Astronomers from the Australian National University (ANU) have unveiled a ground-breaking discovery of binary stars in the outer regions of the globular cluster 47 Tucanae, marking a world-first achievement that could reshape our understanding of how the Milky Way was built.
The breakthrough stems from the first public dataset released by the Vera C. Rubin Observatory’s ambitious Legacy Survey of Space and Time (LSST), an unprecedented 10-year effort to scan the southern sky every few nights and create a dynamic record of billions of stars and galaxies.
Lead researcher Dr Giacomo Cordoni explained that LSST will provide an extraordinary “movie of the universe,” allowing astronomers to track stars and galaxies as they change over time. The survey is set to unravel the histories of star clusters, galaxies, and the Milky Way itself, focusing particularly on globular clusters—some of the oldest, most tightly packed star systems known, each holding hundreds of thousands of stars.
Binary Stars Hold Clues to Galactic History
Within globular clusters, binary stars, pairs that orbit a shared center, are critical in charting a cluster’s evolutionary path.
These pairs interact energetically with neighbours, help determine cluster survival over billions of years, and can even produce exotic phenomena such as blue straggler stars.
Using data from Rubin’s Data Preview 1, the ANU team mapped binary stars in the outer regions of 47 Tucanae for the first time.
Strikingly, they found that binaries are about three times more prevalent in these outskirts than in the densely packed center, a region previously scrutinized with the Hubble Space Telescope.
Study co-author Professor Luca Casagrande emphasised that the discovery is remarkable given 47 Tucanae’s century-long history of study. The results suggest that disruption in the crowded cluster core destroys some binaries, while those in the quieter outer reaches survive, offering a glimpse of the cluster’s original population.
“This is a crucial piece of the puzzle of how globular clusters and the broader Milky Way evolved,” said Professor Helmut Jerjen. As Rubin Observatory continues its survey, it promises to deliver a comprehensive census of binary stars and other stellar systems, decisively testing theories of how galaxies and clusters formed.
The research will be published in PASA Letters, with an early copy available on arXiv.
