Sun-Like Stars Reveal The Secret Life Of Lithium

In contrast to theoretical predictions, stars can produce lithium after they become red giants, challenging our current understanding of the origins of lithium.

AsianScientist (Aug. 10, 2020) – Powering everything from mobile phones to electric vehicles, lithium has become essential for everyday life. In contrast to theoretical predictions that hot stars should destroy lithium, scientists have now found that stars can produce lithium as they age. These findings have been published in Nature Astronomy.

Lithium is one of the three elements produced during the Big Bang. It gets destroyed very easily inside stars where it is too hot for it to survive, so lithium content generally decreases as the stars age. Since lithium is such a sensitive element, it is very useful for understanding stars and can act as a tracer for what is happening inside the stars.

“Lithium is quite a special element,” said Dr. Yerra Bharat Kumar, first author of the study from the National Astronomical Observatories of Chinese Academy of Sciences (NAOC). “Our study challenges the idea that stars like the Sun only destroy lithium through their lives.”

To understand how lithium content changes over time in stars, the researchers used data from a huge Chinese stellar spectroscopic survey based on the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST), which is currently building a database of the spectra of ten million stars. This study also utilized data from Australian star survey known as GALactic Archaeology with HERMES (GALAH).

“By looking at starlight, we can determine what the stars are made of,” said Kumar. “Our observations show that they actually create lithium later in their lives, after they have swelled to become red giants. This means that the Sun itself will also manufacture lithium in the future,” he said.

These findings provide a fresh understanding of both how lithium is made and how it is destroyed, the authors said.

“Models show that our current theories about how stars evolve do not predict this lithium production at all. Thus, the study has created a tension between observations and theory,” Kumar said.

“Our findings will help us to better understand and model Sun-like stars,” said Professor Zhao Gang, the co-corresponding author of this study. “Since the newly created lithium will end up being blown off the star in stellar winds, it will also help us understand how these stars contribute to the lithium content of our Galaxy, and to planets like Earth.”

The article can be found at: Kumar et al. (2020) Discovery of Ubiquitous Lithium Production in Low-mass Stars.


Source: Chinese Academy of Sciences; Photo: NASA, ESA and T. Brown (STSCI).
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