Astronomers were looking deep into space with the help of two telescopes in Chile at Nova Centauri when they spotted something that could solve a big stellar mystery: lithium.

Nova Centauri is the brightest nova that we’ve been able to see this past century, and it is helping scientists understand how much lithium exists in stars after the substance was detected in material ejected by a nova for the first time, according to a Christian Science Monitor report.

Nova Centauri exploded in 2013, catching the eye of scientists who have been studying it at the European Southern Observatory (ESO). It’s a major finding that potentially solves a mystery in how the galaxy evolves chemically. The ESO said in a statement as reported by the Monitor that the finding was a “big step forward for astronomers” who are trying to understand the chemical makeup of stars in the Milky Way.

Using models that assume the Big Bang happened at around 13.8 billion years ago, astronomers can calculate the amount of lithium that should be found in a star, with older stars having less lithium and younger stars having more.

Lithium has now become a big player in scientists’ study of the universe and stellar evolution in particular.

It’s not the first time lithium has come on scientists’ radar. Back in 2012, they watched as a planet was sucked in by a red giant that contained a lot of lithium. Lower lithium levels in younger stars have long been proposed as something that could be explained by being blown out of a nova. But the first time that there was clear evidence of lithium in the nova to prove the hypothesis, the scientists found.