J/A+A/707/A111ivo://CDS.VizieR/J/A+A/707/A111CDSTomasetti E.Chiappini C.Nepal S.Moresco M.Lardo C.Cimatti A.,Anders F.Queiroz A.B.A.Limberg G.2026-04-02T06:28:33Z2026-03-05T08:36:15ZCDS support team

CDS, Observatoire de Strasbourg, 11 rue de l'Universite, F-67000 Strasbourg, France

cds-question@unistra.frmilky-way-galaxystellar-agesstellar-massesvisible-astronomyIn this work, we exploit the most robust, old, and cosmology-independent age estimates of individual stars from Gaia DR3 to place a lower bound on the age of the Universe, t_U. These constraints can be used as an anchor point for any cosmological model, providing an upper limit to the Hubble constant H_0_. We consider the stellar age catalog of Nepal et al. (2024A&A...688A.167N), selecting 3000 of the oldest and most robustly measured main sequence turn-off (MSTO) and subgiant branch (SGB) stars, with ages older than 12.5Gyr and associated uncertainty below 1Gyr. Stellar ages are derived via isochrone fitting using the Bayesian code StarHorse, spanning the uniform range 0-20Gyr, not considering any cosmological prior knowledge on t_U_. Applying a conservative cut in the Kiel diagram, strict quality cuts on both stellar parameters and posterior probability distribution shapes, and filtering out potential contaminants, we isolate a final sample of 160 bona-fide stars, representing the most numerous sample of precise and reliable MSTO and SGB stars ages available to date. The age distribution of the final sample peaks at 13.6+/-1.0(stat)+/-1.4(syst)Gyr. Assuming a maximum formation redshift for these stars of z_f_=20, corresponding to a formation delay of ~0.2Gyr, we obtain a lower bound on t_U_ of t_U_>=13.8+/-1.0 (stat) +/- 1.4(syst)Gyr. Considering the 10^th^ percentile of the posterior probability distributions of the individual stars, we find that, at 90% CL, 70 stars favour t_U_>13Gyr, while none exceeds 14.1Gyr. For this upper envelope to fall below 13Gyr, a shift of nearly the full systematic error budget would be required, indicating that such low values are only attainable under very peculiar assumptions. This work presents the first statistically significant use of individual stellar ages as cosmic clocks, opening a new, independent approach for cosmological studies. While this analysis represents already a significant step forward, future Gaia data releases will enable even larger and more precise stellar samples, further strengthening these constraints.2026A&A...707A.111Thttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/707/A111CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toI/355 : Gaia DR3 Part 1. Main source (Gaia Collaboration, 2022)I/354 : StarHorse2, Gaia EDR3 photo-astrometric distances (Anders+, 2022)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/707/A111https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/707/A111http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/707/A111https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/707/A111https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/707/A111http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/707/A111GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/A+A/707/A111/tabled1 (Star ID, age and mass)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/A+A/707/A111/tabled1?https://vizier.iucaa.in/viz-bin/conesearch/J/A+A/707/A111/tabled1?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/A+A/707/A111/tabled1?GETtext/xml+votable180.050000true137.291036415.75961220.0055555555555555566/301 1044 1058 1586 3080 4183 4318 4829 4963 5042 5617 5659 5757 5929 6459 6962 7162 8324 9067 9190 9285 9292 9463 9970 10340 10396 10724 11031 11148 11200 11587 11590 11684 12458 13371 14824 14897 14918 14937 14964 14972 15107 16384 16597 16658 16689 16704 16730 16983 17265 17471 17552 17757 18001 18384 18443 19681 20540 20638 22615 22750 22839 22894 22998 23179 23320 23508 24240 24605 24674-24675 25074 25108 25126 25543 26205 27360 27378 27522 27822 28522 28748 29238 29302 29855 30005 30046 30154 31252 31269 31544 31563 32486 33022 33028 33050 33103 33208 33242 33647 33669 33823 34103 34217 34224-34225 34373 34403 34471 34537 35226 35334 35686 35894 36157 36215 36288 36422 36951 37381 37383 37412 37439 37513 37600 38161 38206 38751 38865 39539 39808 39875 40116 40147 40330 40745 40890 41177 41180 41256 42010 44156 44184 44305 44418 44500 44905 44919 45041 45179 45334 45371 45417 45458 45541 45559 45563 45565 45623 45722 45846 45853 45892 45938 46005 46096 46148-46149 46228 46440 46504 46642 46739 47356-47357 47362 47601 47734 48028 48195 48396 48417 48452 48501 48716https://cdsarc.cds.unistra.fr/viz-bin/moc/J/A+A/707/A111?format=asciiOpticaldefaultJ/A+A/707/A111/tabled1Star ID, age and massrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintGaiaDR3Gaia DR3 source idmeta.id;meta.mainAge[12.53/17.38] 50th percentile of marginalized StarHorse age PDFGyrtime.agefloate_Age[0.46/0.99] 0.5*(84th-16th) percentile of marginalized StarHorse age PDFGyrstat.error;time.agefloatMass[0.76/0.98] 50th percentile of marginalized StarHorse mass PDFsolMassphys.massfloate_Mass[0.01/0.03] 0.5*(84th-16th) percentile of marginalized StarHorse mass PDFsolMassstat.error;phys.massfloat_RAPositions from Gaia DR3 (right ascension part)degpos.eq.ra;meta.main_DEPositions from Gaia DR3 (declination part)degpos.eq.dec;meta.main