Indian Astronomers Discover Actively Forming Blue Straggler Star

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Key takeaways

Indian astronomers from IIA discovered a Blue Straggler Star (BSS) forming in the binary system TIC 327546480.
First observed by Allan Sandage in 1953 in cluster M3, Blue Stragglers reset their stellar evolutionary clock by gaining hydrogen.
In system TIC 327546480, active mass transfer began about 5.46 billion years ago and continues to keep the star rejuvenated.
Gas transfer generates high temperatures and produces strong X-rays, giving clear proof of active mass accumulation.

Indian astronomers from the Indian Institute of Astrophysics (IIA) and international collaborators discovered a Blue Straggler Star (BSS) actively forming in system TIC 327546480.

A Blue Straggler Star (BSS) is an unusually hot, luminous, blue, and massive star found inside old star clusters.
Standard theories of stellar evolution dictate that high-mass stars should become white dwarfs or red giants long ago, yet these stars appear much younger than surrounding cluster members.

Astronomer Allan Sandage first observed these stars in 1953 inside globular cluster M3, where older stars gain extra hydrogen fuel to reset their nuclear clock.
In binary mass transfer, an aging donor star expands beyond its gravitational limit known as its Roche lobe, leaking matter onto its companion star to make it hotter and bluer.
In stellar collisions within dense cluster cores, two stars physically crash or merge together to fuse their mass into a single rejuvenated star.

These stars defy normal stellar aging by appearing younger and hotter than companion stars formed at the same time in the same cluster.
In the semi-detached binary system TIC 327546480, a smaller companion continuously transfers gas to the larger BSS, causing it to gain mass.
Receiving gas from its companion transfers angular momentum to the BSS, making it spin significantly faster.
Gas striking the star heats up substantially on impact, producing strong X-rays that confirm active mass transfer.
Estimates indicate this mass transfer process started roughly 5.46 billion years ago and continues today.

This discovery provides direct observational proof that mass transfer can rejuvenate aging stars.
The system helps astronomers refine models of binary star evolution, mass dynamics, and stellar life cycles across the universe.