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Production of lithium in stars

Topics Covered: Awareness in space.

Production of lithium in stars

A forty-year-old puzzle regarding the production of lithium in stars has been solved by Indian researchers.

What was the puzzle all about?

Stars, as per known mechanisms of evolution, actually destroy lithium as they evolve into red giants. Planets were known to have more lithium than their stars — as is the case with the Earth-Sun pair.

However, leading to a contradiction, some stars were found that were lithium-rich. 

  • This posed a puzzle — if stars do not produce lithium, how do some stars develop to become lithium rich?

So far, the planet engulfment theory was quite popular. For example, Earth-like planets may increase the star’s lithium content when they plunge into their star’s atmosphere when the latter become Red Giants.

Latest findings:

When stars grow beyond their Red Giant stage into what is known as the Red Clump stage, they produce lithium in what is known as a Helium Flash and this is what enriches them with lithium.

The study also challenges the present understanding of nucleosynthesis in stars.

What is the big bang nucleosynthesis (BBN)?

The Big Bang Nucleosynthesis 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.

  • It is the production of nuclei other than those of the lightest isotope of hydrogen during the early phases of the Universe. Primordial nucleosynthesisis believed by most cosmologists to have taken place in the interval from roughly 10 seconds to 20 minutes after the Big Bang.

Origin of Lithium:

It was first produced in the Big Bang, around 13.7 billion years ago when the universe came into being, along with other elements.

While the abundance of other elements grew millions of times, the present abundance of lithium in the universe is only four times the original [Big Bang] value.

It is actually destroyed in the stars.

  • The Sun, for instance, has about a factor of 100 lower amount of lithium than the Earth.



Prelims Link:

  1. About Lithium.
  2. Different stages in the evolution of a star.
  3. What is big bang nucleosynthesis (BBN)?
  4. What is a helium flash?

Sources: the Hindu.