node, Ω, derived from a high signal-to-noise scintillation arc.

Blue contours show the 68%, 95%, and 99.7% credible intervals for the posterior distribution inferred from the arc (‘ID 2’ in Table 1). The orange shaded regions show the precise 1σ (68%) confident intervals from pulsar timing (Reardon et al. 2024). The central 68% credible intervals inferred from the scintillation arc are \(\Omega =20{4}_{-13}^{+10}\) (degrees, East of North) and \({D}_{{\rm{psr}}}=15{8}_{-6}^{+3}\) pc.

Extended Data Fig. 2 Strength of scattering for each screen.

The maximum observed scattering angle (\({\alpha }_{\max }\)) is shown in blue for each screen with fractional screen distance (s). The solid and dashed horizontal lines show the mean and standard deviation of the \({\alpha }_{\max }\) values from screens attributed to interstellar plasma, \({\alpha }_{\max ,{\rm{ISM}}}=4.8\pm 0.8\) mas. The four bow shock scintillation arcs originate from notably larger scattering angles.

Extended Data Fig. 3 Location of the measured scattering screens along the line of sight to PSR J0437 − 4715, projected onto the Galactic plane.

The colour scale shows the Lallement et al. (2019) map of logarithmic differential extinction due to dust, \({\log }_{10}({A}_{v})\), where Av is in units of magnitude per parsec (M pc−1). The darker regions are used to define the latest (three-dimensional) Local Bubble model (Pelgrims et al. 2020).

Supplementary information

Supplementary Information

Supplementary Figs. 1 and 2.

Supplementary Video 1

Animated version of Fig. 2 in the main text, showing the scintillation arc curvatures changing with the orbital phase of the pulsar. Each frame of the animation shows the secondary spectrum from a ~12-h observation on an individual day, for six consecutive days of the observing campaign.

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

Reardon, D.J., Main, R., Ocker, S.K. et al. Bow shock and Local Bubble plasma unveiled by the scintillating millisecond pulsar J0437−4715. Nat Astron 9, 1053–1063 (2025). https://doi.org/10.1038/s41550-025-02534-6

Download citation

  • Received:

  • Accepted:

  • Published:

  • Version of record:

  • Issue date:

  • DOI: https://doi.org/10.1038/s41550-025-02534-6

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