The team found that blue stragglers are closely linked to binary star systems, in which two stars orbit one another. In such systems, one star can siphon material from its partner or merge with it entirely, gaining fresh fuel and shining more brightly and blue (effectively resetting its stellar clock).

However, these observations show that denser environments host less binaries, suggesting that in densely packed clusters, frequent close encounters between stars can break binaries apart before they have time to produce a blue straggler. In calmer environments, binaries survive and blue stragglers flourish.

“Crowded star clusters are not a friendly place for stellar partnerships,” explains Enrico Vesperini from Indiana University in the United States. “Where space is tight, binaries can be more easily destroyed, and the stars lose their chance to stay young.”

This discovery marks the first time that such clear and opposite-to-expectation relationships have been observed between blue straggler populations and their environments. It confirms that blue stragglers are a direct by-product of binary evolution and highlights how strongly a star’s surroundings can influence its life story.

“This work gives us a new way to understand how stars evolve over billions of years,” said Barbara Lanzoni, co-author of the study from the University of Bologna in Italy. “It shows that even star lives are shaped by their environment, much like living systems on Earth.”

By resolving individual stars in crowded clusters and observing them in ultraviolet light, Hubble was uniquely suited to uncovering this long-hidden pattern. The findings not only solve a long-standing astronomical mystery, but also open new paths for understanding how stars interact, age and sometimes find ways to start anew.

These results have been published today in Nature Communications.