Indian Researchers Uncover Chemical Secrets of Ageing Stars

Researchers from the Indian Institute of Astrophysics have made a significant discovery regarding the chemical compositions of ageing stars, particularly focusing on red giant stars. Utilizing the ground-based Himalayan Chandra Telescope and leveraging archival data from observatories in Chile, France, and the United States, the team has revealed an unexpected chemical link during the late stages of stellar evolution.

The study aimed to measure the abundance of helium in these stars, a task complicated by the fact that cooler stars, such as our Sun, do not reach the temperatures necessary to excite helium and produce observable spectral lines. To address this, the researchers developed a complex methodology that first involved observing atomic and molecular spectral lines of magnesium. This data was then used to ascertain the hydrogen abundance, which is critical since hydrogen and helium exist in a relative abundance. A reduction in hydrogen abundance correlates with an increase in helium. The departure from expected hydrogen values allowed the scientists to derive the helium abundance accurately.

In a groundbreaking revelation, the researchers found that red giants rich in helium also exhibited high levels of lithium. This marks the first study of photospheric helium abundance in both normal and lithium-rich red giants. The lithium enrichment was notably identified in helium-rich red giants across various phases of stellar evolution.

Insights from the Research

The findings have been documented in a paper published in The Astrophysical Journal. Lead author BP Hema stated, “We applied this method to a sample of cool giant stars to study the correlation between lithium and helium abundances. This sample, consisting of 18 red giant stars and 2 super giant stars, was primarily studied using high-resolution spectra obtained from the Himalayan Chandra Telescope in Hanle, Ladakh, along with data from various international archives.”

Co-author Gajendra Pandey emphasized the significance of their results, noting, “All the helium-enhanced red giants were found to be super-lithium rich, with the exception of the super-giant star. However, not all lithium-rich giants are helium-enhanced. This suggests that photospheric helium enrichment is often accompanied by lithium enrichment in giants, as we had envisaged.”

The implications of this research extend beyond the specific findings, offering new insights into the chemical evolution of stars and enhancing our understanding of stellar life cycles. As astronomers continue to unravel the complexities of these celestial bodies, studies like this one underscore the intricate relationships between different chemical elements and the processes governing stellar evolution.

As the field of astrophysics advances, the collaboration among international observatories is proving vital for expanding knowledge and fostering new discoveries. This research not only contributes to our understanding of the cosmos but also exemplifies the importance of interdisciplinary cooperation in the quest to decipher the universe’s mysteries.