Blue Stragglers are linked to binary systems, a Hubble study suggests.

Hubble observations of 3,419 blue straggler stars across 48 globular clusters show a higher blue straggler frequency in lower-density regions, and the fraction of binary systems in a cluster correlates with blue straggler counts.

Blue straggler stars are hotter, bluer members of old star clusters that appear younger than their cluster-mates. For decades researchers have debated whether these stars gain mass through direct stellar collisions or by accreting mass from a companion in a binary system. A team used the Hubble Space Telescope to compile the largest catalogue of blue stragglers yet, identifying 3,419 such stars in 48 galactic globular clusters. The study, led by Francesco Ferraro and published in Nature Communications, examines how cluster environment relates to blue straggler formation and survival. Key findings: - The survey identified 3,419 blue stragglers within 48 galactic globular clusters using Hubble data. - Blue straggler specific frequency decreases in high-density, high-collision-rate cluster environments compared with lower-density regions. - The fraction of binary systems hosted by a cluster correlates with the blue straggler specific frequency, supporting a binary-related origin. - The authors note that the observed correlations alone are not irrefutable proof of a physical connection, but binary patterns reproduce the BSS trends while other sub-populations do not. - Lead author Francesco Ferraro (University of Bologna) and co-authors including Enrico Vesperini and Barbara Lanzoni emphasize that environmental conditions affect binary survival and thus blue straggler populations. Summary: The study strengthens the case that many blue stragglers gain mass via interactions in binary systems and that low-density cluster environments better preserve binaries and their by-products. Undetermined at this time.