Study reveals the secret life of Lithium in Sun-like stars: created not just destroyed

Image showing many of the types of stars the study looked at, from young stars to old red giant stars. The research team  found Lithium in the fainter orange stars. Credit: ESA & NASA; Acknowledgement: E. Olszewski (U. Arizona) HST.

It is used in everything from medication to mobile phone batteries but where does Lithium come from?

Today a new international study involving a Monash astrophysicist and published in Nature Astronomy provides a fresh understanding of both how Lithium is made, and how it is destroyed.

Researchers studied the Lithium content of hundreds of thousands of Sun-like stars to understand how this element changes over time in stars.

“Lithium is quite a special element,” according to study co-author Dr Simon Campbell,  an ARC Future Fellow at the Monash University School of Physics and Astronomy.

“Our study challenges the idea that stars like the Sun only destroy Lithium through their lives,” he said.

“Our observations show that they actually create it 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."

Lithium is only one of three elements produced in the Big Bang. It gets destroyed very easily inside stars where it is too hot for it to survive, so stars generally reduce their Lithium content as they age.

Because it is such a sensitive element it is very useful for understanding stars, it acts as a tracer for what is happening inside stars.

To better understand this sensitive element, researchers used data from a world-leading  Australian star survey that is currently building a database of the chemical make-up of 1 million stars.

The survey, known as GALAH (Galactic Archaeology with the Hermes spectrograph), uses the largest optical telescope in Australia, the Australian Astronomical Telescope,  located in northern NSW.

“By looking at starlight we can determine what the stars are made of,” said Dr Campbell.

Dr Campbell’s contribution to the study involved computing detailed models of Sun-like stars.  His models show that our current theories about how stars evolve do not predict this Lithium production at all.

"Our findings will now compel stellar theorists to look at what physical processes are currently missing in their models, so Lithium can be produced in these stars", he said.

“Since the newly created Lithium will end up being blown off the star in stellar winds, it will also help us understand how much these stars enrich our Galaxy with Lithium, and eventually planets like Earth.”


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