Long-term observations of WOH G64 — once considered the most extreme red supergiant star in its galaxy — reveal that the star has undergone a dramatic transition, possibly shedding part of its outer layers as it entered a hotter and rarer stellar phase.
An artist’s reconstruction of the red supergiant WOH G64. Image credit: ESO / L. Calçada.
Red supergiants are stars more than 8 times the mass of the Sun and have relatively short lifespans, lasting just 1-10 million years, before they eventually explode as supernovae.
However, the evolution and fate of the most luminous red supergiants remains uncertain.
Since its discovery in the 1980s, WOH G64 has been considered one of the most luminous, largest, and coolest red supergiants in the Large Magellanic Cloud, a dwarf galaxy approximately 160,000 light-years away from our Solar System.
To investigate the evolution of WOH G64, Dr. Gonzalo Muñoz-Sanchez from the National Observatory of Athens and his colleagues reviewed more than 30 years of brightness measurements beginning in 1992, combining them with new and archived electromagnetic spectra.
They found that the star underwent rapid changes, initially dimming in 2011 before recovering and becoming more yellow and warmer — by more than 1,000 degrees Celsius — in 2013-2014.
In 2025, WOH G64 faded considerably and experienced changes to its atmospheric chemistry.
This image, taken by the GRAVITY instrument on ESO’s Very Large Telescope Interferometer, shows the red supergiant WOH G64. Image credit: ESO / Ohnaka et al., doi: 10.1051/0004-6361/202451820.
To explain these developments, the astronomers suggest two potential scenarios.
“Firstly, WOH G64 could be a part of a binary star system in which the red supergiant transitioned into a yellow hypergiant due to an interaction that triggered the ejection of a part of its atmosphere,” they said.
“In an alternative scenario, a yellow hypergiant may have experienced an eruption of material that made it appear red for several decades, ending in 2014.”
“The findings raise the question of whether extreme red supergiants, such as WHO G64, exist because they are interacting binaries, and therefore would not reach these extreme states if they were single stars,” they added.
“Future interactions will determine whether this star explodes as a supernova, collapses into a black hole, or merges with its companion.”
The study was published in the journal Nature Astronomy.
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G. Muñoz-Sanchez et al. The dramatic transition of the extreme red supergiant WOH G64 to a yellow hypergiant. Nat Astron, published online February 23, 2026; doi: 10.1038/s41550-026-02789-7
