Giant Star's Mystery Changes Thrill Astronomers in Real Time

For the first time ever, astronomers are watching a massive star transform before their eyes on a timescale humans can actually observe.

WOH G64, a red supergiant star visible from the Southern Hemisphere, has puzzled scientists for decades. It's more than 1,500 times larger than our Sun and blasts out over 100,000 times more energy.

Scientists thought this stellar giant would steadily fade over millions of years. But recently, something unexpected started happening.

In just the last decade, the star began dimming rapidly and apparently shrinking. It started pulsating differently and appeared to grow warmer, leading some researchers to wonder if it was transforming into a rare yellow hypergiant.

A team using the Southern African Large Telescope (SALT) made a breakthrough discovery this year. They found evidence that WOH G64 might not be alone after all.

The observations revealed both hot ionized gas and cool molecules near the star, a combination that doesn't make sense for a single star. The best explanation? WOH G64 has a smaller, hotter blue companion star that astronomers have suspected for years but never confirmed.

This hidden companion might be causing all the dramatic changes. If its orbit is elongated rather than circular, the blue star could have recently swooped closer to its giant red sibling.

The blue star's gravity may be stretching out the red supergiant's atmosphere, making it more transparent. This would explain why we're seeing warmer interior layers while cool molecular patches remain in spots.

In 2024, researchers captured the sharpest picture ever taken of a star in another galaxy. The image revealed fresh dust clouds near WOH G64, showing the star was ejecting far more material than before.

Why This Inspires

Stars usually change on timescales of millions of years, far beyond human lifespans to witness. WOH G64 is offering scientists a rare front-row seat to stellar evolution happening right now.

The discovery shows how international collaboration and advanced telescopes in Africa are unlocking cosmic mysteries. The Southern African Large Telescope played a crucial role in solving this puzzle, demonstrating how scientific infrastructure on the African continent contributes to our understanding of the universe.

Researchers are watching closely to see if the star will return to its former glory as the companion orbits away, or if it has permanently shed its outer layers. Either way, they're witnessing something no human has seen before: a supergiant star's dramatic transformation in real time.