In-depth observations of WOH G64, previously regarded as the most extreme red supergiant star in our galaxy, have uncovered significant changes, suggesting it may have shed parts of its outer layers while transitioning into a hotter, rarer stellar phase.
Red supergiant stars, exceeding eight times the mass of the Sun, boast relatively short lifespans of merely 1 to 10 million years before culminating in a spectacular supernova explosion.
Despite their brightness, the evolutionary trajectories and ultimate fates of the universe’s most luminous red supergiants remain unclear.
Discovered in the 1980s, WOH G64 has been recognized as one of the brightest, largest, and coolest red supergiants within the Large Magellanic Cloud, a dwarf galaxy located approximately 160,000 light-years from Earth.
To explore the evolution of WOH G64, Dr. Gonzalo Muñoz Sánchez from the National Astronomical Observatory of Athens and his team analyzed over 30 years of brightness data, commencing in 1992, using both recent and archived electromagnetic spectra.
The research indicated that the star experienced rapid fluctuations: it dimmed in 2011, then rebounded, transforming into a yellower hue and increasing in temperature by over 1,000 degrees Celsius between 2013 and 2014.
In 2025, WOH G64 experienced a significant dimming, accompanied by alterations in its atmospheric chemistry.
This image, captured by ESO’s Very Large Telescope Interferometer’s GRAVITY instrument, showcases the red supergiant star WOH G64. Image credit: ESO/Ohnaka et al., doi: 10.1051/0004-6361/202451820.
Astronomers have proposed two possible explanations for these developments.
“First, WOH G64 could be part of a binary system where a red supergiant star transformed into a yellow supergiant due to interactions that expelled part of its atmosphere,” the researchers noted.
“Alternatively, the yellow supergiant may have experienced an eruption of red material lasting several decades, culminating in 2014.”
“This discovery raises intriguing questions about the nature of extreme red supergiants like WOH G64 and whether they are predominantly interacting binaries, which might prevent single stars from reaching such extreme conditions,” the researchers concluded.
The future interactions of WOH G64 will ultimately determine whether it explodes as a supernova, collapses into a black hole, or merges with a companion star.
For further details, refer to the study published in the journal Nature Astronomy.
_____
G. Munoz-Sanchez et al. A dramatic transformation from the very red supergiant WOH G64 to a yellow supergiant. Nat Astron, published online on February 23, 2026. doi: 10.1038/s41550-026-02789-7
Source: www.sci.news
