Quasars are the most luminous non-transient objects known and as a result they enable studies of the Universe at the earliest cosmic epochs. Despite extensive efforts, however, the quasar ULAS J1120 + 0641 at redshift z = 7.09 has remained the only one known at z > 7 for more than half a decade1. Here we report observations of the quasar ULAS J134208.10 + 092838.61 (hereafter J1342 + 0928) at redshift z = 7.54. This quasar has a bolometric luminosity of 4 × 1013 times the luminosity of the Sun and a black-hole mass of 8 × 108 solar masses. The existence of this supermassive black hole when the Universe was only 690 million years old—just five per cent of its current age—reinforces models of early black-hole growth that allow black holes with initial masses of more than about 104 solar masses2,3 or episodic hyper-Eddington accretion4,5. We see strong evidence of absorption of the spectrum of the quasar redwards of the Lyman α emission line (the Gunn–Peterson damping wing), as would be expected if a significant amount (more than 10 per cent) of the hydrogen in the intergalactic medium surrounding J1342 + 0928 is neutral. We derive such a significant fraction of neutral hydrogen, although the exact fraction depends on the modelling. However, even in our most conservative analysis we find a fraction of more than 0.33 (0.11) at 68 per cent (95 per cent) probability, indicating that we are probing well within the reionization epoch of the Universe.
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We thank D. Ossip for support with the FIRE echellette observations and A. Stephens for help preparing the GNIRS observations. This work is based on data collected with the Magellan Baade telescope, the Gemini North telescope (programme GN-2017A-DD-4), the Large Binocular Telescope and the IRAM/NOEMA interferometer. We are grateful for the support provided by the staff of these observatories. We acknowledge the use of the UKIDSS, WISE and DECaLS surveys.
The authors declare no competing financial interests.
Reviewer Information Nature thanks D. Mortlock 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.
Extended data figures and tables
The red lines represent the continuum used in the main text, which was constructed by averaging SDSS DR12 quasars with similar C iv properties (equivalent widths and blueshifts) to those observed in J1342 + 0928 (see Fig. 3). The blue lines are 100 random draws of PCA-reconstructed intrinsic emission, as described in Methods. In both cases, the mean intrinsic spectrum is shown as a thick line. The vertical dashed line shows the Lyα wavelength. The PCA-reconstructed spectrum has stronger emission around the Lyα line than does the SDSS-matched reconstructed emission. The dotted line is the mean SDSS quasar from ref. 29, which has a much stronger Lyα line than that of any of our continuum models of J1342 + 0928.
a, Same as Fig. 3b, but showing 100 realizations of PCA-predicted intrinsic emission (blue) and damping-wing model (green) draws from the posterior PDF of model B (see Methods for details). Model B masks absorption systems only redwards of the Lyα line (pale blue) because this model takes into account the internal absorption in the proximity zone, which explains the larger scatter bluewards of the Lyα line (dashed vertical line). b, The marginalized posterior PDF of . The 50th percentile is and the 16th–84th (2.5th–97.5th) percentile interval is 0.45–0.87 (0.22–0.98).
a, Model B. b, Model C. Model B applied to continuum 1 yields the most conservative distribution of our analyses. Even in this case, a significantly neutral Universe with at the 2σ level is implied.
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Bañados, E., Venemans, B., Mazzucchelli, C. et al. An 800-million-solar-mass black hole in a significantly neutral Universe at a redshift of 7.5. Nature 553, 473–476 (2018). https://doi.org/10.1038/nature25180
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