Lithium is an element with atomic number 3, symbol Li. The most abundant Isotope, atomic weight 7, is stable, and one more isotope, atomic weight 6 is also stable.
The Sun shows a lower Abundance of lithium than expected from big bang Nucleosynthesis, which was long a mystery, i.e., the Solar Lithium Problem. It burns at a Temperature less than Hydrogen burning, and it is believed that young stars continue mixing their constituents sufficiently long that the lithium is burned in the star's interior early in the star's life.
Brown Dwarf (BD)