Scientists have discovered clues to the mystery behind the abundance of lithium, a trace element on Earth and an important component of rechargeable batteries, on several evolved stars.
For over 40 years, astronomers have known that there is an unusual amount of lithium on the surface of a class of stars. A model of how a star evolves predicts that lithium must have been destroyed by the star’s high-temperature plasma, which is why it is behind the abundant lithium in about 1 percent of red giants. The process remains a mystery.
Mr. Deepak of the Indian Institute of Astronomical Physics (IIA) Bangalore, the Autonomous Institute of the Ministry of Science and Technology (DST) of the Government of India, David L. Lambert, Professor Emeritus of the University of Texas at Austin, and Honorary Fellow IIA Bangalore, Lithium For the first time, we have confirmed that all the abundant stars are burning helium in the core.They guessed in a paper published in a journal MNRAS Its lithium production is associated with intense helium core flash.
“About 40 years ago, a red giant with a very high amount of lithium was discovered on its surface. In all other respects, this red giant had a normal composition. Early follow-up on lithium in the red giant. It was shown that about 1% of sun-like red giants had a lithium-rich surface. With questions about the process that led to a 100-fold increase in the lithium abundance of this exceptional red giant. The reason why lithium was selectively enriched in 1% of red giants was intriguing to us, “explains Deepak.
The authors collected observations with the 3.9 m Anglo-Australian Telescope at the Australian Astronomical Observatory, based on a large-scale study of the composition of red giants in Australia at the Australian National University. The study GALAH, named after a common Australian bird, provided a collection of about 500,000 stars with well-determined physical and chemical properties, including the abundance of lithium.
To find out if the red giant’s lithium enrichment is beneficial for a particular mass and metal content, they divide the GALAH stars into different mass and metal content ranges, and within these groups lithium-rich giants. I searched for. For the first time on such a large scale and over a wide range of masses and metals, this exercise reveals the rare presence of lithium-rich giants in all low-mass stars such as the Sun.
They created virtual stars of varying mass and metal content and compared the properties of these virtual stars with those of real stars in the GALAH survey. These comparisons confirmed that all lithium-rich stars burn helium in their cores.
In another study, researchers combined information about the vibrations inside the star with the abundance of lithium to discover the origin of lithium-rich giants. For this study, they collected asteroseismic data on giant stars whose lithium abundance was measured (ie, information about vibrations inside the star). They found that all lithium-rich giants are burning helium in their core.
A few years ago, nuclear astrophysicists proposed a simple and short series of nuclear reactions involving collisions between two stable helium isotopes leading to stable lithium isotopes. This reaction is thought to occur during the first violent ignition of helium fusion in a hydrogen-depleted core, just before stable helium fusion begins in a red giant. The authors have adopted this idea and are calling on theoretical astrophysicists interested in the internal structure of red giants to provide a quantitative estimate of lithium production during ignition of helium fusion in red giants.
1) Deepak and David L. Lambert (2021), MNRAS, Volume 507, Issue 1, pp.205–224, https: //doi.org/10.1093/mnras/stab2022
2) Deepak and David L. Lambert (2021), MNRAS, Volume 505, Issue 1, pp. 642–648, https: //academic.oup.com/mnras/article/505/1/642/6256853
Contact Deepak (email@example.com) and Professor Lambert (firstname.lastname@example.org) for more information.
The Mystery Behind the Lithium Abundance of Some Evolved Stars Tracked – India Education | Latest Education News | Global Education News
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