High levels of Lithium in evolved stars may be a mystery

New Delhi, Nov 30, : .

Scientists have discovered a clue to the mystery of the high abundance Lithium - a trace metal on Earth and a key component in rechargeable batteries – in some evolved starsAstronomers have known for more than 40 years that certain stars have an unusually high level of Lithium.

Since models of star evolution predict that the Lithium must have been destroyed by the stars hot plasma, it remains a mystery as to how and why this high amount of Lithium in red giants is about one percent.Deepak (who goes under a single name) is a researcher at the Indian Institute of Astrophysics, Bangalore.

This institute is an independent institute of the Department of Science & Technology, government of India.Professor Emeritus David L Lambert, a University of Texas at Austin Honorary Fellow, and Deepak from the Indian Institute of Astrophysics, Bangalore, confirmed for the first time that all lithium-rich stars have helium in the core.

In a paper published in MNRAS, the duo speculated that lithium production may be linked to the violent helium core flash "About forty years ago, a red-giant with an extraordinaryly high lithium abundance at its surface were discovered.This red giant was normal in all other aspects.

An early follow-up investigation into lithium among red giants revealed that only about one percent of sun-like red titans had a lithium-enriched surface.Deepak explained that we were intrigued by the processes that led to a 100-fold increase in lithium abundance in this extraordinary red giant, and the reasons behind this selective enrichment.The authors used observations from the 3.9 m Anglo Australian Telescope at Australias Astrophysical Observatory to conduct a large survey on the compositions red giants in Australia.GALAH, named after a common Australian bird, was able to collect approximately 500,000 stars with well-defined physical and chemical properties.

To determine if enrichment of lithium in red stars favors any particular mass or metallicity, the team separated GALAHs star into different mass and metality ranges.Next, they searched for lithium-rich titans within these groups.

This was the first time that this exercise was done on such a large scale across a wide range in mass and metallicity.It revealed the rare presence lithium-rich giants within all the Sun-like low mass stars.

They created virtual stars with different masses and metallicities and compared their properties to real stars from the GALAH Survey.These comparisons proved that all of the lithium-rich stars have helium in their cores.

The researchers also combined data about the interiors of stars with their lithium abundances to determine the origin of giant stars that are lithium-rich.They collected asteroseismic data, which is information about oscillations within stars interiors, for this study.

They discovered that all the lithium-rich stars of great size are burning helium at their cores.niv/pg #levels #Lithium #evolved #mystery #Delhi #Bangalore #Kannada #Bengaluru .