We have assembled all the observations of the 12C/13C ratio in field and cluster giants available in the literature. Using the HIPPARCOS parallaxes, we get constraints on the evolutionary status of our sample stars. We determine that 96% of low-mass stars do experience an extra-mixing process on the RGB and are then expected to destroy their 3He. While consistent "non-standard" stellar models are needed to explain the various chemical anomalies in low-mass RGB stars in order to obtain reliable 3He yields, we can already conclude that the very high percentage we get satisfies the galactic requirements for the evolution of the 3He abundance.
© European Southern Observatory (ESO) 1998
Online publication: July 27, 1998