Indian astronomers and international collaborators have directly observed a Blue Straggler Star forming in the binary system TIC 327546480, providing direct support for the mass-transfer theory of stellar rejuvenation. According to research published in The Astrophysical Journal Letters, the team used data from NASA’s Transiting Exoplanet Survey Satellite (TESS) and the European Southern Observatory’s Very Large Telescope to capture material flowing between the interacting stars.
Discovery of Forming Blue Straggler Star TIC 327546480
Astronomers studying the old open star cluster Collinder 261 caught a stellar rejuvenation process in real time. Located approximately 9,500 light-years from Earth, the binary system TIC 327546480 shows clear evidence of active mass transfer. Ali Hasan Sheikh, a Ph.D. student at Gauhati University and an INSPIRE Fellow under the Department of Science and Technology, led the international research team.
Blue Straggler Stars (BSS) are unusual objects found within ancient star clusters. They appear hotter, brighter, and more massive than neighboring stars of the same age. For decades, their youthful appearance in clusters estimated to be billions of years old puzzled astrophysicists. This latest observation confirms long-standing theories by showing the formation process actively underway rather than studying it after completion.
Did you know? Collinder 261, the host star cluster for this discovery, is estimated to be around 7 billion years old, yet the mass-transfer process in this specific binary system began approximately 5.46 billion years ago according to evolutionary modelling.
Mechanics of Mass Transfer in Binary Star Systems
The research team combined high-precision light curves from NASA’s TESS mission with radial velocity measurements from the Very Large Telescope in Chile. According to the study, the binary system is semi-detached. One star has expanded beyond its Roche lobe—its gravitational boundary—allowing matter to flow directly onto its companion.
This ongoing accumulation of material causes the receiving star to gain mass and rejuvenate. Detailed analysis revealed that the forming Blue Straggler has a mass roughly 1.67 times that of the Sun. Its companion holds a mass of about 0.32 solar masses. The two stars complete an orbit every 2.11 days, and the Blue Straggler rotates rapidly at approximately 69.55 kilometers per second due to the acquired material.
X-Ray Emission Confirms Active Accretion
To verify that the mass-transfer process is happening right now, researchers looked for high-energy signatures. The team detected strong X-ray emission from the system. According to the study, this X-ray data serves as an independent confirmation that material from the companion star is actively accreting onto the Blue Straggler.
The international effort brought together scientists from the Indian Institute of Astrophysics (IIA), Gauhati University, IUCAA Pune, INAF Italy, LUX Observatoire de Paris, and the University of North Florida.
Frequently Asked Questions
What is a Blue Straggler Star?
Blue Straggler Stars are an unusual class of stars found in star clusters that appear hotter, brighter, and more massive than other stars of the same age, despite belonging to ancient star clusters.
How do Blue Straggler Stars form?
Direct observations of the system TIC 327546480 confirm that Blue Straggler Stars can form through mass transfer in binary star systems, where one star expands and feeds material to its companion.
Where is the binary system TIC 327546480 located?
The system is located about 9,500 light-years from Earth in the old open star cluster Collinder 261.
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