Fossil magnetic fields protect Helium 3 in dying stars

Produced during primordial nucleosynthesis at the beginning of the Universe, ³He is also synthesized by nuclear fusion in the core of low-mass stars like our Sun. Its abundance should thus increase. But observations of Galactic H II regions have shown that it is not the case. Two french astronomers, Corinne Charbonnel and Jean-Paul Zahn, have recently suggested that it is thermohaline mixing that destructs ³He in giant stars, and that stabilizes its abundance in the Galaxy. This mechanism could explain other carbon, nitrogen and lithium anomalies found at the surface of most evolved low-mass stars and that remained unexplained so far.