WOH G64 Remains a Red Supergiant Amidst Unusual Behavior

WOH G64, a massive star located approximately 160,000 light-years away in the Large Magellanic Cloud, has exhibited unusual behavior in recent years, leading astronomers to investigate its evolutionary status. Initial observations suggested that the star might have transitioned from a red supergiant to a yellow hypergiant, a phase that often precedes a supernova explosion.

However, a study led by Dr. Jacco van Loon from Keele University, utilizing the Southern African Large Telescope (SALT) between November 2024 and December 2025, has provided new insights. The team detected molecular absorption bands from titanium oxide (TiO) in the star's spectrum, indicating that WOH G64 remains cool enough to be classified as a red supergiant. Dr. van Loon stated, "Our new spectra obtained with SALT show the hot companion's presence but also clear molecular absorption bands from Titanium Oxide (TiO). This implies that WOH G64 is currently a red supergiant and may never have ceased to be."

The study proposes that the star's peculiar behavior is due to interactions with a newly identified companion star. As this companion approaches during its orbit, it exerts tidal forces that stretch WOH G64's atmosphere, leading to the formation of a dust cloud and emission lines from ionized gas. Dr. van Loon explained, "We are essentially witnessing a 'phoenix' rising from the ashes. The atmosphere of the red supergiant is being stretched out by the approach of the companion star, but it has not been stripped altogether. It persists."

These findings highlight the significant impact that binary interactions can have on the evolution and appearance of massive stars. While WOH G64 will eventually end its life in a supernova explosion, current evidence suggests that this event is not imminent.