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General-relativistic precession in a black-hole binary


The general-relativistic phenomenon of spin-induced orbital precession has not yet been observed in strong-field gravity. Gravitational-wave observations of binary black holes (BBHs) are prime candidates, as we expect the astrophysical binary population to contain precessing binaries1,2. Imprints of precession have been investigated in several signals3,4,5, but no definitive identification of orbital precession has been reported in any of the 84 BBH observations so far5,6,7 by the Advanced LIGO and Virgo detectors8,9. Here we report the measurement of strong-field precession in the LIGO–Virgo–Kagra gravitational-wave signal GW200129. The binary’s orbit precesses at a rate ten orders of magnitude faster than previous weak-field measurements from binary pulsars10,11,12,13. We also find that the primary black hole is probably highly spinning. According to current binary population estimates, a GW200129-like signal is extremely unlikely, and therefore presents a direct challenge to many current binary-formation models.

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Fig. 1: Precession frequency of GW200129.
Fig. 2: The magnitude and tilt of the spin of the larger black hole.
Fig. 3: Anatomy of GW200129.

Data availability

The posterior samples from the analyses performed in this work are available on Zenodo at Public documentation is available at


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We thank T. Dent, S. Ghosh, E. Hamilton, P. Kolitsidou, L. London and F. Ohme for discussions; and K. Riles for guidance during the internal LIGO review process. The authors were supported in part by Science and Technology Facilities Council (STFC) grant ST/V00154X/1 and European Research Council (ERC) Consolidator Grant 647839. Calculations were performed using the supercomputing facilities at Cardiff University operated by Advanced Research Computing at Cardiff (ARCCA) on behalf of the Cardiff Supercomputing Facility and the HPC Wales and Supercomputing Wales (SCW) projects. We acknowledge the support of the latter, which is part-funded by the European Regional Development Fund (ERDF) via the Welsh Government. In part, the computational resources at Cardiff University were also supported by STFC grant ST/I006285/1. We are also grateful for computational resources provided by LIGO Laboratory and supported by National Science Foundation Grants PHY-0757058 and PHY-0823459. This material is based on work supported by NSF’s LIGO Laboratory, which is a major facility fully funded by the National Science Foundation. This research has made use of data, software and/or web tools obtained from the Gravitational Wave Open Science Center (, a service of LIGO Laboratory, the LIGO Scientific Collaboration and the Virgo Collaboration. LIGO is funded by the US National Science Foundation. Virgo is funded by the French Centre National de Recherche Scientifique (CNRS), the Italian Istituto Nazionale della Fisica Nucleare (INFN) and the Dutch Nikhef, with contributions by Polish and Hungarian institutes. Plots were prepared with Matplotlib59, GWpy60 and PESummary61. Parameter estimation was performed with the LALInference37 and LALSimulation libraries within LALSuite62, as well as the BILBY63,64 and PBILBY41 libraries and the DYNESTY nested sampling package42. NumPy65, Scipy66 and Positive67,68 were used during the analysis.

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Authors and Affiliations



M.H. initiated and lead the study and writing of the text. C.H. and J.E.T. performed the parameter-estimation calculations on the detector data, and the synthetic injections. J.E.T. performed the mismatch calculations. V.R. and S.F. provided valuable input to the analysis; V.R. verified the PE results and S.F. produced Fig. 3. M.H., C.H., J.E.T., S.F. and V.R. all contributed to the interpretation of the results and writing the paper. Although they did not directly contribute to the results presented here, the other authors contributed to the LVK’s initial understanding of GW200129, which was the foundation of this work.

Corresponding author

Correspondence to Mark Hannam.

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The authors declare no competing interests.

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Nature thanks Michael Kesden and the other, anonymous, reviewer(s) for their contribution to the peer review of this work. Peer reviewer reports are available.

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Extended data figures and tables

Extended Data Fig. 1 Mismatches between waveform models and numerical-relativity waveforms.

Mismatches between three waveform models, and five waveforms from numerical-relativity simulations. The simulations were of binaries with mass-ratio 1:2, and varying values of the in-plane spin magnitude on the primary black hole, a1/m1, which is what drives precession. The dotted line shows the accuracy threshold assuming eight degrees of freedom, and the dashed-dotted line the threshold assuming only four degrees of freedom (see text for discussion). Only the NRSur7dq4 is well within the accuracy thresholds for GW200129.

Extended Data Fig. 2 Mismatches between the most accurate waveform model and those used in the LVK analysis.

Mismatches between theoretical signals (calculated using the NRSur7dq4 model) against the PhenomXPHM and SEOBNRv4PHM models. The model parameters are those recovered from our analysis of GW200129, but with a range of values of the primary spin magnitude a1/m1. We see that neither model meets the accuracy thresholds for GW200129 at high spins, but the better agreement of PhenomXPHM is consistent with it recovering results closer to those reported in this work.

Extended Data Fig. 3 Comparison between GW200129 results and those from a model-waveform injection.

One-dimensional posterior distributions for the primary black hole’s spin, a1/m1, and the binary’s mass ratio, q = m2/m1 ≤ 1, from a parameter-estimation analysis of GW200129 in raw detector data starting at 30 Hz, and an idealized zero-noise injection. The main results for the three-detector network (left) are broadly consistent between the real data and the injection. We also find in both the real data and the injection that analysis of a Hanford-Virgo-only analysis (middle) prefers equal-mass binaries and much weaker evidence for precession, while a Livingston-Virgo-only analysis (right) identifies an unequal-mass precessing binary; this can be explained by the lower SNR in Hanford (14.6, vs 21.2 in Livingston), which reduces the measurability of precession.

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Hannam, M., Hoy, C., Thompson, J.E. et al. General-relativistic precession in a black-hole binary. Nature 610, 652–655 (2022).

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