The lithium content of omega Centauri. New clues to the cosmological Li problem from old stars in external galaxies

Understand

A discrepancy has emerged between the cosmic lithium abundance inferred by the WMAP satellite measurement coupled with the prediction of the standard big-bang nucleosynthesis theory, and the constant Li abundance measured in metal-poor halo dwarf stars (the so-called Spite plateau).

• Several models are being proposed to explain this discrepancy, involving either new physics, in situ depletion, or the efficient depletion of Li in the pristine Galaxy by a generation of massive first stars.
• The realm of possibilities may be narrowed considerably by observing stellar populations in different galaxies, which have experienced different evolutionary histories.
• The WCen stellar system is commonly considered as the remnant of a dwarf galaxy accreted by the Milky Way (MW).