One of the largest known stars in the universe has done something strange – and scientists are debating what it means.

Does the Large Magellanic Cloud’s giant star WOH G64 exist, or did it exist? – One of the largest known red supergiants. More than 1,500 times radius of the sun. In 2013 and 2014, telescopes detected a dramatic change, and the star appeared to be transitioning from a classic red supergiant to a hotter, yellower state.

A team of researchers led by Gonzalo Muñoz Sánchez of the National Observatory of Athens in Greece concluded that the star may have evolved to a rare yellow supergiant stage, taking a step toward its eventual demise.

Publish your research on the preprint server arXiv in November 2024they argued that this change marks an abrupt transition from a red supergiant to a short-lived evolutionary stage that may precede a core-collapse supernova.

“This dramatic change” They write in a currently published paper:“can be explained either by a partial release of a pseudoatmosphere during a common envelope period or by a return to quiescent conditions after a marked eruption with a duration of more than 30 years.”

According to their analysis, the changes included rising temperatures, shrinking in size to about 800 times the solar radius, and changes in atmospheric chemistry. They also identified a hot binary companion star that interacts with a larger, bulging companion star.

However, more recent observations suggest that the star may not have ceased to be a red supergiant at all.

Red supergiants are among the largest stars in the universe by volume and typically evolve from massive stars, about 8 to 30 times the mass of the Sun, that are in the final stages of nuclear combustion. As a red supergiant’s fuel reserves shift to heavier elements, it swells, expanding its outer layer to hundreds of times the radius of the Sun.

Such stars are inherently unstable and can undergo dramatic changes, such as stellar changes. brightness or Huewhen ejecting matter into space.

Located about 160,000 light-years away, WOH G64 is extremely large and widely monitored, providing astronomers with a rare opportunity to observe how massive stars behave in their final evolutionary stages.

However, the behavior of such unstable stars is difficult to interpret. A change in brightness or color does not necessarily mean a change in identity.

The 2024 publication of the paper led by Muñoz Sánchez and his team gives other researchers time to conduct their own follow-up studies before a peer-reviewed version is published in a journal. natural astronomy.

From November 2024 to December 2025, astronomers Jaco van Loon of Keele University in the UK and Keiichi Onaka of Andres Bello University in Chile conducted observations using the South African Large Telescope.

In January 2026, they announced their conclusions in Royal Astronomical Society Monthly Notices. They discovered titanium oxide in the atmosphere of WOH G64.

However, yellow supergiants are too hot to sustain titanium oxide.

“WOH G64 is claimed to have transformed into a yellow supergiant, which may indicate a pre-supernova, post-red supergiant evolution.” van Loon says.

“However, the new spectrum obtained with SALT not only shows the presence of a hot companion, but also shows distinct molecular absorption bands from titanium oxide. This suggests that WOH G64 is now a red supergiant star and may never stop being a red supergiant star.”

Red supergiants exhibiting strange changes that don’t necessarily indicate an impending explosion are not without precedent. After all, who can forget dramatic tantrums? Betelgeuseduring which the brightness decreased almost 25 percent?

Related: First observation of red giant star transitioning to supernova

That doesn’t mean there’s nothing dramatic going on with the star. Van Loon and Ohnaka agree that the star likely has a binary companion. They believe that interactions between the two stars may have complicated their surrounding environment, causing changes similar to spectral shifts without requiring a fundamental evolutionary leap.

Continuous monitoring is important to better understand what is happening with WOH G64. How the star continues to evolve will give scientists a clearer picture of whether the star is at an evolutionary tipping point or whether its current fundamental state is messy.

However, one thing is crystal clear. This strange system is full of surprises and will continue to be a fascinating little corner of the universe.

The paper by Gonzalo Muñoz Sánchez and his team is natural astronomy.