IIA astronomers catch a blue straggler star in the act of forming
Astronomers of the Indian Institute of Astrophysics (IIA) and collaborators reported, on 27 July 2026, a rare blue straggler star caught actively gaining mass from its companion in the binary TIC 327546480 in the old open cluster Collinder 261.
Summary
Blue Straggler Stars (BSS) are stars in clusters that look hotter, brighter and more massive than their peers; the leading theory is that they gain mass from a companion or through mergers. Astronomers of the Indian Institute of Astrophysics, Bengaluru – an autonomous institute of the Department of Science and Technology – studied the binary system TIC 327546480 in the old open star cluster Collinder 261, about 9,500 light-years away. Combining high-precision light curves from NASA's TESS mission with radial-velocity data from ESO's Very Large Telescope in Chile, they found the blue straggler actively gaining material from its companion – direct observational evidence for the mass-transfer theory of BSS formation.
Key facts
- Institute
- Indian Institute of Astrophysics (autonomous institute of DST)
- System studied
- Binary TIC 327546480
- Cluster
- Collinder 261 (old open cluster)
- Distance
- About 9,500 light-years
- Data used
- NASA TESS light curves + ESO Very Large Telescope (Chile) radial velocities
- Finding
- Blue straggler actively gaining mass from its companion
Practice MCQs 3 questions
The blue straggler star reported by IIA in July 2026 was found in which star cluster?
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Correct answer: A — Collinder 261
The binary system TIC 327546480 lies in the old open star cluster Collinder 261, about 9,500 light-years away.
Consider the following statements about the IIA blue straggler study (July 2026): 1. It used light curves from NASA's TESS mission. 2. Radial-velocity data came from ESO's Very Large Telescope in Chile. 3. The star was found to be forming through a collision of two unrelated stars. Which of the statements given above are correct?
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Correct answer: C — 1 and 2 only
The study combined TESS light curves with VLT radial velocities and found the blue straggler actively gaining material from its binary companion (mass transfer), not a collision.
Blue Straggler Stars in a star cluster typically appear, compared with other cluster stars of similar type:
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Correct answer: B — Hotter, brighter and more massive
Blue Straggler Stars appear hotter, brighter and more massive than their peers in the cluster, which is why their origin has long puzzled astronomers.