New Observations Reveal WOH G64 Remains a Red Supergiant

Recent spectroscopic observations have provided new insights into WOH G64, a massive star located approximately 160,000 light-years away in the Large Magellanic Cloud. Previously thought to be transitioning into a yellow hypergiant—a phase often preceding a supernova—WOH G64 now appears to retain its red supergiant status.

Between November 2024 and December 2025, astronomers Jacco van Loon of Keele University and Keiichi Ohnaka of Universidad Andrés Bello conducted detailed observations using the Southern African Large Telescope (SALT). Their analysis detected titanium oxide in the star's atmosphere, a molecule typically found in cooler red supergiants. This finding suggests that WOH G64 has not undergone the expected transformation.

"WOH G64 has been claimed to have turned into a yellow hypergiant, which could signal a pre-supernova post-red supergiant evolution," said van Loon. "However, our new spectra obtained with SALT show the hot companion's presence but also clear molecular absorption bands from titanium oxide. This implies that WOH G64 is currently a red supergiant and may never have ceased to be."

The researchers propose that WOH G64 may be part of a binary system, with a smaller, likely blue, companion star interacting with it. This interaction could be influencing the star's behavior and appearance, accounting for previous observations of dimming and the presence of a dusty cocoon.

These findings challenge earlier assumptions about WOH G64's evolutionary path and highlight the complexities involved in predicting the life cycles of massive stars. Continued monitoring is essential to understand the mechanisms driving these changes and to anticipate the star's future developments.