The galaxy UHZ1 hosts an X-ray-bright supermassive black hole seen 470 million years after the Big Bang, as NASA announced in 2023
UHZ1 (galaxy behind the cluster Abell 2744)· afirmado el 6 nov 2023 · fuente original
On 6 November 2023 NASA and the Center for Astrophysics (CfA) announced that Chandra and Webb had found the most distant black hole yet seen in X-rays, in the galaxy UHZ1, weighing an estimated 10 to 100 million suns. The team called it the best evidence yet that some black holes are born heavy, from collapsing gas clouds. The X-ray signal rested on a small number of photons, though. A reanalysis published in The Astrophysical Journal on 14 October 2026, and covered in the press on 15 November 2026, says the detection does not hold up once more Chandra data are added and that mid-infrared data from Webb show no sign of a buried active nucleus. The case would be settled by a robust, reproducible X-ray detection or independent signs of an active nucleus (in spectra or infrared data), or by limits that firmly rule out a black hole of the claimed power.
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NASA/CfA release: Chandra and Webb found a growing black hole of 10–100 million suns in UHZ1
The 6 November 2023 release says "over two weeks of observations with Chandra" showed X-ray-emitting superheated gas in UHZ1, "a trademark for a growing supermassive black hole", with lensing by Abell 2744 magnifying the signal about four times. It puts the mass at 10 to 100 million suns, based on the brightness and energy of the X-rays. Co-author Priyamvada Natarajan calls it "the first detection of an 'Outsize Black Hole'" and the best evidence yet that some black holes form from massive gas clouds.
cfa.harvard.eduNASA Telescopes Discover Record-Breaking Black Hole | Center for Astrophysics | Harvard & SmithsonianCambridge, MA -- Astronomers have discovered the most distant black hole yet seen in X-rays, using NASA telescopes. The black hole is at an early stage of growth that had never been witnessed before, where its mass is similar to that of its host galaxy. This result may explain how some of the first
Bogdán et al. (Nature Astronomy): an X-ray-luminous, heavily obscured quasar in UHZ1
The discovery paper (arXiv preprint, revised September 2023) reports Chandra detection of an X-ray-luminous black hole in the lensed galaxy UHZ1. It describes a heavily obscured quasar with a bolometric luminosity of about 5×10^45 erg/s and a black hole of roughly 10^7–10^8 solar masses, assuming accretion at the Eddington limit. The authors say this mass, comparable to the galaxy's stars, fits the theoretical picture of heavy black hole seeds.
arXiv.orgEvidence for heavy seed origin of early supermassive black holes from a z~10 X-ray quasarObservations of quasars reveal that many supermassive black holes (BHs) were in place less than 700 million years after the Big Bang. However, the origin of the first BHs remains a mystery. Seeds of the first BHs are postulated to be either light (i.e., $10-100~\rm{M_{\odot}})$, remnants of the firs
Goulding et al. (ApJ Letters): JWST/NIRSpec spectrum confirms the redshift at z ≈ 10.1
A spectrum from Webb's NIRSpec confirms UHZ1's distance spectroscopically (z ≈ 10.1), so the galaxy really is seen less than 500 million years after the Big Bang. That supports the distance part of the claim, not the black hole itself: according to the 2026 reanalysis, this spectrum showed neither broad lines nor high-ionization UV emission, which the original team attributed to heavy obscuration.
Zou et al. 2026 (ApJ): with all 2.2 Ms of Chandra data the hard X-ray excess reaches only 2.3–2.9σ
The team reanalysed all 2.2 Ms of Chandra imaging, including 0.95 Ms taken in 2023–2024 and not published before. Across all their data reductions, the 2–7 keV excess at UHZ1 reaches only 2.3–2.9σ, against the 4.2–4.4σ originally reported. In 100,000 random astrometric shifts, only 0.04% (original data) and 0.01% (full data) reached 4.2σ. The signal also did not grow with the extra exposure, as a steady source should. UHZ1 is undetected in all nine JWST/MIRI bands, which caps any buried AGN at L_bol < 1.3×10^45 erg/s. The authors conclude there is "no compelling evidence for a luminous obscured AGN" and describe UHZ1 as a low-mass, metal-poor, star-forming galaxy.
