First evidence of lithium found in exploding star solves mystery

For the first time, researchers have found evidence of the chemical element lithium in material ejected by an exploding star, and their discovery could help explain why so many younger stars appear to have this substance in greater-than-expected amounts.

In a paper in The Astrophysical Journal, Luca Izzo of the Sapienza University of Rome Department of Physics and the ICRANet (International Center for Relativistic Astrophysics) in Pescara, Italy, explained how they found the element by studying Nova Centauri 2013 at the ESO’s La Silla Observatory in Chile.

“Lithium is one of the elements produced during the Big Bang nucleosynthesis (BBN),” Izzo and co-authors Massimo Della Valle and Luca Pasquini told redOrbit via email. “It is an element easily destroyed by most astrophysical processes, indeed the lithium abundance observed in old stellar populations is a bit smaller than the value estimated from the BBN.”

“However, in younger stellar populations, the abundance of lithium can reach values larger up to one order of magnitude than the primordial one, so for many years the question about was: where does it come from the Lithium observed in young stars?” they added. “We have detected, for the first time, the presence of lithium in a nova star. This implies that nova systems (about 30 events per year in our galaxy) enrich the gas of the Milky Way through their ejecta.”

Solving the mystery of lithium abundance in young stars

As early as the 1970s, astrophysicists had hypothesized that lithium could be produced in a few astrophysical sources: novae and asymptotic giant branch (AGB) stars. In depth simulations of chemical enrichment of the galaxy demonstrated the novae were needed to explain the overabundance of lithium in young stellar populations.

However, prior to the detection of the element in Nova Centauri 2013 (V1369 Centauri), there was no evidence to support this hypothesis, Izzo’s said. Their discovery solves a long-standing puzzle regarding the chemical evolution of the galaxy, and shows that lithium-enriched stars will originate from the ejected gas, explaining their overabundance of the element.

Izzo noted that the discovery was a long-time coming for Della Valle and Pasquini, who have been searching for evidence of lithium in novae for well over than two decades. “This is the satisfying conclusion for a long search for them,” he told redOrbit, adding that the discovery “proves that you may need decades before a prediction is observationally validated.”

In a statement, Della Valle added that the lithium detection was “a very important step forward. If we imagine the history of the chemical evolution of the Milky Way as a big jigsaw, then lithium from novae was one of the most important and puzzling missing pieces. In addition, any model of the Big Bang can be questioned until the lithium conundrum is understood.”

(Image credit: ESO)