New Delhi, November 30 (SocialNews.XYZ) Scientists have found a clue to the mystery behind the high abundance of lithium – a trace element on Earth and a key component in rechargeable batteries – in some developed stars.
For more than four decades, astronomers have known that a class of stars has an abnormal amount of lithium on their surface. The cause and processes behind the high abundance of lithium in about one percent red giants have remained a puzzle, as the models of how stars evolve predict that lithium must have been destroyed in the star’s hot plasma.
Deepak (who goes by a single name) from the Indian Institute of Astrophysics (IIA), Bangalore, an autonomous institute under the Department of Science & Technology (DST), Government of India, and Professor Emeritus David L Lambert from the University of Texas at Austin and a honorary fellow from IIA Bangalore, has for the first time confirmed that all the lithium-rich stars burn helium in their core. In their paper published in the journal MNRAS, the duo have speculated that lithium production is linked to the violent helium-core flash.
“About four decades ago, a red giant with extraordinarily high lithium abundance was discovered on the surface. In all other respects, this red giant was of normal composition. Early follow-up study of lithium among red giants showed that only about one percent of sun-like reds giants had a lithium-enriched surface The questions of processes that led to a 100 times greater amount of lithium in this unusual red giant and the reason behind this selective enrichment of lithium in the one percent red giants fascinated us, “Deepak explained.
The authors drew on a large study of the composition of red giants conducted in Australia at the Australian National University with observations collected on the 3.9 m Anglo-Australian telescope at the Australian Astrophysical Observatory. The GALAH study – named after an ordinary Australian bird – yielded a collection of about 500,000 stars with well-defined physical and chemical properties, including abundance of lithium.
To find out if the enrichment of lithium in red giants favors a particular mass and metallicity, they separated GALAH stars into different mass and metallicity regions and then searched for lithium-rich giants among these groups. This exercise, performed for the first time on such a large scale and across a wide range of mass and metallicity, reveals the rare presence of lithium-rich giants in all the sun-like low-mass stars.
They created virtual stars of different mass and metallicity and compared the properties of these virtual stars with the real stars from the GALAH study. These comparisons confirmed that all the lithium-rich stars burn helium in their core.
In a separate study, the researchers combined information about oscillations in the interior of stars with their lithium abundance to find the origin of lithium-rich giant stars. For this study, they collected astero-seismic data (ie information on oscillations in the interior of stars) for giant stars with measured lithium deposits. They found that all the lithium-rich giant stars burn helium in their core.