A direct black-hole mass measurement in a little red dot at high redshift

Article A direct black-hole mass measurement in a little red dot at high redshift https://doi.org/10.1038/s41586-026-10579-4 Received: 30 August 2025 Accepted: 21 April 2026 Published online: 27 May 2026 Open access Check for updates Ignas Juodžbalis1,2 ✉, Cosimo Marconcini3,4, Francesco D’Eugenio1,2, Roberto Maiolino1,2,5, Alessandro Marconi3,4, Hannah Übler6, Jan Scholtz1,2, Xihan Ji1,2, Gareth C. Jones1,2, Michele Perna7, Santiago Arribas7, Jake S. Bennett8, Volker Bromm9, Andrew J. Bunker10, Stefano Carniani11, Stéphane Charlot12, Giovanni Cresci4, Pratika Dayal13,14, Eiichi Egami15, Andrew Fabian16, Kohei Inayoshi17, Yuki Isobe1,2,18, Lucy R. Ivey1,2, Sophie Koudmani19,20, Nicolas Laporte21, Boyuan Liu22, Jianwei Lyu15, Giovanni Mazzolari6, Stephanie Monty16, Eleonora Parlanti11, Pablo G. Pérez-González7, Brant Robertson23, Raffaella Schneider24, Debora Sijacki1,16, Sandro Tacchella1,2, Alessandro Trinca25, Rosa Valiante26, Marta Volonteri12, Joris Witstok27,28 & Saiyang Zhang29,30 Recent discoveries of faint active galactic nuclei (AGN) at the redshift frontier have revealed a plethora of broad Hα emitters with optically red continua, named little red dots (LRDs)1, which comprise 15–30% of the high-redshift broad-line AGN population2. Owing to their peculiar properties3–6, modelling LRDs with standard AGN scenarios has proven challenging. In particular, the validity of single-epoch virial mass estimates in determining the black-hole masses of LRDs has been called into question, with some models claiming that masses might be overestimated by up to two orders of magnitude7–10. Here we report a direct, dynamical black-hole mass measurement in a strongly lensed LRD at a redshift of 7.04. The combination of lensing with deep spectroscopic data reveals a rotation curve that is inconsistent with a nuclear star cluster, yet can be well explained by Keplerian rotation around a point mass of 50 million solar masses, consistent with virial black-hole mass estimates. The Keplerian rotation leaves little room for any stellar component in a host galaxy, as we conservatively infer MBH/M⁎ > 2 (where MBH is the black-hole mass and M⁎ is the stellar mass). Such a ‘naked’ black hole, together with its near-pristine environment11, indicates that this LRD is a massive black-hole seed caught in its earliest accretion phase. Abell 2744−QSO1 (hereafter QSO1) is a strongly lensed, triply imaged system, first discovered in the James Webb Space Telescope ( JWST) Near Infrared Camera imaging by ref. 12, whose redshift was confirmed to be z = 7.04 through Near Infrared Spectrograph (NIRSpec) prism spectroscopy13, which also revealed broad components in Hα and Hβ lines. The compactness and a red optical (rest frame) slope together with a blue ultraviolet (rest frame) slope classify it as a typical ‘little red dot’ (LRD)2,14. Further observations clearly spectrally resolved the broad- and narrow-line emission, and also detected line variability4,15,16, thereby robustly identifying QSO1 as hosting an accreting black hole (BH). On the basis of virial relations using broad-line widths and luminosities, a BH mass of about 4 × 107 M⊙ was estimated4,13,15. However, these results rest on the assumption that ‘virial relations’17 that are calibrated locally, are still applicable at z = 7. In this work, we provide a direct BH mass measurement in the high-redshift Universe, indeed illustrating that virial BH mass calibrations apply to this prototypical LRD. It is first interesting to note that, given the low narrow-line velocity dispersion in QSO115 (σN < 22 km s−1; Supplementary Information 1 Kavli Institute for Cosmology, University of Cambridge, Cambridge, UK. 2Cavendish Laboratory, University of Cambridge, Cambridge, UK. 3Università di Firenze, Dipartimento di Fisica e Astronomia, Florence, Italy. 4INAF - Arcetri Astrophysical Observatory, Florence, Italy. 5Department of Physics and Astronomy, University College London, London, UK. 6Max-Planck-Institut für extraterrestrische Physik, Garching, Germany. 7Centro de Astrobiología (CAB), CSIC-INTA, Madrid, Spain. 8Center for Astrophysics ∣ Harvard & Smithsonian, Cambridge, MA, USA. 9 Department of Astronomy, University of Texas at Austin, Austin, TX, USA. 10Department of Physics, University of Oxford, Oxford, UK. 11Scuola Normale Superiore, Pisa, Italy. 12Sorbonne Université, CNRS, Institut d’Astrophysique de Paris, Paris, France. 13Kapteyn Astronomical Institute, University of Groningen, Groningen, The Netherlands. 14Canadian Institute for Theoretical Astrophysics, University of Toronto, Toronto, Ontario, Canada. 15Steward Observatory, University of Arizona, Tucson, AZ, USA. 16Institute of Astronomy, University of Cambridge, Cambridge, UK. 17Kavli Institute for Astronomy and Astrophysics, Peking University, Beijing, China. 18Waseda Research Institute for Science and Engineering, Faculty of Science and Engineering, Waseda University, Tokyo, Japan. 19Centre for Astrophysics Research, Department of Physics, Astronomy and Mathematics, University of Hertfordshire, Hatfield, UK. 20St Catharine’s College, University of Cambridge, Cambridge, UK. 21Aix Marseille Université, CNRS, CNES, LAM (Laboratoire d’Astrophysique de Marseille), Marseille, France. 22Universität Heidelberg, Zentrum für Astronomie, Institut für Theoretische Astrophysik, Heidelberg, Germany. 23Department of Astronomy and Astrophysics, University of California, Santa Cruz, Santa Cruz, CA, USA. 24 Dipartimento di Fisica, ‘Sapienza’ Università di Roma, Rome, Italy. 25Como Lake Center for Astrophysics, DiSAT, Università degli Studi dell’Insubria, Como, Italy. 26INAF/Osservatorio Astronomico di Roma, Monte Porzio Catone, Italy. 27Cosmic Dawn Center (DAWN), Copenhagen, Denmark. 28Niels Bohr Institute, University of Copenhagen, Copenhagen, Denmark. 29 Department of Physics, University of Texas at Austin, Austin, TX, USA. 30Weinberg Institute for Theoretical Physics, Texas Center for Cosmology and Astroparticle Physics, University of Texas at Austin, Austin, TX, USA. ✉e-mail: Nature | Vol 653 | 28 May 2026 | 1017 Article Velocity (km s–1) (first moment) 0.1 0.1 0.9 3 centroid error 50 pc 15 10 35 0 30 –0.1 5 25 0 20 0.1 0.1 –5 15 –0.1 –0.005 2 0.1 0.5 Δy (″) Δy (″) –0.1 0 0.1 0.005 0 5 –0.1 –20 0.010 0 10 0 –15 –0.1 0.4 0.1 –10 0 Δy (″) 0.5 Δy (″) 0 0 0 –0.1 –0.5 1 Δy (″) 2R = 1.17 Residuals 40 0.6 Δy (″) Keplerian point mass model log(MBH/M() = 7.7 –0.1 0.8 0.7 0.1 0 n tatio –0.1 Δy (″) 0 n orie Δy (″) Data 0.1 20 e Slic 1.0 Velocity dispersion (km s–1) (second moment) Δy (″) Flux 0 0 –1 –0.1 –0.010 –0.1 0 0.1 Δx (″) –2 –0.1 0 Δx (″) 0.1 –0.1 0 0.1 Δx (″) Fig. 1 | Hα narrow-line emission and moment maps of QSO1. The top row shows the observed integrated narrow Hα flux, and the first and second moments of the flux distribution, which correspond to line-of-sight velocity and velocity dispersion, respectively. T (...truncated)