Astronomers utilizing South Africa’s Southern African Large Telescope (SALT) have settled a high-stakes cosmic debate surrounding WOH G64, one of the most extreme stars ever recorded. Located in the Large Magellanic Cloud, this red supergiant is renowned for its immense luminosity and massive dust clouds. However, recent erratic behaviour, including dramatic dimming and weakened pulsations, led some scientists to believe the star was entering a final, “yellow hypergiant” phase immediately preceding a supernova.
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A research team led by Jacco van Loon and Keiichi Ohnaka used SALT’s Robert Stobie Spectrograph to monitor the star between late 2024 and the end of 2025. Their data revealed a critical signature: titanium oxide molecular bands. Because these bands only exist in cooler environments, their presence confirmed that WOH G64 remains a red supergiant. The star had not transformed into a hotter yellow hypergiant as previously speculated, debunking the theory of an imminent explosion.
The study suggests that WOH G64’s strange behaviour is caused by a hot companion star rather than internal evolution. As this companion orbits closely, its gravitational pull stretches the supergiant’s outer atmosphere. This interaction triggers intense mass loss and the creation of dense dust clouds, which temporarily obscured the star and caused its apparent “fading.”
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Rather than a star on the brink of death, the team describes WOH G64 as a “phoenix rising from the ashes.” The findings, set to be published in the Monthly Notices of the Royal Astronomical Society, highlight the necessity of long-term monitoring to understand the complex final stages of massive stars. By solving this mystery, SALT has provided a clearer picture of how binary star systems influence the life cycles of the universe’s largest suns.
