WOH G64 is no ordinary star. Located in the Large Magellanic Cloud, a satellite galaxy orbiting the Milky Way, this red supergiant star holds multiple records as the brightest, coldest, and dustiest galaxy in the galaxy. These star beasts live fast and die young, ending their short lives in devastating supernova explosions that temporarily outstrip the entire galaxy.

However, since a few years ago, WOH G64 has become quite faded and its characteristic pulsation has weakened significantly. Most interestingly, its spectrum has changed radically, switching from cold absorption features typical of red supergiants to emission from hot ionized gas. When astronomers discovered that a newly formed dust cloud was obscuring the star in 2024, many wondered if they were witnessing a rare evolutionary leap into the yellow supergiant stage, a brief, unstable stage that can occur just before a supernova explosion.

The Large Magellanic Cloud, home to WOH G64 (Credit: ESO/VMC research)

Yellow supergiants are extremely rare, with only a handful known, and likely represent a fleeting transitional phase lasting only a few thousand years. If WOH G64 had truly transformed, astronomers would have had a front row seat to the star’s final act before its explosive demise.

Dr Jacco van Loon of Kiel University and his international team were not convinced. From November 2024 to December 2025, they used the South African Large Telescope to obtain detailed optical spectra of the fading system. What they discovered definitively answered that question.

Hidden within these spectra are absorption bands from titanium oxide molecules, proving that WOH G64 remains hot enough to be a red supergiant star. However, these molecules cannot survive in the high temperatures of yellow supergiants. The stars had not evolved, but somehow gained allies.

A new scenario seems to explain everything. WOH G64 does not exist alone, but in a binary system with a smaller, hotter companion star. When this companion star approaches in its orbit, it stretches the red supergiant’s atmosphere outward, spreading stellar material throughout the system. Some of this material forms a disk around the hot companion star, producing ionizing emission lines that baffle astronomers. A newly formed dust cloud? Probably created by material escaping from a destroyed atmosphere.

“We are essentially witnessing a ‘phoenix’ rising from the ashes. The atmosphere of a red supergiant star is being dramatically altered by binary interactions, but the star itself maintains its current evolutionary stage.” Dr Jacco van Loon from the University of Kiel

The findings highlight how binary relatives can produce surprising changes that mimic evolutionary transitions. WOH G64 will eventually explode as a supernova, but the drama remains a future event rather than an immediate one for now.

sauce : A team led by Kiel reveals that the massive star WOH G64 is still a red supergiant star