Asteroseismology is a powerful method for determining fundamental properties of stars .
We report the first application to a metal-poor object , namely the subgiant star \nu Ind .
We measured precise velocities from two sites , allowing us to detect oscillations and infer a large frequency separation of \Delta \nu = 24.25 \pm 0.25 \mu Hz .
Combining this value with the location of the star in the H-R diagram and comparing with standard evolutionary models , we were able to place constraints on the stellar parameters .
In particular , our results indicate that \nu Ind has a low mass ( 0.85 \pm 0.04 M _ { \sun } ) and is at least 9 Gyr old .