BENGALURU: In a discovery that reads like celestial fiction, astronomers have uncovered evidence of a “vampire star” rejuvenating itself by feeding on a companion star in the “M67” star cluster. This finding, made possible by India’s AstroSat space observatory, provides a rare glimpse into the complex world of binary star evolution and stellar rejuvenation.
The research, conducted by a team from the Indian Institute of Astrophysics (IIA), focuses on a peculiar class of stars known as blue stragglers. These stars, found in clusters, appear younger than their neighbours, defying simple models of stellar evolution. The mystery behind their youthful appearance has long puzzled astronomers, with theories suggesting they might be consuming material from companion stars.
At the heart of this cosmic drama is “WOCS 9005”, a star residing in M67, an open cluster in the constellation Cancer. Using spectroscopic data from the Galah (Galactic Archaeology with Hermes) survey, researchers discovered that WOCS 9005’s atmosphere is unusually rich in heavy elements such as barium, yttrium, and lanthanum. These elements are typically associated with much older, more massive stars in their final stages of life.
“This star is expected to show chemistry very similar to our Sun, but we found that its atmosphere is rich in heavy elements. This chemical anomaly pointed to a fascinating possibility: WOCS 9005 had been “polluted” by material from a companion star,” Harshit Pal, the study’s lead author.
The plot thickened when the team turned to AstroSat, India’s first dedicated space observatory. Using its Ultraviolet Imaging Telescope (UVIT), they detected significant ultraviolet emissions from WOCS 9005. This was unexpected for a star with a temperature similar to Sun, suggesting the presence of a hot, compact companion – likely the remnant of the donor star.
“The blue straggler star that we see now must have eaten up most of this barium-rich material due to its gravitational pull, and is now presenting itself as a rejuvenated star,” said Prof Annapurni Subramaniam, Director of IIA and co-author of the paper.
This discovery marks the first time scientists have observed both a chemically enriched blue straggler and the remnant of its donor star in a cluster environment. It provides compelling evidence for the mass transfer theory of blue straggler formation and offers a rare glimpse into the life cycle of binary star systems.
The implications of this finding extend beyond the realm of stellar evolution. The heavy elements observed in WOCS 9005 are created through a process called s-process nucleosynthesis, responsible for producing about half of the atomic nuclei heavier than iron in the universe. Understanding how these elements are distributed through stellar interactions contributes to our knowledge of cosmic chemical enrichment.
Bala Sudhakara Reddy, a co-author of the study, noted that WOCS 9005 is the first “barium blue straggler” discovered in M67, adding another layer of significance to the finding.
The research, set to be published in The Astrophysical Journal Letters, not only solves a long-standing astronomical puzzle but also showcases the capabilities of India’s space programme. AstroSat’s ability to detect the faint UV emissions from the white dwarf companion proved crucial in piecing together this cosmic narrative.
The research, conducted by a team from the Indian Institute of Astrophysics (IIA), focuses on a peculiar class of stars known as blue stragglers. These stars, found in clusters, appear younger than their neighbours, defying simple models of stellar evolution. The mystery behind their youthful appearance has long puzzled astronomers, with theories suggesting they might be consuming material from companion stars.
At the heart of this cosmic drama is “WOCS 9005”, a star residing in M67, an open cluster in the constellation Cancer. Using spectroscopic data from the Galah (Galactic Archaeology with Hermes) survey, researchers discovered that WOCS 9005’s atmosphere is unusually rich in heavy elements such as barium, yttrium, and lanthanum. These elements are typically associated with much older, more massive stars in their final stages of life.
“This star is expected to show chemistry very similar to our Sun, but we found that its atmosphere is rich in heavy elements. This chemical anomaly pointed to a fascinating possibility: WOCS 9005 had been “polluted” by material from a companion star,” Harshit Pal, the study’s lead author.
The plot thickened when the team turned to AstroSat, India’s first dedicated space observatory. Using its Ultraviolet Imaging Telescope (UVIT), they detected significant ultraviolet emissions from WOCS 9005. This was unexpected for a star with a temperature similar to Sun, suggesting the presence of a hot, compact companion – likely the remnant of the donor star.
“The blue straggler star that we see now must have eaten up most of this barium-rich material due to its gravitational pull, and is now presenting itself as a rejuvenated star,” said Prof Annapurni Subramaniam, Director of IIA and co-author of the paper.
This discovery marks the first time scientists have observed both a chemically enriched blue straggler and the remnant of its donor star in a cluster environment. It provides compelling evidence for the mass transfer theory of blue straggler formation and offers a rare glimpse into the life cycle of binary star systems.
The implications of this finding extend beyond the realm of stellar evolution. The heavy elements observed in WOCS 9005 are created through a process called s-process nucleosynthesis, responsible for producing about half of the atomic nuclei heavier than iron in the universe. Understanding how these elements are distributed through stellar interactions contributes to our knowledge of cosmic chemical enrichment.
Bala Sudhakara Reddy, a co-author of the study, noted that WOCS 9005 is the first “barium blue straggler” discovered in M67, adding another layer of significance to the finding.
The research, set to be published in The Astrophysical Journal Letters, not only solves a long-standing astronomical puzzle but also showcases the capabilities of India’s space programme. AstroSat’s ability to detect the faint UV emissions from the white dwarf companion proved crucial in piecing together this cosmic narrative.
