Helium flash in Sun-like stars produces lithium: study

The metallic element lithium can be generally produced in Sun-like stars after they go through a helium flash, according to a study by Chinese astronomers, published on Monday in the journal Nature Astronomy.

As one of the three elements generated during the Big Bang 13.7 billion years ago, lithium has been an important topic in studying the evolution of the universe and stars.

In previous studies, astronomers regarded lithium as fragile, and easily destroyed in the hot interiors of stars. They believed that lithium will gradually disappear in the evolution of stars.

However, some Sun-like stars, rich in lithium, have been discovered as observation technology improved. Where the lithium originated has been a puzzle for astronomers until now.

Researchers from the National Astronomical Observatories of Chinese Academy of Sciences (NAOC) found that the lithium content on Sun-like stars surges after a helium flash, based on data from China's spectroscopic survey telescope (known as LAMOST), the Australian stellar survey GALAH, and another star survey from a space mission known as GAIA.


A helium flash is a symbolic event in the evolution of Sun-like stars. In the late stage of a star's evolution, as helium accumulates at its core and causes its temperature and pressure to rise, the huge helium core is finally ignited, releasing enormous amounts of energy within minutes with a violent, nuclear combustion.

The researchers discovered that the lithium content of the observed stars is 200 times higher than theoretical predictions, on average, after a helium flash. This is an inevitable event in the evolution of Sun-like stars, indicating that they generally produce lithium after a helium flash.

The research to follow will focus on exploring the nuclear fusion related to the production of lithium, said Zhao Gang, leading researcher of the study. (Xinhua)



The paper can be accessed at https://www.nature.com/articles/s41550-020-1139-7