One of the largest known stars in the universe is doing something strange — and scientists are debating what it means.
Is WOH G64, a massive star in the Large Magellanic Cloud now – or was it? – One of the largest known red supergiants, with a radius over 1,500 times that of the Sun. In 2013 and 2014, telescopes captured a dramatic transition in which the star appeared to transition from a classic red supergiant to a hotter, more yellow state.
The team, led by Gonzalo Muñoz Sánchez of the National Observatory in Athens, Greece, concluded that the star has evolved into a rare yellow supergiant stage, potentially taking a step towards its ultimate demise.
They presented their research on the preprint server arXiv in November 2024, arguing that this change marks an abrupt transition from a red supergiant to a brief evolutionary stage that may precede a core-collapse supernova.
“This dramatic transition could be explained by a partial ejection of the pseudoatmosphere during the co-envelope phase, or by a return to a quiescent state after a prominent eruption lasting more than 30 years,” they write in their now-published paper.
According to their analysis, these changes include increases in temperature, a reduction in size to about 800 solar radii, and changes in the chemical composition of the atmosphere. They also discovered a hot binary companion interacting with its larger, more bloated companion.
But recent observations suggest the star may never stop becoming a red supergiant.
Red supergiants are among the largest stars in the universe, evolving from massive stars that are in the final stages of nuclear combustion, typically about 8 to 30 times the mass of the sun. As a red supergiant’s fuel reserves shift toward heavier elements, it expands, expanding its outer layers to hundreds of times the radius of the Sun.
These stars are inherently unstable and can undergo dramatic changes, including changes in brightness or hue, as they shed material into space.
Located about 160,000 light-years away, WOH G64 is exceptionally large and widely monitored, providing astronomers with a rare opportunity to observe the behavior of massive stars in their final stages of evolution.
But explaining the behavior of such unstable stars is difficult. A change in brightness or color does not necessarily mean a change in identity.
The paper led by Muñoz-Sanchez and his team is due to be released in 2024, giving other researchers time to make their own follow-up observations before a peer-reviewed version is published. natural astronomy.
Astronomers Jacco van Loon of Keele University in the UK and Keiichi Ohnaka of Andrés Bello University in Chile conducted observations using the Southern Africa Large Telescope between November 2024 and December 2025.
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In January 2026, they performed in ” Royal Astronomical Society monthly notices. They found titanium oxide in the atmosphere of WOH G64.
However, yellow supergiants are too hot to sustain the presence of titanium oxide.
“WOH G64 is said to have transformed into a yellow supergiant, which may mark the evolution of a red supergiant before a supernova,” said Van Loon.
“However, the new spectrum we obtained with SALT shows the presence of a hot companion, but also shows a clear molecular absorption band of titanium oxide. This means that WOH G64 is currently a red supergiant and may never stop doing so.”
It’s not unprecedented for a red supergiant star to exhibit strange behavior that doesn’t necessarily indicate an impending explosion. After all, who could forget Betelgeuse’s violent tantrum, during which its brightness dropped by nearly 25%?
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That doesn’t mean there hasn’t been any drama going on with the star. Van Loon and Onaka agreed that the star might have a binary companion. They believe that interactions between two stars could complicate the environment around them, producing changes similar to spectral changes without requiring a fundamental evolutionary leap.
In order to better understand the situation of WOH G64, continuous monitoring is crucial. How it continues to evolve will give scientists a clearer picture of whether the star is on the edge of an evolutionary transition, or whether chaos is its current baseline state.
However, one thing remains clear. This strange system is full of surprises and continues to be a fascinating little corner of the universe.
The paper by Gonzalo Muñoz-Sanchez and his team was published in natural astronomy.
