In the realm of energy journalism, it’s crucial to stay abreast of scientific research that could potentially impact the energy sector. Today, we delve into a recent study that explores the abundance of lithium in certain types of stars and its implications for stellar evolution. The research was conducted by Ramiro de la Reza, Felix Llorente de Andrés, Emilio J. Alfaro, and Carolina Chavero, all affiliated with the Instituto Nacional de Astrofísica, Óptica y Electrónica in Mexico.
The study focuses on lithium-rich (Li-rich) giant stars with very low metallicities, a topic that has remained largely unexplored until now. The researchers utilized two extensive catalogues from the LAMOST (Large Sky Area Multi-Object Fiber Spectroscopic Telescope) survey, which provided data on field, low-mass giant stars with metallicities ranging from -4.0 to -1.0. These stars are divided into two groups: Li-rich and Li-poor.
The scarcity of stars with metallicities lower than -3.0 means that only three Li-rich red giant branch (RGB) stars are known in this regime. However, for metallicities greater than -2.5, the researchers detected giants across the horizontal branch (HB) and asymptotic giant branch (AGB) stages with lithium abundances up to 6.15 dex. Notably, some of these stars exhibited infrared (IR) excesses, indicative of mass loss and a recent episodic lithium-enrichment process. This process is likely related to the Cameron-Fowler mechanism, which involves the formation of new lithium-7 (7Li) isotopes.
The researchers identified three lithium thresholds based on these IR excesses: about 1.5 dex for RGB stars, about 0.5 dex for HB stars, and about -0.5 dex for AGB stars. These thresholds establish a new criterion to characterize Li-rich giants. The study also revealed that stars with IR excesses are distributed across most metallicity values, suggesting that the Cameron-Fowler mechanism is at work throughout a significant portion of the Galaxy’s evolutionary history.
In addition to studying lithium abundance, the researchers investigated stellar rotations in metal-poor giant stars. They found that a plateau appears for velocities greater than 40 km/s, extending up to near 90 km/s, with lithium abundances ranging from 1.02 to 1.82 dex. Among Li-rich giants with rotational velocities (v sin i) greater than 40 km/s, the researchers observed that increasing rotation is correlated with decreasing metallicity from -1.0 to -2.5. The presence of RGB and HB Li-rich giants with rotations up to 90 km/s suggests that stellar models must account for extended helium-3 (3He) reservoir lifetimes as a source of 7Li. The velocity around 40 km/s appears to be a new critical value in this context.
This research, published in the journal Astronomy & Astrophysics, provides valuable insights into the processes governing lithium enrichment and stellar rotation in metal-poor giant stars. While the direct implications for the energy sector may not be immediately apparent, understanding the fundamental processes of stellar evolution can contribute to our broader knowledge of the universe and the elements that comprise it. This knowledge can, in turn, inform the development of new technologies and materials that could benefit various industries, including energy.
As we continue to explore the cosmos, studies like this one remind us of the interconnectedness of scientific disciplines and the potential for unexpected discoveries to shape our understanding of the world around us. In the energy sector, staying informed about these advancements can help us anticipate and adapt to the challenges and opportunities that lie ahead.
This article is based on research available at arXiv.