Astron. Astrophys. 576, L12 (2015)

Stars are chemical factories. Starting with hydrogen, stars produce all elements, light and heavy, within their cores and then blast them into space by supernovae. Depending on the amount of these various elements, it's possible to gauge the age of the progenitor star. Galactic archaeology depends on accurate measurements of the relative abundances of the light 'alpha' elements (mainly oxygen) and iron. In general, a high alpha to iron ratio, or [α/Fe], indicates an old star, as the lighter elements are released on a shorter timescale. But now Cristina Chiappini and co-workers have found a population of young stars with enhanced [α/Fe]. What does this mean?

First of all, Chiappini et al. used astroseismology for determining the ages of the stars. This involves the study of the pulsation frequencies of a star, in much the same way that seismologists can picture the core of the Earth without being able to look inside. In addition, the authors found that the stars lie near the inner Galactic disk, which suggests that the gas could be protected by the Galactic bar region — a kind of shelter from shocks in the spiral arms — and stay inert for longer.