article published yes Anna De Graaff author David J. Setton author Gabriel Brammer author Sam Cutler author Katherine A. Suess author Ivo Labbé author Joel Leja author Andrea Weibel author Michael V. Maseda author Katherine E. Whitaker author Rachel Bezanson author Leindert A. Boogaard author Nikko J. Cleri author Gabriella De Lucia author Marijn Franx author Jenny E. Greene author Michaela Hirschmann author Jorryt J Matthee author 7439a258-f3c0-11ec-9501-9df22fe067200000-0003-2871-127X Ian Mcconachie author Rohan P. Naidu author Pascal A. Oesch author Sedona H. Price author Hans Walter Rix author Francesco Valentino author Bingjie Wang author Christina C. Williams author JoMa department Within the established framework of structure formation, galaxies start as systems of low stellar mass and gradually grow into far more massive galaxies. The existence of massive galaxies in the first billion years of the Universe, as suggested by recent observations, seems to challenge this model, as such galaxies would require highly efficient conversion of baryons into stars. An even greater challenge in this epoch is the existence of massive galaxies that have already ceased forming stars. However, robust detections of early massive quiescent galaxies have been challenging due to the coarse wavelength sampling of photometric surveys. Here we report the spectroscopic confirmation with the James Webb Space Telescope of the quiescent galaxy RUBIES-EGS-QG-1 at redshift z = 4.90, 1.2 billion years after the Big Bang. Deep stellar absorption features in the spectrum reveal that the stellar mass of the galaxy of 1011 M⊙ formed in a short 200 Myr burst of star formation, after which star formation activity dropped rapidly and persistently. According to current galaxy formation models, systems with such rapid stellar mass growth and early quenching are too rare to plausibly occur in the small area probed spectroscopically with JWST. Instead, the discovery of RUBIES-EGS-QG-1 implies that early massive quiescent galaxies can be quenched earlier or exhaust gas available for star formation more efficiently than assumed at present. https://research-explorer.ista.ac.at/download/18631/19574/2025_NatureAstronomy_deGraaff.pdf application/pdfno Springer Nature2025 eng 2397-3366 39990236 00142034720000110.1038/s41550-024-02424-3 9280-292 De Graaff, Anna, David J. Setton, Gabriel Brammer, Sam Cutler, Katherine A. Suess, Ivo Labbé, Joel Leja, et al. “Efficient Formation of a Massive Quiescent Galaxy at Redshift 4.9.” <i>Nature Astronomy</i>. Springer Nature, 2025. <a href="https://doi.org/10.1038/s41550-024-02424-3">https://doi.org/10.1038/s41550-024-02424-3</a>. A. De Graaff <i>et al.</i>, “Efficient formation of a massive quiescent galaxy at redshift 4.9,” <i>Nature Astronomy</i>, vol. 9. Springer Nature, pp. 280–292, 2025. De Graaff A, Setton DJ, Brammer G, et al. Efficient formation of a massive quiescent galaxy at redshift 4.9. <i>Nature Astronomy</i>. 2025;9:280-292. doi:<a href="https://doi.org/10.1038/s41550-024-02424-3">10.1038/s41550-024-02424-3</a> A. De Graaff, D.J. Setton, G. Brammer, S. Cutler, K.A. Suess, I. Labbé, J. Leja, A. Weibel, M.V. Maseda, K.E. Whitaker, R. Bezanson, L.A. Boogaard, N.J. Cleri, G. De Lucia, M. Franx, J.E. Greene, M. Hirschmann, J.J. Matthee, I. Mcconachie, R.P. Naidu, P.A. Oesch, S.H. Price, H.W. Rix, F. Valentino, B. Wang, C.C. Williams, Nature Astronomy 9 (2025) 280–292. De Graaff A, Setton DJ, Brammer G, Cutler S, Suess KA, Labbé I, Leja J, Weibel A, Maseda MV, Whitaker KE, Bezanson R, Boogaard LA, Cleri NJ, De Lucia G, Franx M, Greene JE, Hirschmann M, Matthee JJ, Mcconachie I, Naidu RP, Oesch PA, Price SH, Rix HW, Valentino F, Wang B, Williams CC. 2025. Efficient formation of a massive quiescent galaxy at redshift 4.9. Nature Astronomy. 9, 280–292. De Graaff, Anna, et al. “Efficient Formation of a Massive Quiescent Galaxy at Redshift 4.9.” <i>Nature Astronomy</i>, vol. 9, Springer Nature, 2025, pp. 280–92, doi:<a href="https://doi.org/10.1038/s41550-024-02424-3">10.1038/s41550-024-02424-3</a>. De Graaff, A., Setton, D. J., Brammer, G., Cutler, S., Suess, K. A., Labbé, I., … Williams, C. C. (2025). Efficient formation of a massive quiescent galaxy at redshift 4.9. <i>Nature Astronomy</i>. Springer Nature. <a href="https://doi.org/10.1038/s41550-024-02424-3">https://doi.org/10.1038/s41550-024-02424-3</a> 186312024-12-08T23:01:56Z2025-05-19T14:01:21Z