It has long been believed that globular clusters or densely packed balls of several thousand stars came to be just when the universe came into existence — some 13 billion years ago. Most studies relating to the evolution of galaxies are based on this theory, but if the latest work from an international team of researchers is anything to go by, globular clusters formed much later, approximately four billion years after the universe’s birth.

The study revolves around binary star systems, stellar pairs that reside within these clusters, and their evolution. Scientists have long believed that these systems are just as old as their cluster and the researchers from the University of Warwick, U.K., leveraged this idea.

Binary Star Evolution within a Globular Cluster
Study reveals globular clusters might be much younger than the universe. Pictured, an artistic representation showcasing a binary star evolution within a globular cluster. Mark A. Garlick/University of Warwick

The research team developed a model called Binary Population and Spectral Synthesis or BPASS, in conjunction with the University of Auckland researchers, to predict the age of the star system so that the actual age of the clusters could also be determined. Then, they took traces of chemical elements found in the light from ancient binary star populations as well as their evolutionary processes into account to run the model.

The University of Warwick, in a release, noted that as part of the evolutionary process, two stellar bodies forming a binary star system interact. One grows into a giant star, while the other smaller one exerts a gravitational force onto its counterpart and strips its atmosphere, with elements like hydrogen and helium, away.

That said, taking all these factors into account, the new models predicted the age of binary star systems and revealed that the cluster they were a part of was nine billion years old, much younger than what previous models had suggested.

"It's important to note that there is still a lot of work to do — in particular looking at those very nearby systems where we can resolve individual stars rather than just considering the integrated light of a cluster — but this is an interesting and intriguing result,” Elizabeth Stanway, the lead author of the work, said in a statement.

The finding not just reveals old stellar populations in the cosmos might be less ancient than previously thought but also changes our understanding of galactic formation and evolution.

"If true, it changes our picture of the early stages of galaxy evolution and where the stars that have ended up in today's massive galaxies, such as the Milky Way, may have formed,” Stanway added. “We aim to follow up this research in future, exploring both improvements in modeling and the observable predictions which arise from them."

More than a hundred globular star clusters are known to exist within the boundaries of the Milky Way itself. The study titled “Reevaluating Old Stellar Populations” was published May 24 in the Monthly Notices of the Royal Astronomical Society