biostudies-literatureMaiolino REuropean Research Council59-63https://www.ebi.ac.uk/biostudies/studies/S-EPMC10917688biostudies-literatureUnknown627(8002)Several theories have been proposed to describe the formation of black hole seeds in the early Universe and to explain the emergence of very massive black holes observed in the first thousand million years after the Big Bang^1-3. Models consider different seeding and accretion scenarios^4-7, which require the detection and characterization of black holes in the first few hundred million years after the Big Bang to be validated. Here we present an extensive analysis of the JWST-NIRSpec spectrum of GN-z11, an exceptionally luminous galaxy at z = 10.6, revealing the detection of the [NeIV]λ2423 and CII*λ1335 transitions (typical of active galactic nuclei), as well as semi-forbidden nebular lines tracing gas densities higher than 10⁹ cm^-3, typical of tNatureA small and vigorous black hole in the early Universe.PMC10917688101040227695671Charlot SWillott CJChevallard JTacchella SBoyett KCurtis-Lake EDeCoursey CD'Eugenio FEisenstein DJWilliams CCCarniani SHainline KNWillmer CNAArribas SSandles LPerna MRodriguez Del Pino BBaker WMSun FScholtz JRawle TDJones GCCurti MHelton JMWitstok JLooser TJde Graaff AMaiolino RBunker ARobertson BFabian ACNelson EJShivaei IUbler HJi ZEgami EMaseda MVKumari NLaporte NfalseA small and vigorous black hole in the early Universe.Several theories have been proposed to describe the formation of black hole seeds in the early Universe and to explain the emergence of very massive black holes observed in the first thousand million years after the Big Bang^1-3. Models consider different seeding and accretion scenarios^4-7, which require the detection and characterization of black holes in the first few hundred million years after the Big Bang to be validated. Here we present an extensive analysis of the JWST-NIRSpec spectrum of GN-z11, an exceptionally luminous galaxy at z = 10.6, revealing the detection of the [NeIV]λ2423 and CII*λ1335 transitions (typical of active galactic nuclei), as well as semi-forbidden nebular lines tracing gas densities higher than 10⁹ cm^-3, typical of t2024-01-01T00:00:00Z2024 Mar2025-07-09T03:05:13.73Z2025-07-09T03:05:13.73ZS-EPMC109176883823294410.1038/s41586-024-07052-5