Massive Star Puzzles Scientists with Unprecedented Color Change

Astronomers are baffled by a giant star called WOH G64 that dramatically changed from red to yellow in 2014, defying current scientific models. The star, located 160,000 light-years from Earth, is 28 times more massive than our sun and appears to be nearing the end of its relatively short lifespan.

Astronomers are scratching their heads over a colossal star that has done something never witnessed before in the cosmos.

The star, known as WOH G64, sits in the Large Magellanic Cloud – a neighboring galaxy to our own Milky Way. Scientists have been watching this stellar giant for more than 30 years, and what they’ve seen has left them puzzled.

In 2014, researchers noticed something extraordinary: the star suddenly shifted from red to yellow, indicating its surface temperature had increased. This transformation happened without any explosive event or eruption that scientists would typically expect.

“Typically the evolution of a star takes place on timescales of billions of years. On human timescales, we only observe more abrupt and violent events, such as eruptions, the merger of two stars or their explosive deaths,” explained astronomer Gonzalo Muñoz-Sanchez, who led the research published in Nature Astronomy.

The star had previously been categorized as an extreme red supergiant but quickly transformed into what scientists call a yellow hypergiant – a change that happened rapidly by cosmic standards.

“No current stellar models can fully explain this transformation” in WOH G64, Muñoz-Sanchez noted. He conducted the study while working at the National Observatory of Athens.

To put this star’s immense size in perspective, WOH G64 weighs 28 times more than our sun and shines 300,000 times brighter. Its diameter stretches 1,500 times wider than the sun. If this giant replaced our sun, its outer edge would reach somewhere between Jupiter and Saturn’s orbital paths. Even traveling at light speed, it would take six hours to go around the star’s perimeter.

At roughly 10 million years old, WOH G64 is approaching its final chapter. By comparison, our sun has been burning for 4.5 billion years and has another 5 billion years ahead of it. The massive star lies approximately 160,000 light-years away from Earth.

“WOH G64 is a massive star and very different from the sun,” Muñoz-Sanchez emphasized.

Scientists understand that stars weighing between eight and 23 times our sun’s mass typically become red supergiants before exploding as supernovas. However, the destiny of stars in the 23 to 30 solar mass range remains uncertain. They might explode as supernovas, collapse directly into black holes, or transition from red supergiants to yellow hypergiants before their demise.

“Hence, WOH G64 might be the solution to this question,” Muñoz-Sanchez suggested.

The mystery deepens further because observations reveal WOH G64 is gravitationally linked to another star in what astronomers call a binary system. Researchers couldn’t determine the companion star’s size or properties, but they believe the two might eventually merge.

Scientists have developed theories about WOH G64’s recent changes. One possibility is that the star experienced a violent episode before their observations began, which turned it red, and it’s now returning to its normal yellow state. Another theory suggests that interactions between WOH G64 and its companion temporarily made it appear like a red supergiant.

“As astronomers continue to monitor this remarkable system, WOH G64 is poised to reshape our understanding of how the most massive stars live and die,” Muñoz-Sanchez concluded.