Context: Recently, the researchers at the Indian Institute of Astrophysics (IIA) have discovered hundreds of Lithium (Li) rich giant stars which indicate that lithium is being produced in the stars and accounts for its abundance in the interstellar (between stars) medium.

About Lithium-rich Giant Stars

• The research indicates that Lithium is being produced in the stars and accounts for its abundance in the interstellar medium.
• The researchers have also associated such Lithium enhancement with central Helium-burning stars, also known as red clump giants, thereby opening up new vistas in the evolution of the red giant stars.
• Lithium (Li) is one of the three primordial elements, apart from Hydrogen and Helium (He), which is produced in the big bang nucleosynthesis (BBN) whose models predict primordial Li abundance.
• The present measurement of Lithium in the interstellar medium and very young stars is about 4 times more than the primordial value.
• The stars are considered as 'Lithium sinks'.
• The original Lithium, with which stars are born, only gets depleted over stars’ life-time as Li burns at relatively very low temperatures of about 2.5X106 K – a range which is easily encountered in stars.

Significance of this Discovery

• Researchers had discovered a number of super Li-rich giants which have Li quantity which is equal to or in some cases, more than 10 times the present value, A(Li) =3.2 dex ( measured in logarithmic scale relative to hydrogen).
• They showed for the first time that the Li enhancement in giants is associated only with central Helium-burning stars, which are also known as red clump giants.
• The discovery will help to eliminate many proposed theories such as planet engulfment or nucleosynthesis during the red giant evolution in which helium at the center is not burning.

About Big Bang Nucleosynthesis

• In physical cosmology, Big Bang nucleosynthesis (or primordial nucleosynthesis) refers to the production of nuclei other than H-1, the normal, light hydrogen, during the early phases of the universe, shortly after the Big Bang.
• It is believed to be responsible for the formation of hydrogen (H-1 or simply H), its isotope deuterium (H-2 or D), the helium isotopes He-3 and He-4, and the lithium isotope Li-7.
• Big Bang nucleosynthesis begins about one minute after the Big Bang, when the universe has cooled enough to form stable protons and neutrons, after baryogenesis.
• It is the leading explanation about how the universe began. At its simplest, it says that the universe started with a small singularity and then inflated over the next 13.8 billion years to the cosmos currently observed.
• The Universe's light-element abundance is another important criterion by which this theory is verified.
• It is now known that the elements observed in the Universe were created in either of two ways.
• Light elements (namely deuterium, helium, and lithium) were produced in the first few minutes of the Big Bang, while elements heavier than helium are thought to have their origins in the interiors of stars which formed much later in the history of the Universe.
• The theory predicts that roughly 25% the mass of the Universe consists of Helium. It also predicts about 0.01% deuterium, and even smaller quantities of lithium.