Skip to main content

Thank you for visiting 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.

A Hubble constant measurement from superluminal motion of the jet in GW170817


The Hubble constant (H0) measures the current expansion rate of the Universe, and plays a fundamental role in cosmology. Tremendous effort has been dedicated over the past decades to measure H0 (refs. 1,2,3,4,5,6,7,8,9,10). Gravitational wave (GW) sources accompanied by electromagnetic (EM) counterparts offer an independent standard siren measurement of H0 (refs. 11,12,13), as demonstrated following the discovery of the neutron star merger, GW170817 (refs. 14,15,16). This measurement does not assume a cosmological model and is independent of a cosmic distance ladder. The first joint analysis of the GW signal from GW170817 and its EM localization led to a measurement of \(H_0 = 74_{ - 8}^{ + 16}\,{\mathrm{km}}\,{\mathrm{s}}^{-1}\,{\mathrm{Mpc}}^{-1}\) (median and symmetric 68% credible interval)13. In this analysis, the degeneracy in the GW signal between the source distance and the observing angle dominated the H0 measurement uncertainty. Recently, tight constraints on the observing angle using high angular resolution imaging of the radio counterpart of GW170817 have been obtained17. Here, we report an improved measurement \(H_0 = 70.3_{ - 5.0}^{ + 5.3}\,{\mathrm{km}}\,{\mathrm{s}}^{-1}\,{\mathrm{Mpc}}^{-1}\) by using these new radio observations, combined with the previous GW and EM data. We estimate that 15 more GW170817-like events, having radio images and light curve data, as compared with 50–100 GW events without such data18,19, will potentially resolve the tension between the Planck and Cepheid–supernova measurements.

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

Relevant articles

Open Access articles citing this article.

Access options

Rent or buy this article

Prices vary by article type



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

Fig. 1: Distance and observing angle constraints to GW170817.
Fig. 2: Posterior distributions for H0.
Fig. 3: The Hubble constant with different jet models.

Data availability

MCMC samples are available from the corresponding author on request.

Code availability

The codes used for generating the synthetic light curves are currently being readied for public release. Markov chain Monte Carlo Ensemble sampler: emcee.


  1. Hinshaw, G. et al. Nine-year Wilkinson Microwave Anisotropy Probe (WMAP) observations: cosmological parameter results. Astrophys. J. Suppl. Ser. 208, 19 (2013).

    Article  ADS  Google Scholar 

  2. Aubourg, É. et al. Cosmological implications of baryon acoustic oscillation measurements. Phys. Rev. D 92, 123516 (2015).

    Article  ADS  Google Scholar 

  3. Planck Collaboration, Planck 2015 results. XIII. Cosmological parameters. Astron. Astrophys. 594, A13 (2016).

  4. Riess, A. G. et al. A 2.4% determination of the local value of the Hubble constant. Astrophys. J. 826, 56 (2016).

    Article  ADS  Google Scholar 

  5. Beaton, R. L. et al. The Carnegie–Chicago Hubble Program. I. An independent approach to the extragalactic distance scale using only population II distance indicators. Astrophys. J. 832, 210 (2016).

    Article  ADS  Google Scholar 

  6. Gao, F. et al. The Megamaser Cosmology Project. VIII. A geometric distance to NGC 5765b. Astrophys. J. 817, 128 (2016).

    Article  ADS  Google Scholar 

  7. Jang, I. S. & Lee, M. G. The Tip of the Red Giant Branch distances to Type Ia supernova host galaxies. V. NGC 3021, NGC 3370, and NGC 1309 and the value of the Hubble constant. Preprint at (2017).

  8. Bonvin, V. et al. H0LiCOW – V. New COSMOGRAIL time delays of HE 0435–1223: H 0 to 3.8 per cent precision from strong lensing in a flat ΛCDM model. Mon. Not. R. Astron. Soc. 465, 4914–4930 (2017).

    Article  ADS  Google Scholar 

  9. Addison, G. E. et al. Elucidating ΛCDM: impact of baryon acoustic oscillation measurements on the Hubble constant discrepancy. Astrophys. J. 853, 119 (2018).

    Article  ADS  Google Scholar 

  10. DES Collaboration, Dark Energy Survey year 1 results: a precise H0 estimate from DES Y1, BAO, and D/H data. Mon. Not. R. Astron. Soc. 480, 3879–3888 (2018).

  11. Schutz, B. F. Determining the Hubble constant from gravitational wave observations. Nature 323, 310–311 (1986).

    Article  ADS  Google Scholar 

  12. Nissanke, S., Holz, D. E., Hughes, S. A., Dalal, N. & Sievers, J. L. Exploring short gamma-ray bursts as gravitational-wave standard sirens. Astrophys. J. 725, 496–514 (2010).

    Article  ADS  Google Scholar 

  13. Abbott, B. P. et al. A gravitational-wave standard siren measurement of the Hubble constant. Nature 551, 85–88 (2017).

    Article  ADS  Google Scholar 

  14. Abbott, B. P. et al. GW170817: observation of gravitational waves from a binary neutron star inspiral. Phys. Rev. Lett. 119, 161101 (2017).

    Article  ADS  Google Scholar 

  15. Abbott, B. P. et al. Multi-messenger observations of a binary neutron star merger. Astrophys. J. Lett. 848, L12 (2017).

    Article  ADS  Google Scholar 

  16. Guidorzi, C. et al. Improved constraints on H0 from a combined analysis of gravitational-wave and electromagnetic emission from GW170817. Astrophys. J. Lett. 851, L36 (2017).

    Article  ADS  Google Scholar 

  17. Mooley, K. P. et al. Superluminal motion of a relativistic jet in the neutron star merger GW170817. Nature 561, 355–359 (2018).

    Article  ADS  Google Scholar 

  18. Chen, H.-Y., Fishbach, M. & Holz, D. E. Precision standard siren cosmology. Nature 562, 545–547 (2018).

    Article  ADS  Google Scholar 

  19. Feeney, S. M. et al. Prospects for resolving the Hubble constant tension with standard sirens. Mon. Not. R. Astron. Soc. 476, 3861–3882 (2018).

    Article  ADS  Google Scholar 

  20. Mooley, K. P. et al. A mildly relativistic wide-angle outflow in the neutron-star merger event GW170817. Nature 554, 207–210 (2018).

    Article  ADS  Google Scholar 

  21. Alexander, K. D. et al. A decline in the X-ray through radio emission from GW170817 continues to support an off-axis structured jet. Astrophys. J. Lett. 863, L18 (2018).

    Article  ADS  Google Scholar 

  22. Margutti, R. et al. The binary neutron star event LIGO/Virgo GW170817 160 days after merger: synchrotron emission across the electromagnetic spectrum. Astrophys. J. Lett. 856, L18 (2018).

    Article  ADS  Google Scholar 

  23. LIGO Scientific Collaboration and Virgo Collaboration Properties of the binary neutron star merger GW170817. Phys. Rev. X 9, 011001 (2018).

    Google Scholar 

  24. Abbott, B. P. et al. Prospects for observing and localizing gravitational-wave transients with Advanced LIGO, Advanced Virgo and KAGRA. Living Rev. Relativity 21, 3 (2018).

    Article  ADS  Google Scholar 

  25. Fong, W., Berger, E., Margutti, R. & Zauderer, B. A. A decade of short-duration gamma-ray burst broadband afterglows: energetics, circumburst densities, and jet opening angles. Astrophys. J. 815, 102 (2015).

    Article  ADS  Google Scholar 

  26. Nissanke, S. et al. Determining the Hubble constant from gravitational wave observations of merging compact binaries. Preprint at (2013).

  27. Riess, A. G. et al. Milky Way Cepheid standards for measuring cosmic distances and application to Gaia DR2: implications for the Hubble constant. Astrophys. J. 861, 126 (2018).

    Article  ADS  Google Scholar 

  28. Vega-Ferrero, J., Diego, J. M., Miranda, V. & Bernstein, G. M. The Hubble constant from SN Refsdal. Astrophys. J. Lett. 853, L31 (2018).

    Article  ADS  Google Scholar 

  29. Feeney, S. M., Mortlock, D. J. & Dalmasso, N. Clarifying the Hubble constant tension with a Bayesian hierarchical model of the local distance ladder. Mon. Not. R. Astron. Soc. 476, 3861–3882 (2018).

    Article  ADS  Google Scholar 

  30. Weinberg, D. H. et al. Observational probes of cosmic acceleration. Phys. Rep. 530, 87–255 (2013).

    Article  ADS  MathSciNet  Google Scholar 

  31. Kelly, P. L. et al. Multiple images of a highly magnified supernova formed by an early-type cluster galaxy lens. Science 347, 1123–1126 (2015).

    Article  ADS  Google Scholar 

  32. Goobar, A. et al. iPTF16geu: a multiply imaged, gravitationally lensed type Ia supernova. Science 356, 291–295 (2017).

    Article  ADS  Google Scholar 

  33. Goldstein, D. A., Nugent, P. E., Kasen, D. N. & Collett, T. E. Precise time delays from strongly gravitationally lensed type Ia supernovae with chromatically microlensed images. Astrophys. J. 855, 22 (2018).

    Article  ADS  Google Scholar 

  34. Hallinan, G. et al. A radio counterpart to a neutron star merger. Science 358, 1579–1583 (2017).

    Article  ADS  Google Scholar 

  35. Ruan, J. J., Nynka, M., Haggard, D., Kalogera, V. & Evans, P. Brightening X-ray emission from GW170817/GRB 170817A: further evidence for an outflow. Astrophys. J. Lett. 853, L4 (2018).

    Article  ADS  Google Scholar 

  36. D’Avanzo, P. et al. The evolution of the X-ray afterglow emission of GW 170817/GRB 170817A in XMM-Newton observations. Astron. Astrophys. 613, L1 (2018).

    Article  ADS  Google Scholar 

  37. Dobie, D. et al. A turnover in the radio light curve of GW170817. Astrophys. J. Lett. 858, L15 (2018).

    Article  ADS  Google Scholar 

  38. Troja, E. et al. The outflow structure of GW170817 from late-time broad-band observations. Mon. Not. R. Astron. Soc. 478, L18–L23 (2018).

    Article  ADS  Google Scholar 

  39. Lamb, G. P. & Kobayashi, S. GRB 170817A as a jet counterpart to gravitational wave trigger GW 170817. Mon. Not. R. Astron. Soc. 478, 733–740 (2018).

    Article  ADS  Google Scholar 

  40. Lyman, J. D. et al. The optical afterglow of the short gamma-ray burst associated with GW170817. Nat. Astron. 2, 751–754 (2018).

    Article  ADS  Google Scholar 

  41. Gill, R. & Granot, J. Afterglow imaging and polarization of misaligned structured GRB jets and cocoons: breaking the degeneracy in GRB 170817A. Mon. Not. R. Astron. Soc. 478, 4128–4141 (2018).

    Article  ADS  Google Scholar 

  42. Resmi, L. et al. Low frequency view of GW 170817/GRB 170817A with the Giant Meterwave Radio Telescope. Astrophys. J. Lett. 867, 57 (2018).

    Article  Google Scholar 

  43. Nakar, E. & Piran, T. Implications of the radio and X-ray emission that followed GW170817. Mon. Not. R. Astron. Soc. 478, 407–415 (2018).

    Article  ADS  Google Scholar 

  44. Xie, X., Zrake, J. & MacFadyen, A. Numerical simulations of the jet dynamics and synchrotron radiation of binary neutron star merger event GW170817/GRB170817A. Astrophys. J. 863, 58 (2018).

    Article  ADS  Google Scholar 

  45. Gottlieb, O., Nakar, E. & Piran, T. The cocoon emission—an electromagnetic counterpart to gravitational waves from neutron star mergers. Mon. Not. R. Astron. Soc. 473, 576–584 (2018).

    Article  ADS  Google Scholar 

  46. Lazzati, D. et al. Late time afterglow observations reveal a collimated relativistic jet in the ejecta of the binary neutron star merger GW170817. Phys. Rev. Lett. 120, 241103 (2018).

    Article  ADS  Google Scholar 

  47. Sari, R., Piran, T. & Narayan, R. Spectra and light curves of gamma-ray burst afterglows. Astrophys. J. Lett. 497, L17–L20 (1998).

    Article  ADS  Google Scholar 

  48. Hotokezaka, K. & Piran, T. Mass ejection from neutron star mergers: different components and expected radio signals. Mon. Not. R. Astron. Soc. 450, 1430–1440 (2015).

    Article  ADS  Google Scholar 

  49. Foreman-Mackey, D., Hogg, D. W., Lang, D. & Goodman, J. emcee: the MCMC hammer. Publ. Astron. Soc. Pac. 125, 306–312 (2013).

    Article  ADS  Google Scholar 

  50. Finstad, D. et al. Measuring the viewing angle of GW170817 with electromagnetic and gravitational waves. Astrophys. J. Lett. 860, L2 (2018).

    Article  ADS  Google Scholar 

  51. Cantiello, M. et al. A precise distance to the host galaxy of the binary neutron star merger GW170817 using surface brightness fluctuations. Astrophys. J. Lett. 854, L31 (2018).

    Article  ADS  Google Scholar 

Download references


We are grateful to D. Brown, C. Hirata, V. Scowcroft, P. Shawhan, D. Spergel and H. Peiris for useful discussions. We thank the LIGO Scientific and Virgo Collaborations for public access to their data products. K.H. is supported by the Lyman Spitzer Jr. Fellowship at the Department of Astrophysical Sciences, Princeton University. E.N. and O.G. are supported by the I-Core center of excellence of the CHE-ISF. S.N. is grateful for support from NWO VIDI and TOP Grants of the Innovational Research Incentives Scheme (Vernieuwingsimpuls) financed by the Netherlands Organization for Scientific Research (NWO). The work of K.M. is supported by NASA through the Sagan Fellowship Program executed by the NASA Exoplanet Science Institute, under contract with the California Institute of Technology (Caltech)/Jet Propulsion Laboratory (JPL). G.H. acknowledges the support of NSF award AST-1654815. A.T.D. is the recipient of an Australian Research Council Future Fellowship (FT150100415).

Author information

Authors and Affiliations



K.H. carried out MCMC simulations with the synthetic models. E.N. and O.G. derived an analytic model and carried out hydrodynamic simulations to derive constraints on the observing angle. K.H. and K.M. analysed the posterior samples and calculated H0. G.H., K.P.M. and A.T.D. provided the input observational data. K.H., E.N., S.N. and G.H. wrote the paper. All co-authors discussed the results and provided comments on the manuscript.

Corresponding authors

Correspondence to K. Hotokezaka or E. Nakar.

Ethics declarations

Competing interests

The authors declare no competing interests.

Additional information

Peer review information: Nature Astronomy thanks Peter Nugent and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

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

Supplementary information

Supplementary Information

Supplementary Figs. 1–6 and Supplementary ref. 1.

Rights and permissions

Reprints and Permissions

About this article

Check for updates. Verify currency and authenticity via CrossMark

Cite this article

Hotokezaka, K., Nakar, E., Gottlieb, O. et al. A Hubble constant measurement from superluminal motion of the jet in GW170817. Nat Astron 3, 940–944 (2019).

Download citation

  • Received:

  • Accepted:

  • Published:

  • Issue Date:

  • DOI:

This article is cited by


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