Astronomers have been trying to determine the cosmic origins of the heaviest elements, like gold, for decades. Now, new research based on a signal uncovered in archival space mission data may point to a potential clue: magnetars, or highly magnetized neutron stars, CNN reported.

Scientists believe lighter elements such as hydrogen and helium, and even a small amount of lithium, likely existed early on after the big bang created the universe 13.8 billion years ago.

Then, exploding stars released heavier elements like iron, which became incorporated in newborn stars and planets. But the distribution of gold, which is heavier than iron, throughout the universe has posed a mystery to astrophysicists.

“It’s a pretty fundamental question in terms of the origin of complex matter in the universe,” said Anirudh Patel, lead author of the study published Tuesday in The Astrophysical Journal Letters and a doctoral student of physics at Columbia University in New York City, in a statement. “It’s a fun puzzle that hasn’t actually been solved.”