All-sky Precise Stellar Ages for Galactic and Stellar Archaeology

The ages of stars are hard to discern. Stellar ages are very important because the compositions of stars change with time. Many questions related to the origin of our own Milky Way Galaxy will be answered with better stellar ages and compositions. The research team has developed a procedure to discern ages for a type of stars called ``subgiants''. The research team will calculate precise ages and compositions for hundreds of thousands of subgiants. They will then use these results to the study the formation and evolution of our own Milky Way Galaxy. Students from Johns Hopkins University and the National Society of Black Physicists will be part of this effort. The research team will also work to put on planetarium shows at Boys & Girls Clubs of Metropolitan Baltimore. Stellar ages are difficult to precisely infer. Even the most careful analyses of stars with Kepler asteroseismology only provide model-dependent ages precise to no better than 10%. These imprecise ages are holding back the fields of Galactic and stellar archaeology. The problem is even more acute for metal-poor stars, of which there are few of sufficient apparent magnitude in the parts of the sky where 10% precision age inferences are in principle possible. The investigator will produce the first and largest all-sky catalog of stellar ages with 1% accuracy. This catalog will also include photospheric stellar parameters (i.e., effective temperature, surface gravity, and metallicity), fundamental stellar parameters (i.e., mass and age), and Galactic orbits. It will yield homogeneously inferred age--metallicity--orbit distributions for the thin disk, thick disk, and halo of the Milky Way. The relative ages of the thin disk, thick disk, and halo will reveal the physical processes responsible for their formation. In addition, it will enable the isolation of the oldest stars in the Milky Way at all metallicities. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.