Indian Astronomers Observe Active Formation of a Blue Straggler Star in Collinder 261

Scientists from the Indian Institute of Astrophysics (IIA) and international partners have directly observed a Blue Straggler Star (BSS) gaining mass from a companion. The discovery provides concrete evidence for the long‑debated theory that BSSs form through mass transfer in binary systems. Key Developments The binary system TIC 327546480 lies in the old open cluster Collinder 261 . High‑precision light curves from TESS and radial‑velocity data from the Very Large Telescope (VLT) revealed ongoing mass transfer. The system is semidetached ; the less massive star overflows its Roche lobe and feeds the BSS. Strong X‑ray emission confirms accretion of material onto the BSS. Important Facts The BSS has a mass of 1.67 M☉ and rotates at 69.55 km s⁻¹ . Its companion weighs about 0.32 M☉ . The orbital period is 2.11 days with a mass‑ratio of ~0.19. Evolutionary models suggest mass transfer began 5.46 billion years ago and continues today, while the host cluster is ~ 7 billion years old . UPSC Relevance Understanding BSS formation links to broader themes in stellar evolution and the dynamics of star clusters, topics covered in GS‑3. The collaborative nature of the research, involving Indian institutes (IIA, IUCAA, Gauhati University) and foreign agencies (ESO, INAF, University of North Florida), illustrates India’s role in global scientific ventures, a point of interest for GS‑1 (India’s scientific heritage) and GS‑3 (science & technology policy). Way Forward Continued monitoring of binary mass‑transfer systems will refine models of stellar rejuvenation and cluster evolution. The IIA plans deeper spectroscopic studies and seeks to identify more such systems using upcoming missions like PLATO . These efforts will strengthen India’s contribution to frontier research and inform policy on funding for large‑scale astronomy projects.